• Proceedings of the PSK Conference
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• 2002.10a
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• pp.250.2-251
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• 2002

DA-8159 is a new. highly selective. potent cyclic-GMP phosphodiesterase 5 inhibitor developed by Dong-A Pharmaceutical Company(Kyunggi, Korea) as an oral drug for the treatment of erectile dysfunction. NO- cGMP signal transduction pathway plays a key role for relaxation of corpus cavernosal smooth muscle. In this study. the efficacy of DA-8159 was evaluated by measuring the length of uncovered penile mucosa in spinal cord injury(SCI) rabbits. (omitted)

• Journal of Physiology & Pathology in Korean Medicine
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• v.27 no.4
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• pp.400-408
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• 2013

This study aimed to investigate the relaxation effects and its underlying mechanisms of Rubus coreanus(RC) extract in contracted rabbit corpus cavernous tissues by phenylephrine(PE) $1{\mu}M$. In order to define the relaxation effects of RC, rabbit corpus cavernous tissues were prepared in $2{\times}2{\times}6mm$ sized strip. The dose-dependent relaxation responses of RC at 0.01-3.0 $mg/m{\ell}$ in contracted strips induced by PE were measured and also observed after endothelial denudation. To analyze the underlying mechanisms of RC-induced relaxation, indomethacin(IM), tetraethylammonium chloride(TEA), $N{\omega}$-nitro-L-arginine (L-NNA), methylene blue(MB) were treated before RC extract infused into precontracted strips induced by PE. To study the effect of RC extract on influx of extracellular $Ca^{2+}$ in corpus cavernous strips, calcium chloride(Ca) 1 mM infused into precontracted strips induced by PE after pretreatment of RC extract in $Ca^{2+}$-free krebs-ringer solution. To investigate cytotoxic activity and nitric oxide(NO) concentration of RC extract on human umbilical vein endothelial cell(HUVEC), cell viability on HUVEC was measured by MTT assay, and NO concentration was measured by Griess reagent system. The cavernous strips were significantly relaxed by RC extract at 1.0 $mg/m{\ell}$, 3.0 $mg/m{\ell}$ and the relaxation responses to RC were inhibited significantly by endothelial disruption. The pretreatment of IM, TEA didn't affect RC extract-induced endothelium-dependent relaxation, but the pretreatment of L-NNA, MB reduced RC extract-induced endothelium-dependent relaxation. When $Ca^{2+}$ was supplied the cavernous strips which were precontracted by PE in a $Ca^{2+}$-free krebs-ringer solution, contraction of strips was increased, but pretreatment of RC inhibited contractile response to $Ca^{2+}$. When RC extract was applicated on HUVEC, NO concentration was increased. Our findings show that RC extract exerts a relaxing effect on corpus cavernosum in part by suppressing influx of extracellular $Ca^{2+}$ through activating the NO-cGMP system.

• Journal of Yeungnam Medical Science
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• v.23 no.1
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• pp.52-61
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• 2006

Background: Korean ginseng (KG) has been used as a general tonic, and for voiding dysfunction for a long time in oriental society. However, scientific basic studies on the use of KG, have been rare, especially for voiding and erectile dysfunction. This study was performed to investigate the effects of KG on voiding and erectile function by examining the effects of total saponin (TS) on the bladder, urethral and penile cavernosal smooth muscle. Materials and methods: To examine the effects of TS, NewZeland white rabbits were used to obtain tissue strips from the smooth muscle of the bladder, proximal urethra and corpus cavernosum. Adult Sprague Dawley rats were used to examine the changes in urodynamic findings and penile erection after administration of TS. Results: In proximal urethral strips, the rate of relaxation of the proximal urethra was increased from $9.0{\pm}2.9$ to $33.7{\pm}4.8%$ in a dose-dependent manner when the concentration of TS was added accumulatively from 0.25 mg/ml to 4.0 mg/ml (p<0.05). However, no significant response was observed in the bladder strips within these concentration ranges. For the corpus cavernosal strips, the rate of relaxation ranged from $5.8{\pm}2.1$ to $36.7{\pm}5.8%$, increasing in a dose-dependent manner when TS was increased from 1.0 mg/ml to 4.0 mg/ml (p<0.05). After administration of 0.1 ml of TS (32 mg/ml) in the rat, the bladder pressure was $37.5{\pm}8.5$ mmHg at $52.1{\pm}7.0$ sec. during isovolumetric bladder contraction, showing no significant differences from $35.7{\pm}7.8mmHg$ and $50.7{\pm}7.2$ sec, respectively, before treatment. However, when 0.1 ml of TS (32 mg/ml) was administered, the relative reduction of urethral pressure was $6.9{\pm}0.5mmHg$ at $62{\pm}7.5$ sec, which was significantly higher compared to $4.6{\pm}1.1mmHg$ at $45{\pm}10$ sec before treatment (p<0.05). For the cavernosal injection study, the change in intracavernosal pressure (${\Delta}ICP$) was examined after administering 0.1 ml of TS. The cumulative additions of TS at concentrations from 0.5 mg/ml to 32 mg/ml increased ${\Delta}ICP$ from $1.3{\pm}0.5$ to $21.3{\pm}7.8mmHg$ in a dose-dependent manner (p<0.05). The duration of tumescence was from $0.3{\pm}0.1$ to $5.2{\pm}0.2$ min, showing dose-dependent increase (p<0.05). Furthermore, the cumulative addition of TS at concentrations from 0.5 mg/ml upto 32 mg/ml did not cause any significant change in systemic blood pressure. Conclusion: These results suggest that ginseng improves voiding functions, which is mainly achieved by TS relaxing the proximal urethra, the most important part of the bladder outlet function. In addition, ginseng safely induced a penile erection hemodynamically by relaxing the corpus cavernosum.

• Archives of Pharmacal Research
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• v.25 no.6
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• pp.873-878
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• 2002

OA-8159, a new Phosphodiesterase (PDE) 5 inhibitor, has exhibited potent erectogenic potential in a penile erection test in rats and anesthetized dogs. In this study, we investigated the mechanism of its erectogenic activity by measuring the activity of OA-8159 against a various PDE isozymes and assessing cGMP and cAMP formation in a rabbit corpus cavernosum in vitro. DA-8159 inhibited the PDE 5 activity in rabbit and human platelets, which the $IC_{50}$ was 5.84$\pm$1.70 nM and 8.25$\pm$2.90 nM, respectively. The $IC_{50}$ of DA-8159 on PDE 1, PDE2, PDE 3 and PDE 6 were 870$\pm$57.4 nM, $101\pm$5 $\mu$M, 52.0$\pm$3.53 $\mu$M and 53.3$\pm$2.47 nM, respectively. This suggests that DA-8159 is a potent, highly selective, competitive inhibitor of PDE 5-catalyzed cGMP hydrolysis. The rates of cGMP hydrolysis catalyzed by human platelets-derived PDE 5 as a function of the cGMP concentration (5~100 nM) and two-fixed DA-8159 concentration (11.3 and 18.8 nM) were investigated in order to characterize the mode of PDE 5 inhibition by DA-8159. DA-8159 increased the apparent 4K_{m}$ value for cGMP hydrolysis but had no effect on the apparent $V_{max}$, indicating a competitive mode of inhibition. DA-8159 increased the cGMP concentrations in the rabbit corpus cavernosum dose dependently. In the presence of sodium nitroprusside (SNP), DA-8159 significantly sti\mulated the accu\mulation of cGMP when compared to the control level. This indicated that the enhancement of a penile erection by DA-8159 involved the relaxation of the cavernosal smooth \muscle by NO-sti\mulated cGMP accu\mulation. In conclusion, DA-8159 is a selective inhibitor of PDE 5-catalyzed cGMP hydrolysis and the enhancement of a penile erection by DA-8159 is mediated by the relaxation of the cavernosal smooth \muscle by the NO-sti\mulated cGMP accu\mulation.

• The Korean Journal of Physiology
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• v.29 no.1
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• pp.61-67
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• 1995

The extract of Ginkgo bibloba (EGb) is a complex mixture of natural products from the Ginkgo leaves and clinically used for the treatment of cerebral and peripheral circulatory disturbances due to its combined activity of several vasoactive principles. In this study we investigated the action of EGb and its mechanism in isolated rabbit corporal smooth muscle to evaluate the possibility of using this material as a pharmacoerecting agent. Strips of rabbit corpus cavernosum were mounted in organ chambers to measure isometric tension. EGb began to exert an relaxing effect at 1 mg/ml in the submaximally precontracted muscle strips with phenylephrine $(PHE,\;5{\times}10^{-6}\;M)$; causing concentration-dependent relaxation with maximal effect at $3{\sim}5\;mg/ml$. That relaxation was partially inhibited by removal of the smooth muscle endothelium or by pretreatment with a NO scavenger, pyrogallol $(10^{-4}\;M)$ or the guanylate cyclase inhibitor, methylene blue $(10^{-4}\;M)$. Pretreatment with EGb (3 mg/ml) inhibited PHE- $(5{\times}10^{-6}\;M)$ or KCI- (20 and 40 mM) induced contraction of muscle strip. In calcium-free high potassium solution EGb depressed the basal tone of the depolarized muscle strip and inhibited calcium-induced contraction when $CaCl_2$ $(10^{-4}\;M)$ was added. These results suggest that EGb relaxes rabbit corpus cavernosal smooth muscle through multiple action mechanisms that include increasing the release of nitric oxide from the corporal sinusoidal endothelium, sequestration of intracytosolic calcium, and maybe a hyperpolarizing action.