Ca(2+)-sensitivity of portal vein circular muscle from normotensive and hypertensive rats.
Contractile sensitivity to Ca2+ was studied in rat portal vein circular muscle isolated from normotensive Wistar Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP). There was no difference in resting membrane potential between WKY and SHRSP. Elevation of extracellular K+ concentration induced similar increase in tension in preparations from WKY and SHRSP. High K(+)-depolarized preparation developed tension increase when extracellular Ca2+ concentration was increased. The sensitivity to extracellular Ca2+ was similar in preparations from WKY and SHRSP. Permeabilized preparation contracted when free Ca2+ concentration was increased. Sensitivity of permeabilized preparation to Ca2+ was similar in preparations from WKY and SHRSP. These results indicate that regulation of contraction by Ca2+ was similar between WKY and SHRSP. Since there was no change in high K-induced contraction in intact preparations or Ca-induced contraction in permeabilized preparations, there seemed to be no difference in Ca2+ influx via voltage-dependent channels in portal vein circular muscle from WKY and SHRSP.
Shimamura
K
K
Research Institute of Hypertension, Kinki University, Osaka, Japan. reshyper@med.kindai.ac.jp
Zou
L B
LB
Matsuda
K
K
Yamamoto
K
K
Sekiguchi
F
F
Sunano
S
S
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D006973:Hypertension / Q000503:physiopathology*; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D011169:Portal Vein / Q000187:drug effects* / Q000503:physiopathology; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
D011188:Potassium; D002118:Calcium