• The Korean Journal of Nuclear Medicine
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• v.32 no.2
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• pp.121-128
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• 1998

Purpose: $Na^+-K^+$ ATPase activity has been estimated by the degree of inhibition of cation transport by cardiac glycosides (ouabain) using Rb-86 as a substrate. The biological characteristisc of T1-201 is known to be similar to those of potassium as a transport substrate in the presence of glucose, insulin or phobol myristate acetate (PMA). The purpose of this study was to measure ouabain sensitive $Na^+-K^+$ ATPase activity using T1-201 and compare with that using Rb-86. Materials and Methods: Smooth muscle cells isolated from rat aorta or human placental umbilical artery were cultured, and used to measure cellular $Na^+-K^+$ ATPase activity. $Na^+-K^+$ ATPase activity was measured as a percentage decrease in cellular uptake of T1-201 or Rb-86 by ouabain under the presence of glucose, insulin or PMA in media. Results: $Na^+-K^+$ ATPase activity measured with T1-201, as a transport substrate, was not different from those measured with Rb-86 in rat or human smooth muscle cell preparation. Incubation with high concentration glucose resulted in about 30% decrease in enzyme activity. In contrast, insulin or PMA resulted in 10-70% or 28% increases from baseline activity, respectively. Conclusion: These results suggests that 71-201 could replace Rb-86 in measurement of ouabain sensitive $Na^+-K^+$ ATPase activity in vitro. High level of glucose concentration decreased cellular $Na^+-K^+$ ATPase activity, but insulin or PMA increased it.

• The Korean Journal of Pharmacology
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• v.10 no.1 s.15
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• pp.31-40
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• 1974

1. The authors investigated the effects of $PGE_1$ on the action of sympathomimetics in the vas deferens of guinea-pig, comparing with those in the rat vas deferens, and also the action of $PGE_1$ on the motility of nerve-free smooth muscle of chick amnion. 2. In the isolated guinea-pig vas deferens, the actions of phenylephrine and norepinephrine were much potentiated by pretreatment with $PGE_1$. Futher, in the isolated hypogastric nerve-vas deferens preparation of guinea-pig, effects of phenylephrine, norepinephrine and tyramine on the contractile response of vas to the hypogastric nerve stimulation and to the transmural stimulation were also augumented especially in tension by $PGE_1$-pretreatment. 3. In the isolated hypogastric nerve-vas preparation of rat, both contractile responses to hypogastric nerve and transmural stimulation were slowly reduced by treatment with $PGE_1$ and the potentiated effect of phenylephrine or norepinephrine was not observed in spite of pretreatment with $PGE_1$. 4. The actions of phenylephrine and norepinephrine on the denervated vas deferens of guinea-pig were also enhanced by $PGE_1$ as it were in the intact vas deferens, but there was no significant effect by $PGE_1$ on the action of norepinephrine in the denervated rat vas deferens. 5. $PGE_1$ in low concentration $(10^{-8}g/ml)$ did not affect the spontaneous motility of nerve-free smooth muscle of chick amnion ($9{\sim}11$ th day incubated chick), but in large concentration $(5{\times}10^{-8}g/ml)$ it caused irregular and slightly inhibitory movement. Pretreatment with $PGE_1$ on chick amnion did not exert any change on the action of phenylephrine applied. However, the stimulatory action of physostigmine on the chick amnion was a little antagonized by the low concentration of $PGE_1$. 6. It might be summarized that there is species difference between the actions of $PGE_1$ on the vas deferens of guinea-pig and that of rat, and the action of $PGE_1$ on the guinea-pig vas deferens might be mediated by the other mechanism rather than by direct action on the vas musculature.

• Journal of Life Science
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• v.28 no.12
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• pp.1516-1522
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• 2018

Atherosclerosis is an obstructive vessel disease mainly caused by chronic arterial inflammation to which the proliferation and migration of vascular smooth muscle cells (VSMCs) is the main pathological response. In the present study, the primary responsible inflammatory cytokine and its signaling pathway was investigated. The proliferation and migration of VSMCs was significantly enhanced by the prostaglandin $F_{2{\alpha}}$ ($PGF_{2{\alpha}}$), while neither was affected by tumor necrosis factor ${\alpha}$. Prostacyclin $I_2$ was seen to enhance the proliferation of VSMCs while simultaneously suppressing their migration. Both prostaglandin $D_2$ and prostaglandin $E_2$ significantly enhanced the migration of VSMCs, however, proliferation was not affected by either of them. The proliferation and migration of VSMCs stimulated by $PGF_{2{\alpha}}$ progressed in a dose-dependent manner; the $EC_{50}$ value of both proliferation and migration was $0.1{\mu}M$. VSMCs highly expressed the phospholipase isoform $C-{\beta}3$ ($PLC-{\beta}3$) while others such as $PLC-{\beta}1$, $PLC-{\beta}2$, and $PLC-{\beta}4$ were not expressed. Inhibition of the PLCs by U73122 completely blocked the $PGF_{2{\alpha}}$-induced migration of VSMCs, and, in addition, silencing $PLC-{\beta}3$ significantly diminished the $PGF_{2{\alpha}}$-induced proliferation and migration of VSMCs. Given these results, we suggest that $PGF_{2{\alpha}}$ plays a crucial role in the proliferation and migration of VSMCs, and activation of $PLC-{\beta}3$ could be involved in their $PGF_{2{\alpha}}$-dependent migration.

• Journal of Life Science
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• v.32 no.12
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• pp.962-970
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• 2022

Nonalcoholic steatohepatitis (NASH) is the progressive stage of nonalcoholic fatty liver disease (NAFLD) that highly increases the risk of cirrhosis and liver cancer, and there are few therapeutic options available in the clinic. Poricoic acid (PoA), a component of Poria cocos Wolf, has a wide range of pharmacological activities; however, little is known about its effects on NASH. The preventive effects of PoA on NASH were examined in vivo and in vitro by analyzing triglyceride synthesis, inflammation and fibrosis. In the high fat and methionine-choline deficient diet (HFMCD)-induced NASH mice, PoA reduced the liver weight and the levels of alanine aminotransferase and aspartate aminotransferase compared with non-treated HFMCD group. The staining with Oil Red O and hematoxylin and eosin revealed that PoA administration reduced red staining and the size of lipid droplet. qPCR analysis showed that PoA also reduced the expression of genes related to triglyceride synthesis. Further, immunostaining with CD68 and qPCR analysis revealed that PoA reduced the staining with CD68 and the expression of inflammatory genes induced by HFMCD. Moreover, PoA reduced the staining with sirius red and antibody of α-smooth muscle actin and also reduced the expression of genes related to fibrosis. The treatment of PoA to AML12 cells reduced the increase in triglyceride amount and expression of genes associated with triglyceride synthesis, inflammation and fibrosis. Taken together, our study indicate that PoA has therapeutic effect on NASH through preventing triglyceride synthesis, inflammation and fibrosis.

• The Korean Journal of Pharmacology
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• v.16 no.2 s.27
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• pp.55-70
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• 1980

The pharmacological and microbiological studies of Cefoperazone (T-1551, Toyama Chemical Co., Japan) were conducted in vitro and in vivo. The studies included stability and physicochemical characteristics, antimicrobial activity, animal and human pharmacokinetics, animal pharmacodynamics and safety evaluation of Cefoperazone sodium for injection. 1) Stability and physicochemical characteristics. Sodium salt of cefoperazone for injection had a general appearance of white crystalline powder which contained 0.5% water, and of which melting point was $187.2^{\circ}C$. The pH's of 10% and 25% aqueous solutions were 5.03 ana 5.16 at $25^{\circ}C$. The preparations of cefoperazone did not contain any pyrogenic substances and did not liberate histamine in cats. The drug was highly compatible with common infusion solutions including 5% Dextrose solution and no significant potency decrease was observed in 5 hours after mixing. Powdered cefoperazone sodium contained in hermetically sealed and ligt-shielded container was highly stable at $4^circ}C{\sim}37^{\circ}C$ for 12 weeks. When stored at $4^{\circ}C$ the potency was retained almost completely for up to one year. 2) Antimicrobial activity against clinical isolates. Among the 230 clinical isolates included, Salmonella typhi was the most susceptible to cefoperazone, with 100% inhibition at MIC of ${\leq}0.5{\mu}g/ml$. Cefoperazone was also highly active against Streptococcus pyogenes(group A), Kletsiella pneumoniae, Staphylococcus aureus and Shigella flexneri, with 100% inhibition at $16{\mu}g/ml$ or less. More than 80% of Escherichia coli, Enterobacter aerogenes and Salmonella paratyphi was inhibited at ${\leq}16{\mu}/ml$, while Enterobacter cloaceae, Serratia marcescens and Pseudomonas aerogenosa were somewhat less sensitive to cefoperagone, with inhibitions of 60%, 55% and 35% respectively at the same MIC. 3) Animal pharmacokinetics Serum concentration, organ distritution and excretion of cefoperazone in rats were observed after single intramuscular injections at doses of 20 mg/kg and 50 mg/kg. The extent of protein binding to human plasma protein was also measured in vitro br equilibrium dialysis method. The mean Peak serum concentrations of $7.4{\mu}g/ml$ and $16.4{\mu}/ml$ were obtained at 30 min. after administration of cefoperazone at doses of 20 mg/kg and 50 mg/kg respectively. The tissue concentrations of cefoperazone measured at 30 and 60 min. were highest in kidney. And the concentrations of the drug in kidney, liver and small intestine were much higher than in blood. Urinary and fecal excretion over 24 hours after injetcion ranged form 12.5% to 15.0% in urine and from 19.6% to 25.0% in feces, indicating that the gastrointestinal system is more important than renal system for the excretion of cefoperazone. The extent of binding to human plasma protein measured by equilibrium dialysis was $76.3%{\sim}76.9%$, which was somewhat lower than the others utilizing centrifugal ultrafiltration method. 4) Animal pharmacodynamics Central nervous system : Effects of cefoperazone on the spontaneous movement and general behavioral patterns of rats, the pentobarbital sleeping time in mice and the body temperature in rabbits were observed. Single intraperitoneal injections at doses of $500{\sim}2,000mg/kg$ in rats did not affect the spontaneous movement ana the general behavioral patterns of the animal. Doses of $125{\sim}500mg/kg$ of cefoperazone injected intraperitonealy in mice neither increased nor decreased the pentobarbital-induced sleeping time. In rabbits the normal body temperature was maintained following the single intravenous injections of $125{\sim}2,000mg/kg$ dose. Respiratory and circulatory system: Respiration rate, blood pressure, heart rate and ECG of anesthetized rabbits were monitored for 3 hours following single intravenous injections of cefoperazone at doses of $125{\sim}2,000mg/kg$. The respiration rate decreased by $3{\sim}l7%$ at all the doses of cefoperazone administered. Blood pressure did not show any changes but slight decrease from 130/113 to 125/107 by the highest dose(2,000 mg/kg) injected in this experiment. The dosages of 1,000 and 2,000 mg/kg seemed to slightly decrease the heart rate, but it was not significantly different from the normal control. All the doses of cefoperazone injected were not associated with any abnormal changes in ECG findings throughout the monitering period. Autonomic nervous system and smooth muscle: Effects of cefoperazone on the automatic movement of rabbit isolated small intestine, large intestine, stomach and uterus were observed in vitro. The autonomic movement and tonus of intestinal smooth muscle increased at dose of $40{\mu}g/ml$ in small intestine and at 0.4 mg/ml in large intestine. However, in stomach and uterine smooth muscle the autonomic movement was slightly increased by the much higher doses of 5-10 mg/ml. Blood: In vitro osmotic fragility of rabbit RBC suspension was not affected by cefoperazone of $1{\sim}10mg/ml$. Doses of 7.5 and 10 mg/ml were associated with 11.8% and 15.3% prolongation of whole blood coagulation time. Liver and kidney function: When measured at 3 hours after single intravenous injections of cefoperaonze in rabbits, the values of serum GOT, GPT, Bilirubin, TTT, BUN and creatine were not significantly different from the normal control. 5) Safety evaluation Acute toxicity: The acute toxicity of cefoperazone was studied following intraperitoneal and intravenous injections to mice(A strain, 4 week old) and rats(Sprague-Dawler, 6 week old). The LD_(50)'s of intraperitonealy injected cefoperazone were 9.7g/kg in male mice, 9.6g/kg in female mice and over 15g/kg in both male and female rats. And when administered intravenously in rats, LD_(50)'s were 5.1g/kg in male and 5.0g/kg in female. Administrations of the high doses of the drug were associated with slight inhibition of spontaneous movement and convulsion. Atdominal transudate and intestinal hyperemia were observed in animals administered intraperitonealy. In rats receiving high doses of the drug intravenously rhinorrhea and pulmonary congestion and edema were also observed. Renal proximal tubular epithelial degeneration was found in animals dosing in high concentrations of cefoperazone. Subacute toxicity: Rats(Sprague-Dawley, 6 week old) dosing 0.5, 1.0 and 2.0 g/kg/day of cefoperazone intraperitonealy were observed for one month and sacrificed at 24 hours after the last dose. In animals with a high dose, slight inhibition of spontaneous movement was observed during the experimental period. Soft stool or diarrhea appeared at first or second week of the administration in rats receiving 2.0g/kg. Daily food consumption and weekly weight gain were similar to control during the administration. Urinalysis, blood chemistry and hematology after one month administration were not different from control either. Cecal enlargement, which is an expected effect of broad spectrum antibiotic altering the normal intestinal microbial flora, was observed. Intestinal or peritoneal congestion and peritonitis were found. These findings seemed to be attributed to the local irritation following prolonged intraperitoneal injections of hypertonic and acidic cefoperazone solution. Among the histopathologic findings renal proximal tubular epithelial degeneration was characteristic in rats receiving 1 and 2g/kg/day, which were 10 and 20 times higher than the maximal clinical dose (100 mg/kg) of the drug. 6) Human pharmacokinetics Serum concentrations and urinary excretion were determined following a single intravenous injection of 1g cefoperazone in eight healthy, male volunteers. Mean serum concentrations of 89.3, 61.3, 26.6, 12.3, 2.3, and $1.8{\mu}g/ml$ occured at 1,2,4,6,8 and 12 hours after injection respectively, and the biological half-life was 108 minutes. Urinary excretion over 24 hours after injection was up to 43.5% of administered dose.

• Journal of Chest Surgery
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• v.37 no.3
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• pp.210-219
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• 2004

Extracellular $K^{+}$ concentration ([ $K^{+}$]$_{0}$ ) can be increased within several mM by the efflux of intracellular $K^{+}$. To investigate the effect of an increase in [ $K^{+}$]$_{0}$ on vascular contractility, we attempted to examine whether extracellular $K^{+}$ might modulate vascular contractility, endothelium-dependent relaxation (EDR) and intracellular $Ca^2$$^{+}$ concentration ([C $a^2$$^{+}$]$_{i}$ ) in endothelial cells (EC). We observed isometric contractions in rabbit carotid, superior mesenteric, basilar arteries and movse aorta. [C $a^2$$^{+}$]$_{i}$ was recorded by microfluorimeter using Fura-2/AM in EC. No change in contractility was recorded by the increase in [ $K^{+}$]$_{0}$ from 6 to 12 mM in conduit artery such as rabbit carotid artery. whereas resistant vessels, such as basilar and branches of superior mesenteric arteries (SMA), were relaxed by the increase. In basilar artery, the relaxation by the increase in [ $K^{+}$]$_{0}$ to from 1 to 3 mM was bigger than that by the increase from 6 to 12 mM. In contrast, in branches of SMA, the relaxation by the increase in [ $K^{+}$]$_{0}$ to from 6 to 12 mM is bigger than that by the increase from 1 to 3 mM. $Ba^2$$^{+}$ (30 $\mu$M) did not inhibit the relaxation by the increase in [ $K^{+}$]$_{0}$ from 1 to 3 mM but did inhibit the relaxation by the increase from 6 to 12 mM. In the mouse aorta without the endothelium or treated with $N^{G}$_nitro-L-arginine (30 $\mu$M), nitric oxide synthesis blocker, the increase in [ $K^{+}$]$_{0}$ from 6 to 12 mM did not change the magnitude of contraction induced either norepinephrine or prostaglandin $F_2$$_{\alpha}$. The increase in [ $K^{+}$]$_{0}$ up to 12 mM did not induce contraction of mouse aorta but the increase more than 12 mM induced contraction. In the mouse aorta, EDR was completely inhibited on increasing [ $K^{+}$]$_{0}$ from 6 to 12 mM. In cultured mouse aorta EC, [C $a^2$$^{+}$]$_{i}$ , was increased by acetylcholine or ATP application and the increased [C $a^2$$^{+}$]$_{i}$ , was reduced by the increase in [ $K^{+}$]$_{0}$ reversibly and concentration-dependently. In human umbilical vein EC, similar effect of extracellular $K^{+}$ was observed. Ouabain, a N $a^{+}$ - $K^{+}$ pump blocker, and N $i^2$$^{+}$, a N $a^{+}$ - $Ca^2$$^{+}$ exchanger blocker, reversed the inhibitory effect of extracellular $K^{+}$. In resistant arteries, the increase in [ $K^{+}$]$_{0}$ relaxes vascular smooth muscle and the underlying mechanisms differ according to the kinds of the arteries; $Ba^2$$^{+}$-insensitive mechanism in basilar artery and $Ba^2$$^{+}$ -sensitive one in branches of SMA. It also inhibits [C $a^2$$^{+}$]$_{i}$ , increase in EC and thereby EDR. The initial mechanism of the inhibition may be due to the activation of N $a^{+}$ - $K^{+}$pump. activation of N $a^{+}$ - $K^{+}$pump.p.p.p.

• Tuberculosis and Respiratory Diseases
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• v.49 no.4
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• pp.486-494
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• 2000

Background : The dominant innervation of airway smooth muscle is parasympathetic fibers which are carried in the vagus nerve. Activation of these cholinergic nerves releases acetylcholine which binds to $M_3$ muscarinic receptors on the smooth muscle causing bronchocontraction. Acetylcholine also feeds back onto neuronal $M_2$ muscarinic receptors located on the postganglionic cholinergic nerves. Stimulation of these receptors further inhibits acetylcholine release, so these $M_2$, muscarinic receptors act as autoreceptors. Loss of function of these $M_2$ receptors, as it occurs in animal models of hyperresponsiveness, leads to an increase in vagally mediated hyperresponsiveness. However, there are limited data pertaining to whether there are dysfunctions of these receptors in patients with asthma. The aim of this study is to determine whether there are dysfunction of $M_2$ muscarinic receptors in asthmatic patients and difference of function of these receptors according to severity of asthma. Method : We studied twenty-seven patients with asthma who were registered at Pulmonology Division of Korea University Hospital. They all met asthma criteria of ATS. Of these patients, eleven patients were categorized as having mild asthma, eight patients moderate asthma and eight patients severe asthma according to severity by NAEPP Expert Panel Report 2(1997). All subjects were free of recent upper respiratory tract infection within 2 weeks and showed positive methacholine challenge test ($PC_{20}$<16mg/ml). Methacholine provocation tests were performed twice on separate days allowing for an interval of one week. In the second test, pretreatment with the $M_2$ muscarinic receptor agonist pilocarpine($180{\mu}g$) through inhalation was performed be fore the routine procedures. Results : Eleven subjects with mild asthma and eight subjects with moderate asthma showed significant increase of $PC_{20}$ from 5.30$\pm$5.23mg/ml(mean$\pm$SD) to 20.82$\pm$22.56mg/ml(p=0.004) and from 2.79$\pm$1.51mg/ml to 4.67$\pm$3.53mg/ml(p=0.012) after pilocarpine inhalation, respectively. However, in the eight subjects with severe asthma significant increase of $PC_{20}$ from l.76$\pm$1.50mg/ml to 3.18$\pm$4.03mg/ml(p=0.161) after pilocarpine inhalation was not found. Conclusion : In subjects with mild and moderate asthma, function of $M_2$ muscarinic receptors was normal, but there was a dysfunction of these receptors in subjects with severe asthma. ηlese results suggest that function of $M_2$ muscarinic receptors is different according to severity of asthma.

• Journal of Acupuncture Research
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• v.17 no.4
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• pp.149-159
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• 2000

Bee-venom Acupucture has good effect on pain control but We may be anxious about the problem of side-effect. Bee-venom components are composed of phospholipase $A_2$, hyaluronidase, melitin, apamin, MCD peptide, citrate and so on. Especially Apamin, MCD peptide and histamine cause severe reacting that is named Anaphylaxis. Anaphylaxis is a clinical syndrome characterized by the acute system reaction of multiple organ systems to an IgE-mediated immunologic mediator release in previously sensitized individuals. Respiratory and dermatologic manifestations are the most commonly expressed clinical features of anaphylaxis, and a majority of anaphylactic reactions initially appear to be localized to these two systems. Anaphylatic reaction of bee-venom are expressed clinically ulticaria, itching sensation, erythema, dizziness, nausea, hypotension and so on. Especially ulticaria and erythema are end points of increased vascular permeability and vasodilatation at the other extreme of the clinical spectrum, Gastrointestinal mucosal edema and smooth muscle contraction can result in cramping abdominal pain, nausea, and vomiting. Therefore, we have observed anaphylatic reaction of bee-venom in 11 patients, who visited WonKwang University Kunpo Oriental Medical Center, treated bee venom. The results were summarized as follows : 1. The patient distribution ratio, in regard to sex, was shown to be 1 : 2.67 for male to females. In regard to age, it was shown that people in their 30's was the most predominant case, followed by people in their 20's, 30's, 50's and 60's, respectively. 2. When Anaphylaxis was occured, it was observed to abnormality of CBC, LFT, IgE, IgG. 3. In regard to patient condition, it was observed that fatigue was most frequent. 4. In regard to the number of times and quantity of bee venom inj., it was observed that anaphylaxis is most frequent at 7-10 times(1.6-2.0cc) 5. In regard to duration of reaction, it was observed that people in their l0min' was most frequent. In disappearing duration of anaphylaxic reaction, The results showed under 60min lcases(9%), 60-120min 7cases(64%) and 180-240min 3cases(27%). 6. In symptoms of anaphylaxis, The results showed hypotension 8cases(19%), itching sensation 7cases(16%), nausea 4cases(9%), erythema 4cases(9%) and dizziness 4cases(9%). In mentality, The results showed drowsy 8case(73%) and alert 3cases(27%). 7. Generally, patients were treated with Avil, Dexa IM and PDS, peniramine, cimetidine, Q-zyme per os after H/S, N/S inj. $O_2$ was supplied according to patient's symptom. In 1 severe case, Dopamine was iv injected.

• International Journal of Oral Biology
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• v.32 no.1
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• pp.13-22
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• 2007

The stem cell research is emerging as a cutting edge topic for a new treatment for many chronic diseases. Recently, dental stem cell would be possible for regeneration of tooth itself as well as periodontal tissue. However, the study of the cell characterization is scarce. Therefore, we performed the genetic profiling and the characterization of mouse fetus/neonate derived dental tissue and cell to find the identification during dental development. We separated dental arch from mandibles of 14.5 d fetal mice and neonate 0 d under the stereoscope, and isolated dental cells primarily from the tissues. Then, we examined morphology and the gene expression profiles of the primary cells and dental tissues from fetus/neonate and adult with RT-PCR. Primary dental cells showed heterogeneous but the majority was shown as fibroblast-like morphology. The change of population doubling time levels (PDLs) showed that the primary dental cells have growth potential and could be expanded under our culture conditions without reduction of growth rate. Immunocytochemical and flow cytometric analyses were performed to characterize the primary dental cell populations from both of fetus (E14.5) and neonate. Alpha smooth muscle actin (${\alpha}-SMA$), vimentin, and von Willebrand factor showed strong expression, but desmin positive cells were not detected in the primary dental cells. Most of the markers were not uniformly expressed, but found in subsets of cells, indicating that the primary dental cell population is heterogeneous, and characteristics of the populations were changed during culture period. And mesenchymal stem cell markers were highly expressed. Gene expression profile showed Wnt family and its related signaling molecules, growth factors, transcription factors and tooth specific molecules were expressed both fetal and neonatal tissue. The tooth specific genes (enamelin, amelogenin, and DSPP) only expressed in neonate and adult stage. These expression patterns appeared same as primary fetal and neonatal cells. In this study we isolated primary cells from whole mandible of fetal and neonatal mice. And we investigated the characteristics of the primary cells and the profile of gene expressions, which are involved in epithelial-mesenchymal interactions during tooth development. Taken together, the primary dental cells in early passages or fetal and neonatal mandibles could be useful stem cell resources.

• Journal of Life Science
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• v.19 no.5
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• pp.573-580
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• 2009

It has been previously reported that the carboxyl terminal residues 276 and 277 of ${\alpha}$-tropomyosin are important for actin affinity. In order to investigate actin affinities of these two residues of skeletal (HA) and smooth (QT) muscle ${\alpha}$-tropomyosins, a series of mutant tropomyosins were constructed in which residues at either 276 or 277 were individually replaced with a cysteine residue for chemical modification. These mutants were overexpressed in E. coli as unacetylated and Ala-Ser (AS) dipeptide fusion forms. While actin affinities of unacetylated tropomyosins were considerably low, those of AS/TMs were remarkably higher than those of corresponding unacetylated tropomyosins. However, actin affinities of AS/TM24 (QC) and AS/TM29 (HC) were dramatically lower than those of other AS/TMs and were close to those of unacetylated tropomyosins. In addition, actin affinities of unacetylated TM24 (QC) and TM29 (HC) failed to be restored in the presence of troponin, unlike unacetylated TM10 (HA) and TM23 (CA). These results indicated that the presence of a cysteine residue at 277 caused a drastic decrease in actin affinity, and also that the residue 277 is important for actin affinity of ${\alpha}$-tropomyosin. Since TM23 (CA) showed high actin affinity, it may serve as a valuable tool for chemical modification studies for investigating the interaction of the carboxyl terminal residues of ${\alpha}$-tropomyosin with actin and/or troponin.