Alteration in sarcoplasmic reticulum-dependent contraction of tail arteries in response to caffeine and noradrenaline in spontaneously hypertensive rats.
Since the membrane Ca2+ handling properties of the arterial smooth muscle sarcoplasmic reticulum may be altered in genetic hypertension, we studied caffeine- and noradrenaline-induced contractions in tail arteries from spontaneously hypertensive rats (SHR) at the prehypertensive stage (4 weeks old) and from age-matched Wistar-Kyoto rats (WKY). After the sarcoplasmic reticulum had been loaded with Ca2+ by pretreatment with physiological Ca2+ solution, caffeine- and noradrenaline-induced contractions of the tail arteries, measured in a Ca2(+)-free solution [containing 0.1 mmol/l ethyleneglycol-bis-(beta-aminoethylether)-N,N,N',N'-tetraace tic acid], were smaller in SHR than in WKY. After caffeine-releasable Ca2+ in the sarcoplasmic reticulum had been depleted by pretreatment with the Ca2(+)-free solution, the caffeine-induced arterial contractions in a low-Ca2+ (0.5 mmol/l) solution were smaller in SHR than in WKY. The Ca2+ concentration-tension relationship in skinned arterial fibres was similar in WKY and SHR. These data suggest that the ability of the sarcoplasmic reticulum to take up and store caffeine- and noradrenaline-releasable Ca2+ is decreased in SHR. The development of hypertension in SHR may be explained by an impaired function of the sarcoplasmic reticulum in arterial smooth muscle.
Dohi
Y
Y
Department of Pharmacology, Nagoya City University Medical School, Japan.
Aoki
K
K
Fujimoto
S
S
Kojima
M
M
Matsuda
T
T
D000818:Animals; D001158:Arteries / Q000187:drug effects; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D003285:Contractile Proteins / Q000378:metabolism; D006973:Hypertension / Q000378:metabolism / Q000503:physiopathology*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D009638:Norepinephrine / Q000494:pharmacology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012503:Saponins; D012519:Sarcoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D013623:Tail / Q000098:blood supply*
D003285:Contractile Proteins; D012503:Saponins; D002110:Caffeine; D002118:Calcium; D009638:Norepinephrine