Effects of drugs that activate or inhibit calcium channels on contraction of the aorta from hypertensive rabbits.
A comparison was made of contractile responses of aortic rings isolated from rabbits with perinephritis hypertension and sham-operated rabbits. Contraction was elicited by potassium, noradrenaline or 11,9-epoxymethano PGH2 (a thromboxane A2 mimetic). Except for the maximum response to noradrenaline, there were no significant differences in the responses to KCl or 11,9-epoxymethano PGH2 between normotensive and hypertensive rabbit aorta preparations. Hypertensive rabbit aorta preparations were more susceptible to the calcium channel inhibitors nifedipine and nisoldipine, but less sensitive to a calcium channel facilitator Bay K 8644 than were normotensive preparations. These results suggest that calcium regulatory mechanisms undergo changes during the development of hypertension. We have also found that nifedipine and nisoldipine show high inhibitory potency in the calcium channel inhibitor-sensitive contractile component during alpha-adrenoceptor activation and appear to be weak competitive antagonists at thromboxane A2 receptor sites.
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D006973:Hypertension / Q000503:physiopathology*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009543:Nifedipine / Q000031:analogs & derivatives / Q000494:pharmacology; D015737:Nisoldipine; D011189:Potassium Chloride / Q000494:pharmacology; D011817:Rabbits
D002121:Calcium Channel Blockers; D007473:Ion Channels; D015737:Nisoldipine; D011189:Potassium Chloride; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009543:Nifedipine