Effects of Extracellular $Ca^{2+}$ and $Ca^{2+}$-Antagonists on Endothelium-Dependent Relaxation in Rabbit Aorta

서석효,구용숙,박춘옥,황상익,김기환,Suh, Suk-Hyo,Goo, Yong-Sook,Park, Choon-Ok,Hwang, Sang-Ik,Kim, Ki-Whan The Korean Physiological Society 1990 대한생리학회지 Vol.24 No.1

토끼 흉부 대동맥을 이용하여 내피세포 의존성 혈관이완에 대한 세포외 $Ca^{2+}$과 여러가지 $Ca^{2+}$ 길항제의 효과를 분석하여 EDRF의 작용기전을 밝혀 보고자 하였다. 대동맥 횡단 절편의 등장성 수축은 $10^{-7}\;M$ 노에피네프린으로 유발시켰으며, $10^{-6}\;M$ 사세틸콜린으로 내피세포 의존성 혈관이완을 일으켰다. 내피세포는 작은 솜뭉치로 부드럽게 문질러서 제거하였으며, hemolysate를 사용하여 EDRF에 대한 헤모글로빈의 효과를 관찰하였다. 결과를 종합하면 다음과 같다. 1) 아세틸콜린에 의한 내피세포 의존성 혈관이완은 두 시기, 즉 초기급속이완기와 후기완만이완기로 나타났다. 2) 세포외 $Ca^{2+}$을 낮추면, 아세틸콜린에 의한 내피세포 의존성 혈관이완이 감소하였으며, 특히 후기완만이완기가 감소하였다. 3) Verapamil, nifedipine, $Mn^{2+}$ 및 $Cd^{2+}$은 내피세포 의존성 혈관이완에 영향이 없었던 반면 $La^{3+}$와 $Co^{2+}$는 억제시켰다. 4) 헤모글로빈을 투여하면 내피세포가 없는 절편에서는 기초긴장도의 변화가 없었으나 내피세포가 있는 절편에서는 기초긴장도가 증가하였고 아세틸콜린에 의한 내피세포 의존성 혈관이완도 완전히 억제되었다. 이상의 결과로부터 세포외 $Ca^{2+}$은 주로 후기완만이완기에 작용하며 이때 사용되는 $Ca^{2+}$ 유입 통로는 $Ca^{2+}$ 길항제로 억제되지 않는 것으로 결론지을 수 있다. The effects of extracellular $Ca^{2+}$ and various $Ca^{2+}$ antagonists on endothelium-dependent relaxation to acetylcholine were studied in the isolated rabbit thoracic aorta in order to elucidate the control mechanism of endothelium derived relaxing factor (EDRF) release. Endothelium was removed from aortic strips by gentle rubbing with cotton ball. The effect of hemoglobin on basal tension was also observed with hemolysate. The results obtained were as follows: 1) Endothelium-dependent relaxation (EDR) to acetylcholine (ACh) showed biphasic pattern; the initial rapid relaxation phase and the late slow relaxation phase. 2) With the depletion of the extracellular $Ca^{2+}$, EDR was gradually suppressed, especially the late slow relaxation. 3) Verapamil, nifedipine, $Mn^{2+}$ and $Cd^{2+}$ had not any effect on EDR, while $La^{3+}$ and $Co^{2+}$ suppressed EDR completely. 4) The resting tension of the strips with rubbed endothelium was not altered by the addition of hemoglobin. That of the strips with intact endothelium, however, was enhanced and EDR to ACh was completely blocked From these results, we suggest that extracellular $Ca^{2+}$ is necessary for ACh-induced slow relaxation while $Ca^{2+}$ antagonists have not any effect on EDR.

토끼 대동맥 평활근의 내피세포 의존성 이완에 미치는 Ca²⁺ 및 Ca²⁺ 길항제의 효과

서석효(Suh, Suk-Hyo),구용숙(Goo, Yong-Sook),박춘옥(Park, Choon-Ok),황상익(Hwang, Sang-Ik),김기환(Kim, Ki-Whan) 대한생리학회 1990 대한생리학회지 Vol.24 No.1

토끼 흉부 대동맥을 이용하여 내피세포 의존성 혈관이완에 대한 세포외 Ca²⁺과 여러가지 Ca²⁺ 길항제의 효과를 분석하여 EDRF의 작용기전을 밝혀 보고자 하였다. 대동맥 횡단 절편의 등장성 수축은 10^-7 M 노에피네프린으로 유발시켰으며, 10^-6 M 사세틸콜린으로 내피세포 의존성 혈관이완을 일으켰다. 내피세포는 작은 솜뭉치로 부드럽게 문질러서 제거하였으며, hemolysate를 사용하여 EDRF에 대한 헤모글로빈의 효과를 관찰하였다. 결과를 종합하면 다음과 같다. 1) 아세틸콜린에 의한 내피세포 의존성 혈관이완은 두 시기, 즉 초기급속이완기와 후기완만이완기로 나타났다. 2) 세포외 Ca²⁺을 낮추면, 아세틸콜린에 의한 내피세포 의존성 혈관이완이 감소하였으며, 특히 후기완만이완기가 감소하였다. 3) Verapamil, nifedipine, Mn²⁺ 및 Cd²⁺은 내피세포 의존성 혈관이완에 영향이 없었던 반면 La³⁺와 Co²⁺는 억제시켰다. 4) 헤모글로빈을 투여하면 내피세포가 없는 절편에서는 기초긴장도의 변화가 없었으나 내피세포가 있는 절편에서는 기초긴장도가 증가하였고 아세틸콜린에 의한 내피세포 의존성 혈관이완도 완전히 억제되었다. 이상의 결과로부터 세포외 Ca²⁺은 주로 후기완만이완기에 작용하며 이때 사용되는 Ca²⁺ 유입 통로는 Ca²⁺ 길항제로 억제되지 않는 것으로 결론지을 수 있다. The effects of extracellular Ca²⁺ and various Ca²⁺ antagonists on endothelium-dependent relaxation to acetylcholine were studied in the isolated rabbit thoracic aorta in order to elucidate the control mechanism of endothelium derived relaxing factor (EDRF) release. Endothelium was removed from aortic strips by gentle rubbing with cotton ball. The effect of hemoglobin on basal tension was also observed with hemolysate. The results obtained were as follows: 1) Endothelium-dependent relaxation (EDR) to acetylcholine (ACh) showed biphasic pattern; the initial rapid relaxation phase and the late slow relaxation phase. 2) With the depletion of the extracellular Ca²⁺, EDR was gradually suppressed, especially the late slow relaxation. 3) Verapamil, nifedipine, Mn²⁺ and Cd²⁺ had not any effect on EDR, while La³⁺ and Co²⁺ suppressed EDR completely. 4) The resting tension of the strips with rubbed endothelium was not altered by the addition of hemoglobin. That of the strips with intact endothelium, however, was enhanced and EDR to ACh was completely blocked From these results, we suggest that extracellular Ca²⁺ is necessary for ACh-induced slow relaxation while Ca²⁺ antagonists have not any effect on EDR.

Effects of Electrolytes and Drugs on the Inhibitory Junction Potentials Recorded from the Antrum of Guinea-pig Stomach

구용숙,서석효,이석호,황상익,김기환,Goo, Yong-Sook,Suh, Suk-Hyo,Lee, Suk-Ho,Hwang, Sang-Ik,Kim, Ki-Whan The Korean Physiological Society 1990 대한생리학회지 Vol.24 No.1

The effects of electrolytes, adenosine, ATP, 5-hydroxytryptamine (5-HT, serotonin) and ketanserin on the inhibitory junction potentials (IJPs) were investigated to clarify the interactions of these drugs with the neurotransmitters released from non-adrenergic, non-cholinergic nerves in the antrum of guinea-pig stomach. Electrical responses of antral circular muscle cells were recorded intracellularly using glass capillary microelectrode filled with 3 M KCI. All experiments were performed in Tris-buffered Tyrode soluition which was aerated with 100% $O_{2}$ and kept at $35^{\circ}C$. The results obtained were as follows: 1) Inhibitory junction potential (IJP) was recorded in antral strip, while excitatory junction potential (EJP) was recorded in fundic strip. 2) IJP recorded in antral strip was not influenced by atropine $(10^{-6}\;M)$ and guanethidine $(5{\times}10^{-6})$. 3) The amplitude of IJP increased in high $Ca^{2+}$ solution, while that of IJP decreased in high $Mg^{2+}$ solution or by $Ca^{2+}$ antagonist (verapamil). Apamin, $Ca^{2+}$-activated $K^{+}$ channel blocker blocked IJP completely. 4) ATP and adenosine decreased the amplitude of IJP. 5) 5-HT decreased the amplitude of IJP with no change of the amplitude of slow waves, while ketanserin (5-HT type 2 blocker) decreased the amplitude of slow waves markedly with no change in that of IJP. From the above results, the following conclusions could be made. 1) IJP recorded in antral strip is resulted from neurotransmitters released from non-adrenergic, non-cholinergic nerves. 2) An increase in the concentration of external $Ca^{2+}$ enhances the release of neurotransmitters from non-adrenergic, non-cholinergic nerves which activate the $Ca^{2+}$-dependent $K^{+}$ channel. 기니피그 유문동 부위를 절제한 뒤 점막층을 박리하고 윤상근 주행방향으로 길이 10 mm, 너비 2 mm 되는 조직 절편을 만들어 수평형 실험용기에 넣어 핀으로 고정하였다. 유리미세전극을 세포내에 삽입하여 서파를 기록하면서 조직양편에 설치한 백금자극전극(직경 0.5 mm)에 강도 $10{\sim}50V$, 기간 $50{\sim}100\;{\mu}s$ 되는 자극파를 주어 신경-근 부위의 접합부 전압을 기록하여 다음과 같은 결과를 얻었다. 1) 위저부에서는 흥분성 접합부 전압이, 유문동에서는 억제성 접합부 전압이 기록되었고 유문동의 억제성 접합부 전압은 atropine($10^{-6}\;M)$과 guanethidine$(5{\times}10^{-6}\;M)$을 동시 처치했을 때 영향을 받지 않았다. 2) 세포외 $Ca^{2+}$ 농도를 높였을 때(7 mM)는 억제성 접합부 전압의 크기가 증가하고 세포외 $Mg^{2+}$ 농도를 높였을 때(5 mM)와 verapamil($10^{-5}\;M$)을 주었을 때는 억제성 접합부 전압의 크기가 감소하였다. 3) 아데노신을 투여하였을 때와 ATP를 투여했을 때는 모두 억제성 접합부 전압의 크기가 감소하였다. 4) 5-HT$(10^{-6}\;M)$을 투여했을 때는 서파크기에는 변화없이 억제성 접합부 전압의 크기만 감소하였고 5-HT type 2 길항제인 ketanserin$(5{\times}10^{-6}\;M)$을 투여했을 때는 서파크기는 현저히 감소한 반면 억제성 접합부 전압크기는 변화가 없었다. 이상의 결과로부터 유문동에서 기록되는 억제성 접합부 전압은 비아드레날린, 비콜린 동작성 신경에 의해 유발되며 $Ca^{2+}$은 비아드레날린 비콜린 동작성 신경에서 신경흥분전달물질의 유리를 촉진시키고 분비된 신경흥분전달물질로 인해 $Ca^{2+}$ 의존성 $K^{+}$ 통로가 활성화되어 억제성 접합부 전압의 크기를 증가시킨다고 사료된다.

기니피그 유문동에서 기록되는 억제성 접합부 전압에 미치는 전해질과 약물의 효과

구용숙(Goo, Yong-Sook),서석효(Suh, Suk-Hyo),이석호(Lee, Suk-Ho),황상익(Hwang, Sang-Ik),김기환(Kim, Ki-Whan) 대한생리학회 1990 대한생리학회지 Vol.24 No.1

기니피그 유문동 부위를 절제한 뒤 점막층을 박리하고 윤상근 주행방향으로 길이 10 mm, 너비 2 mm 되는 조직 절편을 만들어 수평형 실험용기에 넣어 핀으로 고정하였다. 유리미세전극을 세포내에 삽입하여 서파를 기록하면서 조직양편에 설치한 백금자극전극(직경 0.5 mm)에 강도 10 ~ 50V$</TEX>, 기간 50 ~ 100 μs 되는 자극파를 주어 신경-근 부위의 접합부 전압을 기록하여 다음과 같은 결과를 얻었다. 1) 위저부에서는 흥분성 접합부 전압이, 유문동에서는 억제성 접합부 전압이 기록되었고 유문동의 억제성 접합부 전압은 atropine(10^-6 M)과 guanethidine(5 X 10^-6 M)을 동시 처치했을 때 영향을 받지 않았다. 2) 세포외 Ca²⁺ 농도를 높였을 때(7 mM)는 억제성 접합부 전압의 크기가 증가하고 세포외 Mg²⁺ 농도를 높였을 때(5 mM)와 verapamil(10^-5 M)을 주었을 때는 억제성 접합부 전압의 크기가 감소하였다. 3) 아데노신을 투여하였을 때와 ATP를 투여했을 때는 모두 억제성 접합부 전압의 크기가 감소하였다. 4) 5-HT(10^-6 M)을 투여했을 때는 서파크기에는 변화없이 억제성 접합부 전압의 크기만 감소하였고 5-HT type 2 길항제인 ketanserin(5 X 10^-6 M)을 투여했을 때는 서파크기는 현저히 감소한 반면 억제성 접합부 전압크기는 변화가 없었다. 이상의 결과로부터 유문동에서 기록되는 억제성 접합부 전압은 비아드레날린, 비콜린 동작성 신경에 의해 유발되며 Ca²⁺은 비아드레날린 비콜린 동작성 신경에서 신경흥분전달물질의 유리를 촉진시키고 분비된 신경흥분전달물질로 인해 Ca²⁺ 의존성 K⁺ 통로가 활성화되어 억제성 접합부 전압의 크기를 증가시킨다고 사료된다. The effects of electrolytes, adenosine, ATP, 5-hydroxytryptamine (5-HT, serotonin) and ketanserin on the inhibitory junction potentials (IJPs) were investigated to clarify the interactions of these drugs with the neurotransmitters released from non-adrenergic, non-cholinergic nerves in the antrum of guinea-pig stomach. Electrical responses of antral circular muscle cells were recorded intracellularly using glass capillary microelectrode filled with 3 M KCI. All experiments were performed in Tris-buffered Tyrode soluition which was aerated with 100% O<Sub>2</sub> and kept at 35℃. The results obtained were as follows: 1) Inhibitory junction potential (IJP) was recorded in antral strip, while excitatory junction potential (EJP) was recorded in fundic strip. 2) IJP recorded in antral strip was not influenced by atropine (10^-6 M) and guanethidine (5 X 10^-6). 3) The amplitude of IJP increased in high Ca²⁺ solution, while that of IJP decreased in high Mg²⁺ solution or by Ca²⁺ antagonist (verapamil). Apamin, Ca²⁺-activated K⁺ channel blocker blocked IJP completely. 4) ATP and adenosine decreased the amplitude of IJP. 5) 5-HT decreased the amplitude of IJP with no change of the amplitude of slow waves, while ketanserin (5-HT type 2 blocker) decreased the amplitude of slow waves markedly with no change in that of IJP. From the above results, the following conclusions could be made. 1) IJP recorded in antral strip is resulted from neurotransmitters released from non-adrenergic, non-cholinergic nerves. 2) An increase in the concentration of external Ca²⁺ enhances the release of neurotransmitters from non-adrenergic, non-cholinergic nerves which activate the Ca²⁺-dependent K⁺ channel.

위 평활근의 부위별 전압-장력 관계에 관한 연구

김기환(Kim, Ki-Whan),이상진(Lee, Sang-Jin),서석효(Suh, Suk-Hyo) 대한생리학회 1989 대한생리학회지 Vol.23 No.2

Mechanical contractions and electrical activities of the fundic longitudinal and antral circular muscle fibers were investigated in order to elucidate topical differences of gastric motility. K-induced contracture was produced by exposure of muscle strips to high K Tyrode solution. Membrane potential and mechanical contraction were simultaneously recorded by conventional glass microelectrode method and single sucrose-gap technique. All experiments were performed in tris-buffered Tyrode solution which was aerated with 100% O₂ and kept 35℃. The results obtained were as follows: 1) The resting membrane potential of circular muscle cells in the antral region was about 10 mV more negative than that in the fundic region. 2) The membrane potentials decreased almost linearly as the extracellular KCI concentration was increased both in antral circular muscle cells and in fundic longitudinal muscle cells. 3) The thresholdal K concentration of K-contracture was 15 mM (membrane potential, -48 mV) for the antral circular muscle strip and 20 mM for the fundic longitudinal muscle cells. 4) The ratio of membrane permeability coefficient for Na⁺ and K⁺, P_Na/P_K(α) was 0.065 for antral circular muscle cells and was 0.108 for fundic longitudinal muscle cells. 5) K-contracture of antral and fundic smooth muscle strips showed the contracture composed of phasic and tonic components. The amplitude of the phasic component increased sigmoidally in a dose-dependent manner, whereas that of the tonic component was maximal at a concentration of 40 mM KCI and at the concentrations above or below 40 mM KCI the amplitude was reduced. 6) The inverse relationship between the amplitude of tonic component and extracellular KCI concentration in the range of 40 to 150 mM KCI was more prominent in the antral circular muscle strip than in the fundic longitudinal muscle strip, where the amplitude of the tonic component decreased less steeply and was maintained higher at the same high K concentrations. 7) The tonic component was totally dependent on the external Ca²⁺ and completely abolished by verapamil, while tile phasic component was far less dependent on the external Ca²⁺ and partially suppressed by verapamil. From the above results, the following conclusions could be made. 1) The phasic component of K-contracture is produced both by intracellular Ca²⁺ mobilization and by Ca²⁺-influx from outside, while the tonic component is generated and maintained by the Ca²⁺-influx through the potential-dependent Ca²⁺ channel. 2) The mechanism of reducing the free Ca²⁺ concentration in the myoplasm seems to be more developed in the antral circular muscle than in the fundic longitudinal muscle. 3) The lower resting membrane potential of the fundic longitudinal muscle cell reflects a relatively high P_Na/P_K ratio of about 0.108.

혈관내피세포 손상과 에스트로겐, 프로게스테론 관계에 대한 연구

김미경 ( Mi Kyoung Kim ),김지애 ( Ji Ae Kim ),전여진 ( Yeo Jin Jeon ),박종순 ( Jong Soon Park ),박미혜 ( Mi Hye Park ),서석효 ( Suk Hyo Suh ),전선희 ( Sun Hee Chun ),안정자 ( Jung Ja Ahn ),김영주 ( Young Ju Kim ) 대한산부인과학회 2007 Obstetrics & Gynecology Science Vol.50 No.3

목적: 자간전증 산모에서 에스트라디올, 에스트리올, 프로게스테론 농도 변화를 규명하고 LPC에 의한 세포 독성에 미치는 에스트로겐과 프로게스테론의 효과를 규명하고자 하였다. 연구방법: 자간전증 산모와 정상 산모를 대상으로 혈중 에스트라디올, 에스트리올, 프로게스테론, 산화성 저밀도지질단백 농도를 측정하였으며, LPC를 인간제대정맥 내피세포에 처리한 후 에스트로겐, 프로게스테론을 여러 용량으로 주었을 때 세포독성 억제 여부를 알아보았다. 결과: 에스트라디올, 에스트리올 혈중 농도는 자간전증 환자에서 정상 산모에 비해 감소하였고 산화성저밀도 지단백의 농도는 증가하였다 (P<0.05). 인간제대정맥 내피세포에 LPC를 첨가하였을 때 농도 의존적으로 세포 독성을 증가시켰으며 에스트로겐과 프로게스테론의 첨가는 각각 용량 의존적으로 세포 독성을 감소시켰다 (P<0.05). 결론: 자간전증에서의 에스트로겐, 프로게스테론 농도 감소는 자간전증의 내피세포 손상과 연관이 있으며 에스트로겐, 프로게스테론은 자간전증의 예방과 치료에 있어서 중요한 역할을 할 수 있을 것으로 생각되어 이에 대한 계속적인 연구가 필요하다 하겠다. Objective: The aim of this study were to examine the serum level of estradiol, estriol, progesterone, oxidized LDL in preeclamtic patients and to evaluate the protective effects of estrogen and progesterone against lysophosphatidylcholine (LPC) induced cell death in Human umbilical vein endothelial cells (HUVECs). Methods: We analysed the serum level of estradiol, estriol, progesterone, oxidized LDL in patients with preeclampsia and control. We used LPC to induce cell death in HUVECs. For cytotoxic assay, we did LDL assay for cell death and Resazurin assay for cell viability. HUVECs were exposed to various concentrations of LPC, LPC+estrogen, LPC+progesterone and we did cytotoxic assay. Results: The serum estradiol, estriol were lower in the preeclamptic patients (P<0.05). Oxidized LDL were higher in the preeclamptic patients(P<0.05). LPC induced cell death in a concentration-dependant manner. Estrogen or progesterone inhibited LPC-induced cell death in a concentration-dependant manner (P<0.05). Conclusion: Estrogen and progesterone attenuated LPC-induced cytotoxicity. The results suggest that Oxidized LDL induced endothelial damage in preeclampsia may be induced by low serum estradiol, estriol and progesterone levels and prevented by estrogen and progesterone addition.

관동맥의 내피세포의존성 혈관이완에 대한 마그네슘의 영향

송재관(Jae Kwan Song),고문수(Moon Soo Koh),염광섭(Kwang Seoup Yeoum),이진오(Jhin Oh Lee),강태웅(Tae Woong Kang),서정돈(Jung Don Seo),이영우(Young Woo Lee),서석효(Suk Hyo Suh),김기환(Ki Whan Kim) 대한내과학회 1990 대한내과학회지 Vol.39 No.4

N/A After the historical discovery of a soluble vasodilating substance from the vascular endothelium (endothelium-derived relaxing factor, EDRF), impaired EDRF-mediated vasorelaxation is discussed as one of the main pathogenic mechanisms of coronary artery spasm. Recently, some clinical reports that hypomagnesemia may be implicated in the induction of coronary artery spasm were presented, although there are controversial reports on the effects of the extracellular magnesium ion on endothelium-dependent vasorelaxation. Isometric contraction-relaxation was recorded in the transverse strips of porcine coronary artery to clarify the exact effects of Mg2+ on tension-development by a vasoconstrictor agent and on endothelium-dependent vasorelaxation and to predict a possible mechanism of hypomagnesemia in the induction of coronary artery spasm. The results of our study were as follows: 1) Vasoconstrictor activity of PGF2α was significantly more attenuated in the endothelium-intact transverse strips of porcine coronary artery than in the endothelium-denuded strips. 2) Lowering the magnesium concentration enhanced the vasoconstrictor activity of PGF2α while a marked reduction of isometric tension was observed with the elevation of magnesium concentration. 3) Bradykinin-induced endothelium-dependent vasorelaxation is a dose-dependent manner which was completely abolished with the pretreatment of hemoglobin. 4) Endothelium-dependent vasorelaxation of bradykinin was markedly inhibited by lowering the extracellular calcium ion concentration. 5) Change of the extracellular magnesium ion concentration did not alter the IC50 (inhibitory concentration of bradykinin causing a 50% inhibition of the maximum contraction) values of bradykinin-induced endothelium dependent vasorelaxation. From these results it is concluded that if magnesium deficiency is implicated in the induction of coronary artery spasm, the main mechanism would be direct enhancement of responsiveness of the vascular smooth muscle to the vasoconstrictors. Further study with a bioassay system and more various stimulators of EDRF secretion is necessary for exact clarification of the effects of Mg2+ on endothelium-dependent vasorelaxation.

세포외 Ca₂+ 와 Ca₂+ 길항제들이 내피세포성 이완인자의 분비에 미치는 영향

서석효 東國大學校醫學硏究所 1994 東國醫學 Vol.2 No.-

세포외 Ca2+와 Ca2+ 길항제들이 혈관 내피세포에 의한 혈관평활근 세포내 cyclic GMP 농도 상승과 내피세포 의존성 이완에 미치는 영향을 알아보고자 하였다. 2.0 kg 정도의 토끼를 pentobarbital sodium (40mg/kg)를 사용하여 마취하였으며 총경동맥을 절단 실혈시켜 즉사시켰으며, 흉부 및 복부 대동맥과 총경동맥을 절취하였다. 절취한 총경동맥과 대동맥에서 organic bath 실험방법, bioassay 실험방법, 그리고 cyclic GMP 농도 측정 방법으로 각각 세포외 Ca2+와 Ca2+ 길항제들이 내피세포 의존성 이완에 미치는 영향, 내피세포성 이완인자의 분비에 미치는 영향, 그리고 혈관평활근 세포내 cyclic GMP 농도 상승에 미치는 영향을 관찰하였다. 실험 결과는 다음과 같다. 1. 아세틸콜린에 의한 내피세포 의존성 이완은 세포외 Ca2+ 농도를 낮추었을 때 감소하였다. 2. 내피세포성 이완인자 분비 혈관을 관류하는 용액에서 Ca2+을 제거하고 관류 후 Ca2+을 주입 시험절편을 관류할 때에는 정상 Ca2+ 농도로 조정했을 때 시험절편의 이완이 감소하였다. 3. 내피세포 의존성 이완은 organic Ca2+ 길항제와 inorganic Ca2+ 길항제인 Mn2+에 의해서는 억제되지 않았다. 그러나 inorganic Ca2+ 길항제 중 La3+와 Co2+에 의해서는 억제되었다. 4. 아세틸콜린에 의한 내피세포 의존성 cyclic GMP 농도 증가는 Co2+와 Ca2+ 제거 용액에 의해서는 유의하게 억제되었으나, verapamil, nifedipine, Mn2+에 의해서는 억제되지 않았다. 이상의 실험 결과로 미루어 내피세포성 이완인자의 분비에 세포외 Ca2+이 필요하나 Ca2+ 길항제들은 내피세포성 이완인자의 분비에 영향이 없는 것으로 결론 내릴 수 있었다. The effects of extracellular Ca2+ and Ca2+ antagonosts on endothelium-dependent cyclic GMP increase in the vascular smooth muscle cells by acetylcholine and endothelium-dependent relaxation to acetylcholime were studied in rabbit arteries, using organic bath, bioassay experiment, and cyclic GMP measurement. The magnitudes of endothelium-dependent relaxations by acetylcholine were decreased by the treatment with low Ca2+ solution. EDRF release was attenuated with Ca2+ free solution. Endothelium-dependent relaxations by acetylcholine were not attenuated with the treatment of Mn2+ or organic Ca2+-antagonists. Co2+ and La3+ inhibited endothelium-dependent relaxation. Cyclic GMP levels of the strips treated with Co2+ and Ca2+ -free solution were significantly decreased compared with that of the strips with intact endothelium. Whereas, cyclic Gmp levels of the strips treated with verapamil, nifedipine, and Ca2+ were not decreased, compared with that of the strips with intact endothelium. Therefore, it could be concluded that extracellular Ca2+ is necessary for EDRF release but Ca2+-antagonists have no effect no the release.