• Analytical Science and Technology
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• v.21 no.5
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• pp.412-423
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• 2008

A procedure based on solid-phase extraction (SPE) followed by liquid chromatography-tandem mass spectrometry has been developed for the simultaneous analysis of 55 basic drugs in equine urine. The test scope covers diversified classes of drugs including some ${\beta}$-blockers, ${\beta}$-agonists, antihypotensives, CNS stimulants, sedatives, tranquilizers, antidepressants, antihypertensives and so on. LC-MS/MS separation and quantification was carried out in positive electrospray ionization and multiple reaction monitoring (MRM) mode. Four different brands of mixed mode cation exchange SPE sorbents; UCT XTRACT$^{(R)}$ XRDAH, Supelco DSC-MCAX$^{(R)}$, Varian Bond Elut Certify$^{(R)}$ and Waters Oasis$^{(R)}$ MCX were compared. The UCT XTRACT$^{(R)}$ XRDAH sorbent provided the best results in the preconcentration of samples, yielding relative recoveries higher than 80% except for terbutaline (41.3%), salbutamol (71.5%), heptaminol (70.7%), phenylpropanolamine (66.3%). Detection limits of the target drugs provided by the proposed analytical procedure were between 0.2~8.3 ng/mL.

• Korean Journal of Veterinary Research
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• v.36 no.1
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• pp.83-91
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• 1996

Activation of $K^+$ channels induces relaxation of smooth muscles by reducing electrical excitability and cytosolic free $Ca^{2+}$ level. ${\beta}$-adrenergic agonist isoproterenol is known to induce relaxation of the uterine smooth muscle by membrane hyperpolarization and $K^+$ efflux. Recently it is suggested that the activity of $Ca^{2+}$-activated $K^+$ channel was increased by isoproterenol in the uterine myocytes isolated from myometrium of the pregnant rat. However, the type of $K^+$ channel mediating the relaxant effect of isopreterenol in the tissue level has not yet studied. In this work, we investigated the type of $K^+$ channels involved in the isoproterenol-induced relaxation of uterine smooth muscle by measuring the integrated insometric tension of the estrogen-treated isolated nonpregnant rat uterus. Contraction of uterine tissue was induced by oxytocin (0.2nM, 2~3 contractions/min) or high KCl(20~80mM). The result are as follows : 1. Isoproterenol($10^{-10}{\sim}10^{-4}M$) inhibited oxytocin-induced contraction of isolated rat uterus($EC_{50}=1.17{\times}10^{-10}M$). 2. Isoproterenol($10^{-10}{\sim}10^{-4}M$) effectively inhibited uterine contraction induced by low KCl(20~40mM) but little those induced by high KCl(60~80mM). 3. Relaxant effect of isoproterenol($10^{-10}{\sim}10^{-4}M$) on 0.2nM oxytocin-induced contraction was effectively reduced by 4-aminopyridine(3, 10mM) but little by TEA(10~30mM), $Ba^{2+}$($1{\sim}30{\mu}M$) and glibenclamide($100{\mu}M$). Our data suggest that the relaxant effect of isoproterenol is mediated by the $K^+$ channel(s) which can be blocked by 4-aminopyridine.

• Journal of Chest Surgery
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• v.40 no.6 s.275
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• pp.407-413
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• 2007

Background: The brain natriuretic peptide (BNP) level has been reported in some studies to be associated with the occurrence of atrial fbrillation (AF). The aim of this study is to evaluate the potential usefulness of the BNP level as a predictor of the occurrence of postoperative (postop) AF and to assess the relationship of the BNP level with the onset of AF and the restoration of sinus rhythm. Material and Method: From January 1, 2005 to February 28, 2006, 82 patients without a history of atrial arrhythmia that had undergone cardiac surgery were enrolled in the study. Blood samples for plasma BNP were drawn daily for all these patients from the preoperative (preop) day to the 7th postop day. The patient records were reviewed and postop EKGs were checked daily for AF until the time of discharge. Result: Patients were divided into two groups based on development of postop AF. Postoperative AF developed in 26 patients (31.7%). There was no significant statistical difference in age, sex distribution, preop left ventricle ejection fraction, hypertension, left ventricular hypertrophy, or the use of beta blockers between the non-postop AF and postop AF group. More patients in the AF group had undergone valve surgery (39.3% versus 76.9%, p=0.002). The preop left atrium size was significantly larger in the AF patients ($43.8{\pm}10.3 mm$ versus $49.8{\pm}11.5 mm$, p=0.029). The preop plasma BNP levels were higher in the postop AF patients ($144.1{\pm}20.8 pg/mL$ versus $267.5{\pm}68 pg/mL$, p=0.034). In the postop AF group, the plasma BNP level was the highest on the 3rd postop day. Postop AF developed in most patients by the 3rd postop day; restored sinus rhythm developed by the 7th postop day. Conclusion: Elevated plasma BNP levels may lead to the occurrence of postop AF in patients undergoing cardiac surgery. Patients who have a high risk of postop AF should be considered for aggressive prophylactic antiarrhythmic therapy.