Verapamil stimulates Ca(++)-uptake and Ca(++)-ATPase in plasma membrane vesicles of guinea pig spermatozoa.
Verapamil, a potent calcium channel blocker, was administered orally at three different doses to guinea pigs for both short- (4 weeks) and long-term (12 weeks) effects. The drug treatment stimulated Ca(++)-transport and Ca(++)-activated ATPase in isolated plasma membrane vesicles of guinea pig spermatozoa. Ca(++)-uptake studies exhibited partial to complete restoration of stimulated Ca(++)-transport during recovery period, whereas the CA(++)-activated ATPase system remained stimulated even after 4 and 6 weeks of withdrawal of the drug treatment. The lack of inhibitory effect of verapamil on Ca(++)-uptake ruled out the involvement of calcium channels in spermatozoal calcium uptake in guinea pigs. The stimulatory effect of the drug on CA(++)-uptake, on the other hand, might indicate the possible capability of this lipophilic compound to induce favourable changes in the lipid microenvironment of the membrane, wherein the integral membrane proteins operate.
Juneja
R
R
Department of Obstetrics and Gynecology, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
Gupta
I
I
Wali
A
A
Chakravarti
R N
RN
Majumdar
S
S
D000818:Animals; D002118:Calcium / Q000493:pharmacokinetics*; D000252:Calcium-Transporting ATPases / Q000493:pharmacokinetics*; D002462:Cell Membrane / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D008297:Male; D013094:Spermatozoa / Q000648:ultrastructure*; D014700:Verapamil / Q000494:pharmacology*
D014700:Verapamil; D000252:Calcium-Transporting ATPases; D002118:Calcium