Nifedipine-resistant Ca(++)-induced contraction in tail artery of spontaneously hypertensive rats.
Nifedipine-resistant Ca(++)-induced contractions (NR-Ca(++)-contraction) were compared in the tail arteries from SHRs and WKYs (5 and 13 week old). NR-Ca(++)-contraction of tail artery was defined as follows: Ca(++)-induced contraction in the presence of norepinephrine (NE) (10(-5) M) or 5-hydroxytryptamine (5-HT) (10(-5) M) in Ca(++)-free medium containing EGTA (0.1 mM) and nifedipine (10(-6) M). NR-Ca(++)-contractions in arteries from 5 week old SHRs and WKYs were not different. In contrast, NR-Ca(++)-contractions in arteries from 13 week old SHRs were about 2-fold greater than in arteries from 13 week old WKYs. In arteries from 13 week old WKYs and SHRs, nitroglycerin (10(-5) M) significantly reduced the NR-Ca(++)-contraction in the presence of 5-HT but not in the presence of NE. The reduction was inhibited by the presence of methylene blue (3 x 10(-6) M). 8-Bromo-cGMP (10(-4) M) reduced significantly the NR-Ca(++)-contraction in the presence of 5-HT in arteries from 13 week old SHRs and WKYs. The present experiments clearly demonstrated that the NR-Ca(++)-contractions (both in the presence of NE and 5-HT) in 13 week old SHRs were significantly greater than those in arteries from 13 week old WKYs. These results suggest that in addition to an increase in voltage-operated Ca++ mobilization reported by others, an increase in NR-Ca++ mobilization may contribute to the development of hypertension in SHR.
Kurahashi
K
K
Pharmacology Division, Kyoto University, Japan.
Akimoto
Y
Y
Usui
H
H
Jino
H
H
D000818:Animals; D001158:Arteries / Q000187:drug effects* / Q000502:physiology / Q000503:physiopathology; D001794:Blood Pressure; D002118:Calcium / Q000494:pharmacology*; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008751:Methylene Blue / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology / Q000503:physiopathology; D009543:Nifedipine / Q000494:pharmacology*; D005996:Nitroglycerin / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012701:Serotonin / Q000494:pharmacology
C016276:8-bromocyclic GMP; D012701:Serotonin; D004533:Egtazic Acid; D005996:Nitroglycerin; D006152:Cyclic GMP; D009543:Nifedipine; D002118:Calcium; D008751:Methylene Blue; D009638:Norepinephrine