ETB receptors on aortic smooth muscle cells of spontaneously hypertensive rats.
The effect of the agonist sarafotoxin 6c (S6c), selective for endothelin (ET) receptor subtype B (ETB), on cytosolic free Ca2+ concentrations ([Ca2+]i) was determined by fura-2 methodology using aortic smooth muscle cells (ASMC) isolated from spontaneously hypertensive rats (SHR) and two normotensive strains, Wistar-Kyoto (WKY) and Sprague-Dawley (SD) rats. The basal [Ca2+]i was significantly higher in the ASMC of SHR (139 +/- 8 nM) than WKY (107 +/- 7 nM) and SD (102 +/- 4 nM) rats. S6c produced concentration-dependent elevations in [Ca2+]i in the ASMC of WKY and SHR, whereas it did not evoke significant increases in the [Ca2+]i levels in the ASMC of SD rats. The peak [Ca2+]i levels observed with maximal concentrations of S6c (500 nM) was higher (P < 0.01) in the SHR (346 +/- 36 nM) than the WKY group (148 +/- 19 nM). The natural nonselective agonist, ET-1, evoked maximal [Ca2+]i in the ASMC of SHR, WKY, and SD rats of 635 +/- 43, 304 +/- 19, and 289 +/- 24 nM, respectively. Depletion of extracellular Ca2+ concentration led to the reduction of the peak [Ca2+]i response to ET-1 by 60 and 40% in the WKY and SHR cells, respectively, whereas the response to S6c remained unaffected. The ETA-selective antagonist, BQ-123 (1 microM), did not affect the [Ca2+]i response to S6c, whereas it attenuated the response to ET-1 by 90 and 70% in the WKY and SHR cells, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
Batra
V K
VK
Department of Pharmacology, University of Saskatchewan, Saskatoon, Canada.
McNeill
J R
JR
Xu
Y
Y
Wilson
T W
TW
Gopalakrishnan
V
V
D000818:Animals; D001011:Aorta / Q000166:cytology / Q000378:metabolism*; D001794:Blood Pressure; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D016232:Endothelins / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009994:Osmolar Concentration; D010456:Peptides, Cyclic / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D017207:Rats, Sprague-Dawley; D017466:Receptors, Endothelin / Q000145:classification / Q000378:metabolism*; D014757:Viper Venoms / Q000494:pharmacology
D016232:Endothelins; D010456:Peptides, Cyclic; D017466:Receptors, Endothelin; D014757:Viper Venoms; C057354:sarafotoxins s6; C072247:cyclo(Trp-Asp-Pro-Val-Leu); D002118:Calcium