title: Effects of papaverine on calcium efflux and contractility in superfused rat left atria.
abstract: The effects of papaverine upon force of contraction, maximal rate of contraction, maximal rate of relaxation and 45Ca efflux were studied in isolated superfused rat left atria electrically driven at 1 Hz. Papaverine (3 X 10(-5) mol/l, increased developed tension (from 5.35 +/- 1.17 mN to 7.18 +/- 1.51 mN) by 1.8 +/- 0.41 mN (+33%, p less than 0.01) and maximal rate of contraction (+T) by 34.5 +/- 13% (p less than 0.05). In all experimental conditions tested, papaverine increased the rate of 45Ca efflux. The amount by which papaverine increased 45Ca efflux was 175 +/- 41 nmoles . g wet wt-1 and 304 +/- 76 nmoles . g wet wt-1, in the presence and in the absence of caffeine, respectively. The plot of changes in 45Ca efflux versus changes in developed tension fitted to a straight line (r = +0.56, n = 17, p less than 0.05), with a slope and intercept of 42 nmoles Ca . mN-1 . g wet wt-1 and -0.47 mN respectively, suggesting an association between the changes induced by papaverine in force development and increased 45Ca efflux.
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D004558:Electric Stimulation; D005260:Female; D006325:Heart Atria / Q000187:drug effects / Q000378:metabolism; D066298:In Vitro Techniques; D009200:Myocardial Contraction / Q000187:drug effects*; D010208:Papaverine / Q000494:pharmacology*; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
chemical_list: D010208:Papaverine; D002118:Calcium