• Proceedings of the Korean Society of Applied Pharmacology
• /
• 1994.04a
• /
• pp.288-288
• /
• 1994

1.목적 $K^{+}$ 통로 개방제인 cromakalim과 levcromakalim이 원형질막의 $K^{+}$ 통로를 개방시켜 막의 과분극을 일으킴으로서 강력한 혈관 이완작용을 일으킨다는 것은 주지하는 바다. 본 연구진들은 지난 2년간의 신약개발 연구사업을 통하여 cromakalim과 pinacidil 등 여러종의 K+통로개방제가 건전한 평활근 세포에서 phenylephrine뿐만 아니라 saponin처리에 의한 투과성 근세포 (permeabilized cells)에서 inositol 1,4,5-triphosphate (IP$_3$)에 의한 수축도 억제함을 보고 하였다. 본 연구에서는 이러한 수축작용에 대한 SPEX fluolog-2 spectrophotometer를 사용하여 돼지의 관상동맥 혈관근의 세포질내 $Ca^{++}$의 농도 ([$Ca^{++}$])의 변동을 관찰하였다. 정상 관상동맥 혈관근 조직에서 acetylcholine (0.1-1$\mu$M)에 의한 [Ca$^{++}$]농도의 증가와 b-escin 처리에 의한 skinned strip에서의 IP3 (1-5$\mu$M)에 의한 [Ca$^{2+}$]의 증가는 cromakalim과 levcromakalim의 전처치에 의하여 현저히 억제되었다. Skinned strip에서 이러한 K+ 통로 개방제에 의한 $IP_3$-요도 ($Ca^{2+}$)i 증가의 억제가 apamin (1-5 mM)과 glibenclamide (1$\mu$M)에 의하여 봉쇄되었으나, chrybdotoxin (0.1$\mu$M)에 의하여는 영향을 받지 아니하였다 한편 skinned strip에서 cromakalim은 GTP${\gamma}$s에 의한 [$Ca^{2+}$]i의 증가는 봉쇄하였으나 caffeine에 의한 [$Ca^{2+}$]i의 증가는 영향을 미치지 아니하였다. 이러한 연구결과로 보아 cromakalim과 levcromakalim과 같은 $K^{+}$ 통로 개방제가 세포막의 $K^{+}$ 통로를 개방하는 작용 뿐만 아니라 적어도 sarcoplasmic membrane에서 $Ca^{2+}$의 유리를 봉쇄함으로써 강력한 혈관 평활근 이완 작용을 나타내는 것으로 시사된다.

• The Korean Journal of Physiology and Pharmacology
• /
• v.1 no.6
• /
• pp.759-767
• /
• 1997

In the present study, we characterized the non-vascular smooth muscle relaxant effects of a novel benzoyran derivative ,SKP-450 (2-[2'(1',3'-dioxolone)-2-methyl-4- (2'-oxo-1'-pyrrolidinyl) -6-nitro-2H-1- benzopyran) and its metabolite, SKP-310, in comparison with levcromakalim (LCRK). In the rat stomach fundus, the spontaneous motility stimulated by $10^{-6.5}\;M$ bethanechol was completely eliminated not only by $10^{-7}\;M$ SKP-450 but also by $10^{-6}\;M$ LCRK, which were blocked by $10^{-6}\;M$ glibenclamide. The inhibitory effect of SKP-450 $pD_2,\;3.94{\pm}0.66)$ was much less than LCRK $(pD2,\;5.73{\pm}0.38,\;p<0.05)$. In the bethanechol $(10{-6.5 }\;M)-stimulated$ urinary bladder, the tonus was decreased in association with elimination of spontaneous motility by $10^{-7}\;M$ M SKP-450 and $10^{-6}\;M\;LCRK\;(pD2,\;6.77{\pm}0.06)\;(P<0.05)$, which were inhibitable by $10^{-6}\;M$ glibenclamide. The inhibitory effect of SKP-450 $(pD2,\;7.66{\pm}0.05)$ was significantly more potent than that of LCRK $(pD2,\;6.77{\pm}0.06,\;p<0.05)$. In the rat uterus stimulated by $PGF_{2\alpha}\;(10^{-7}\;M)$, both increased tonus and spontaneous motility were eliminated by $10^{-6}\;M$ LCRK with slight depression of the tonus, but not by SKP-450 $(10^{-5}\;M)$. The stimulated trachea of guinea-pig by $10^{-6.5}\;M$ bethanechol was moderately suppressed by SKP-450 $(10^{-6}{sim}10^{-5}\;M)$ but little by SKP-310. In association with the relaxant effects, SKP-450 $(10^{-6}\;M)$ and LCRK $(10^{-5}\;M)$ caused a significant stimulation of the $^{86}Rb$ efflux from rat urinary bladder and stomach fundus, which were antagonized by $10^{-5}\;M$ glibenclamide, whereas the $K^+$ channel openers could not exert a stimulation of the $^{86}Rb$ efflux from rat uterus. In conclusion, it is suggested that SKP-450 exerts potent relaxant effects on the urinary bladder detrusor muscle and duodenum, whereas it shows much less effect on stomach fundus and uterus as contrasted to LCRK.

• The Korean Journal of Physiology and Pharmacology
• /
• v.1 no.1
• /
• pp.27-34
• /
• 1997

In the present study, it was aimed to further indentify the intracellular action mechansm of cromakalim and levcromakalim in the porcine coronary artery. In intact porcine coronary arterial strips loaded with fura-2/AM, acetylcholine caused an increase in intracellular free $Ca^{2+}$ $([Ca^{2+}]_i)$ in association with a contraction in a concentration-dependent manner. Cromakalim (1 ${\mu}M$) caused a reduction in acetylcholine-induced increased $[Ca^{2+}]_i$ not only in the mormal physiological salt solution (PSS) but also in $Ca^{2+}$-free PSS (containing 1 mM EGTA). In the skinned strips prepared by exposure of tissue to 20 .${\mu}M$ B-escin, inositol 1,4,5-trisphosphate ($IP_3$) evoked an increase in $[Ca^{2+}]_i$, but it was without effect on the intact strips. The $IP_3$-induced increase in $[Ca^{2+}]_i$ was inhibited by cromakalim by 78% and levcromakalim by 59% (1 .${\mu}M$, each). Pretreatment with glibenclamide (a blocker of ATP-sensitive $K^+$ channels, 10 .${\mu}M$) and apamin (a blocker of small conductance $Ca^{2+}$-activated $K^+$ channels, 1 .${\mu}M$) strongly blocked the effect of cromakalim and levcromakalim. However, charybdotoxin (a blocker of large conductance $Ca^{2+}$-activated $K^+$ channels, 1 .${\mu}M$) was without effect. In addition, cromakalim inhibited the $GTP{\gamma}S$ (100 .${\mu}M$, non-hydrolysable analogue of GTP)-induced increase in $[Ca^{2+}]_i$. Based on these results, it is suggested that cromakalim and levcromakalim exert a potent vasorelaxation, in part, by acting on the $K^+$ channels of the intracellular sites (e.g., sarcoplasmic reticulum membrane), thereby, resulting in decrease in release of $Ca^{2+}$ from the intracellular storage site.