Increased Ca2+ buffering function of sarcoplasmic reticulum in small mesenteric arteries from spontaneously hypertensive rats.
We compared the Ca2+ buffering function of the superficial sarcoplasmic reticulum (SR) during rest and during contraction in endothelium-denuded strips of small mesenteric arteries from 13-week-old spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). The addition of caffeine (1-20 mM) caused a transient contraction in both strains, and the contraction was significantly larger in SHR. When the SR Ca2+ buffering function was eliminated by cyclopiazonic acid (CPA; 10 microM) or thapsigargin (100 nM), both of which inhibit SR Ca2+-ATPase, or by ryanodine (10 microM), which depletes the SR Ca2+, there was a larger contraction in SHR than in WKY, suggesting that the Ca2+ buffering function of the SR during rest is more important in SHR than in WKY. Judging from the augmenting effects of these three agents on the contractile responses to Bay k 8644 (1-300 nM), an agonist of L-type Ca2+ channels, or norepinephrine (10(-9)-10(-4) M), an alpha-adrenoceptor agonist, the effects were significantly greater in SHR than in WKY. We conclude that 1) the Ca2+ influx during rest and during stimulation with Bay k 8644 or norepinephrine is strongly buffered by Ca2+ uptake into the superficial SR in the small mesenteric arteries from SHR and WKY; and 2) these Ca2+ buffering functions are increased in SHR because of the larger capacity of SR for Ca2+ storage.
Nomura
Yukiko
Y
Department of Pharmacology, Nagoya City University Medical School, Nagoya, Japan.
Asano
Masahisa
M
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D002021:Buffers; D002118:Calcium / Q000378:metabolism*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006973:Hypertension / Q000378:metabolism* / Q000503:physiopathology; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D008638:Mesenteric Arteries / Q000187:drug effects / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR / Q000378:metabolism*; D011921:Rats, Inbred WKY; D012433:Ryanodine / Q000494:pharmacology; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D019284:Thapsigargin / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects
D000316:Adrenergic alpha-Agonists; D002021:Buffers; D002120:Calcium Channel Agonists; D004791:Enzyme Inhibitors; D007211:Indoles; D012433:Ryanodine; D019284:Thapsigargin; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D002118:Calcium; D009638:Norepinephrine; C000543:cyclopiazonic acid