Drug effects on myocardial 45Ca uptake in conscious rats.
The myocardial content of 45Ca++ in conscious rats is increased by single s.c. injections of sympathomimetics. A dose dependent inhibition of this effect is achieved by simultaneous administration of calcium antagonists or beta-receptor blocking agents. The myocardial 45Ca++ content of conscious rats is increased by i.v. administration of dibutyrylcycloadenosinemonophosphate (DBcAMP). The effect of the cyclic nucleotide is suppressed only by a calcium antagonist but not by a beta-receptor blocker. The following conclusions may be drawn: 1. Calcium antagonists and beta-sympatholytics have different sites of action in the heart. 2. The lack of DBcAMP-antagonism of the beta-sympatholytics permits a simple discrimination between both types of substances. After pretreatment with sympathomimetics for 7 days (0.3 mg/kg isoprenaline s.c.), neither high doses of isoprenaline nor doses of DBcAMP and aminophylline increased the myocardial 45Ca content in rats. This effect only lasted briefly (for about two weeks); the site of its action is so far unknown.
D000319:Adrenergic beta-Antagonists / Q000494:pharmacology*; D000628:Aminophylline / Q000494:pharmacology; D000818:Animals; D001285:Atropine / Q000494:pharmacology; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004837:Epinephrine / Q000494:pharmacology; D005110:Extracellular Space / Q000032:analysis; D007545:Isoproterenol / Q000097:blood / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D011412:Propanolamines / Q000494:pharmacology; D051381:Rats; D013566:Sympathomimetics / Q000494:pharmacology*; D013997:Time Factors; D014700:Verapamil / Q000494:pharmacology*
D000319:Adrenergic beta-Antagonists; D011412:Propanolamines; D013566:Sympathomimetics; D000628:Aminophylline; D003994:Bucladesine; D001285:Atropine; D014700:Verapamil; D007545:Isoproterenol; D002118:Calcium; D009638:Norepinephrine; D004837:Epinephrine; D010646:Phentolamine