• Proceedings of the Korean Society of Applied Pharmacology
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• 1992.05a
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• pp.36-36
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• 1992

기니픽심장에서 유두근을 적출하여 valve 쪽은 silver wire에 연결하여 수축력을 측정하고 mural end는 sylgard floor에 pin으로 고정하여 1Hz로 자극하였다. 이때 사용된 영양액은 Tyrode Ringer로 bath내 은도는 36$^{\circ}C$이고 97% 0$_2$, 3% $CO_2$로 포화시켜 사용하였다. 수축력이 일정해진 후 막전위는 conventional electrode를 이용해서 기록하고, 세포내 $Na^{＋}$ 이온 활성도( $a_{Na}$ $^{i}$ )는 $Na^{＋}$ 선택적 전극을 이용해서 기록하였다. 적출 기니픽 심근에서 pinacidil, cromakalim, RP49356 둥의 $K^{＋}$ channel opener는 활동전위 기간(APD)과 수축력 감소을 일으켰고, pinacidil과 cromakalim에 의한 APD 감소는 glibenclamide (10 $\mu$M)에 의해 거의 억제되었다. Pinacidil, RP49356 및 cromakalim에 의한 수축력 감소시 세포내 $Na^{＋}$ 이온농도( $a_{Na}$ $^{i}$ )의 감소가 나타났으며 glibenclamide(10 $\mu$M)에 의한 APD의 감소는 거의 차단되었으나 $a_{Na}$ $^{i}$ 감소는 일부 나타났으며 이때 수축력의 감소도 나타났다.

• The Korean Journal of Pharmacology
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• v.30 no.2
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• pp.191-203
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• 1994

$K^+$ channel openers (KCOs) are known to have a wide range of effects by opening the $K^+$ channel in plasma membranes of various smooth muscles, cardiac muscle and pancreatic ${\beta}-cell$. In the present study, we investigated the effects of 5 types of KCOs, cromakalim, RP49356, pinacidil, nicorandil and diazoxide on the contractility of isolated rat uterus. All KCOs tested inhibited the uterine contraction induced by 0.2 nM oxytocin in a dose-dependent manner. Individual KCO and its $pD_2$ values were cromakalim 6.5, RP49356 6.3, pinacidil 5.92, nicorandil 4.43 and diazoxide 4.18. The relaxant effects of KCO were inhibited by glibenclamide (0.3, 1 and $10\;{\mu}M$) with $pA_2$ values of cromakalim 6.91, RP49356 6.59, pinacidil 6.55, nicorandil 5.97 and diazoxide 6.37. In addition, the relaxant effect of cromakalim or pinacidil was antagonised by TEA, a non-selective $K^+$ channel blocker, but not by apamin. Contractions induced by low concentration of KCI (< 40 mM) were inhibited by cromakalim $(100{\mu}M)$ and nicorandil $(300{\mu}M)$, but those evoked by higher concentration (> 40 mM) of KCI were little affected. In ovariectomized rat uterus, cromakalim dose-dependently inhibited oxytocin-induced contraction and glibenclamide $(10{\mu}M)$ inhibited the relaxant effect of cromakalim with $pD_2$ and $K_B$ values of 7.48 and $1.26{\times}10^{-7}M$, respectively. In estrogen-primed rat uterus, these values were 6.51 and $1.57{\times}10^{-7}M$, respectively, indicating that the cromakalim is less effective on the estrogen-treated uterine smooth muscle. Our results suggest that the KCO-sensitive $K^+$ channels participate in the motility of uterine smooth muscle and such channels are, at least in part, under the control of estrogen. In addition, our data Indicate that the type of $K^+$ channels activated by KCO is ATP-sensitive $K^+$ channels which is blocked by glibenclamide.

• The Korean Journal of Pharmacology
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• v.28 no.2
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• pp.147-162
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• 1992

The objectives of the present experiments were to characterize the effects of the peptides belonging to the pancreatic polypeptide family on the contractility of cerebral arteries and to observe the interactions of these peptides with the cyclic nucleotide activators and the potassium channel openers. Dogs of either sex, $20{\sim}30\;Kg$ in weight, were sacrificed. Basilar and middle cerebral arteries from brain were isolated and prepared for myography in the PSS equilibrated with 95% $O_2$ and 5% $CO_2$ at $37^{\circ}C$. The endothelial cells of the spiral strips were removed by CHAPS solution (0.3% w/v, 15 seconds). 1. PP, PYY and NPY contracted the arterial strips concentration-dependently with a rank order of potency of PYY>NPY>PP. These peptides were 20 to 200 times more potent than norepinephrine, and only PYY showed a greater potency than 5-HT. 2. Cyclic nucleotide activators, forskolin (for cAMP) and sodium nitroprusside (for cGMP) reduced the basal tone and inhibited the PP-, PYY- and NPY- induced contractions by concentration-dependent manners. Forskolin was more potent in reducing basal tone than sodium nitroprusside. 3. Potassium channel openers, RP 49356, P 1060 and BRL 38227 reduced the basal tone concentration-dependently and tended to inhibit the PP-, PYY- and NPY- induced contractions. Notably, BRL 38227 with low concentration $(0.1\;{\mu}M)$ enhanced the contractions induced by those peptides while P 1060 inhibited the contractions concentration-dependently. 4. The combinations of the cyclic nucleotide activators and the potassium channel openers were slightly additive in reducing the basal tone. P 1060 and BRL 38227 enhanced the relaxant effect of sodium nitroprusside significantly. On the PYY-induced contration $(0.1\;{\mu}M)$, $K^+$ channel openers tended to inhibit the inhibitory actions of forskolin and sodium nitroprusside. P 1060 and BRL 38227 antagonized the inhibitory action of sodium nitroprusside significantly. The results of the present study may be summarized that in canine cerebral arteries, not only NPY but also PYY may play a role in a cerebrovascular spasm, and intracellular concentration of either cAMP or cGMP may be involved in the mechanism of vasoconstrictive actions of these peptides, which may be affected either positively or negatively by a $K^+$ channel opener.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1993.04a
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• pp.160-160
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• 1993

목적: Guinea pig heart의 ATP sensitive $K^{＋}$ channel xenopus oocyte에 발현시켜 연구하고져 본 실험을 행하였다. 실험방법: 기니픽 심장으로부터 ,RNA를 분리하여 50ng/$\mu$l의 농도로 50nl를 xenopusdp 주입하였다. Xenpus oocyte에서 conventional electrode를 이용 막전휘를 측정하였고, pH selective 미세전극으로 세포내 pH를 측정하였다. 막전위에 미치는 potassium channel opener, blocker, KCN의 작용을 관찰하였다. 결과: 기니픽 심장 mRNA를 주입하거나 주입하지 않은 xenopus oocyte에서 $K^{＋}$channel opener인 cromakalin, RP49356등은 과분극을 일으키지 못하였다. 그러나 세포내 ATP 감소제인 KCN은 농도 의존적으로 과분극을 일으켰으나 ,glibenclamide에 의해 차단되는 않았다. mRNA를 주입한 oocyte에서 Na-H 자극제인 NH$_4$Cl은 pH 변동을 일으켜 NA-H exchange를 expression 시켰다. 결론: Xenopus oocyte는 cromakalin등에 의해 open되는 $K^{＋}$channel 은 없었고, 기니픽 심근의 ATP sensitive $K^{＋}$channel로 expression 되지 않았으나 Na-H exchange 는 expression 됨을 알 수 있었다. KCN으로 open 되는 $K^{＋}$channel이 있었으나 glibenclamide에는 차단되지 않는 channel이였다.