The effects of bromoacetylalprenololmenthane on the responses to isoprenaline of the left ventricle from normo-, prehyper- and hypertensive rats.
1. We have studied the effects of bromoacetylalprenololmenthane (BAAM), a very slowly reversible beta-adrenoceptor antagonist, on the responses of the left ventricle of 5 and 22 week old Wistar Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs) to isoprenaline. At 5 weeks the SHRs were prehypertensive and at 22 weeks they had hypertension-induced hypertrophy of the left ventricle. 2. The mean potency of isoprenaline on the left ventricle from 5 week old WKY was similar to that obtained on left ventricle with BAAM at 10(-6) M for 30 min, there was a parallel rightward shift of the isoprenaline concentration-response curves. Treatment with a higher concentration of BAAM (10(-5)M) caused non-parallel rightward shifts of the concentration-response curves, with a depression of the isoprenaline maximum responses. These data were used to derive affinity (KA) values for isoprenaline. The mean isoprenaline KA value on the left ventricle from 5 week old WKY was 2.44 x 10(-6)M, and similar KA values were obtained on the left ventricles from 22 week old WKY and 5 and 22 week old SHRs. On all the left ventricles tested, isoprenaline produced a half maximal response by occupying less than 1%, and a near maximal response by occupying about 5% of the available beta(1)-adrenoceptors. 4. This study has shown that there are no differences in the cardiac responses to isoprenaline at beta(1)-adrenoceptors, isoprenaline KA values or the beta(1)-adrenoceptor reserve for isoprenaline on the SHR left ventricle in prehypertension or in the early stages of hypertension-induced hypertrophy.
Doggrell
S A
SA
Department of Pharmacology and Clinical Pharmacology, School of Medicine, University of Aukland, New Zealand.
Mistry
D N
DN
Henderson
C J
CJ
D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000526:Alprenolol / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation; D005260:Female; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D006352:Heart Ventricles / Q000187:drug effects / Q000648:ultrastructure; D006973:Hypertension / Q000503:physiopathology*; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism; D016277:Ventricular Function, Left / Q000187:drug effects
D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D011943:Receptors, Adrenergic, beta; C045331:bromoacetylalprenololmenthane; D000526:Alprenolol; D007545:Isoproterenol