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Titolo:
CA2-TRANSIENTS INDUCED BY K+ CHANNEL OPENERS IN ISOLATED CORONARY CAPILLARIES()
Autore:
LANGHEINRICH U; SCHNITZLER MMY; DAUT J;
Indirizzi:
UNIV MARBURG,INST NORMALE & PATHOL PHYSIOL,DEUTSCHHAUSSTR 2 D-35037 MARBURG GERMANY
Titolo Testata:
Pflugers Archiv
fascicolo: 3, volume: 435, anno: 1998,
pagine: 435 - 438
SICI:
0031-6768(1998)435:3<435:CIBKCO>2.0.ZU;2-Q
Fonte:
ISI
Lingua:
ENG
Soggetto:
ENDOTHELIAL-CELLS; CALCIUM INFLUX; HYPERPOLARIZATION;
Keywords:
ATP-SENSITIVE K+ CHANNEL; CALCIUM; CAPILLARY; ENDOTHELIAL CELL; K+ CHANNEL OPENER; MEMBRANE POTENTIAL; MICROFLUOROMETRY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
8
Recensione:
Indirizzi per estratti:
Citazione:
U. Langheinrich et al., "CA2-TRANSIENTS INDUCED BY K+ CHANNEL OPENERS IN ISOLATED CORONARY CAPILLARIES()", Pflugers Archiv, 435(3), 1998, pp. 435-438

Abstract

To study the role of endothelial ATP-sensitive K+ channels in the regulation of vascular tone we examined the intracellular calcium concentration ([Ca2+](i)) in coronary capillaries consisting only of endothelial cells. Coronary capillary fragments were isolated enzymatically from the guinea-pig heart and [Ca2+](i) was determined by microfluorometry of fura-2 loaded cells. Low concentrations of the K+ channel openerdiazoxide, which caused pronounced glibenclamide-sensitive hyperpolarization in capillaries, induced a rapid, transient rise in [Ca2+](i) followed by a sustained elevation of [Ca2+](i) (19 of 40 experiments). [Ca2+](i) in the endothelial cells increased from 32 +/- 7 nM at rest to 66 +/- 11 nM at the peak (n = 19). One third of the [Ca2+](i)-transients showed irregular oscillations of [Ca2+](i). No significant difference in the [Ca2+](i)-response induced by 100 nM or 1 mu M diazoxide was found. Similar results were obtained with the K+ channel opener rilmakalim. Simultaneous measurements of the membrane potential and [Ca2](i) with fluorometric methods indicated that the hyperpolarization but not the [Ca2+](i)-transient could be repeatedly induced in a singlecapillary by the K+ channel openers. Electrophysiological recordings of the membrane potential using the ''perforated patch'' method (n = 4), showed that rilmakalim (1 mu M) induced hyperpolarization of capillaries towards the K+ equilibrium potential, confirming our fluorometric measurements. In conclusion, for the first time, these data indicatethat K+ channel openers induce [Ca2+](i)-transients in microvascular endothelial cells. This raises the possibility that these drugs not only act as synthetic vasoactive factors via hyperpolarizing smooth muscle cells but also via NO release of microvascular endothelial cells. Interestingly, only 100 nM diazoxide was sufficient for a maximal response, suggesting the expression of a new type of K-ATP-channel in coronary capillaries characterised by high sensitivity to diazoxide.

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Documento generato il 02/12/20 alle ore 17:35:09