title: Possible mechanisms of stimulatory action of papaverine on calcium-uptake by rat uterine microsomal fraction.
abstract: Effects of papaverine and cyclic AMP on Ca-uptake by the microsomal fraction from rat uterus were studied. Papaverine (3 x 10(-5) M) potentiated Ca-uptake by the microsomal fraction in the presence of potassium oxalate. However, cyclic AMP and MIX (3-isobutyl-1-methylxanthine; 1 mM), a potent phosphodiesterase inhibitor, did not influence Ca-uptake by the microsomal fraction in the presence of potassium oxalate. Cyclic AMP in concentrations of 10(-8) to 10(-4) M did not influence Ca-uptake by the microsomal fraction in the presence of potassium oxalate. In the absence of potassium oxalate, papaverine and Aspaminol (1,1,-diphenyl-3-piperidinobutanol hydrochloride), a nonspecific smooth muscle relaxant, inhibited Ca-uptake by the microsomal fraction and cyclic AMP had no influence on this uptake. These results suggest that papaverine potentiated Ca-uptake by membranes such as sarcoplasmic reticulum, in the presence of potassium oxalate and inhibited Ca-uptake by the plasma membrane-derived vesicles in the absence of potassium oxalate. These results suggest that relaxation of smooth muscle by papaverine is related to a cyclic AMP-independent mechanism as well as to a mechanism mediated via cyclic AMP.
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism*; D009124:Muscle Proteins / Q000378:metabolism; D010070:Oxalates / Q000494:pharmacology; D019815:Oxalic Acid; D010208:Papaverine / Q000494:pharmacology*; D010880:Piperidines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013268:Stimulation, Chemical; D013997:Time Factors; D014599:Uterus / Q000187:drug effects / Q000378:metabolism*
chemical_list: D009124:Muscle Proteins; D010070:Oxalates; D010880:Piperidines; D019815:Oxalic Acid; D010208:Papaverine; D000242:Cyclic AMP; D002118:Calcium