Calcium transport and Ca(++)-ATPase activity in spermatozoal plasma membrane vesicles of nifedipine-administered guinea pigs.
Spermatozoal plasma membrane vesicles isolated from distal portion of the epididymis and vas deferens were found to contain Ca(++)-activated ATPase and calcium transport activities. Nifedipine was administered at two different doses (1.0 and 2.5 mg/kg b.w./day) and the effect was observed for both short- (4 week) and long-term (12 week) period. The cellular ionic calcium content and Ca(++)-ATPase activity were observed to be enhanced in the drug-treated animals. The recovery studies carried out after 4 and 6 weeks of withdrawal of the drug treatment exhibited partial to complete restoration of observed changes. The stimulatory rather than inhibitory effect of Nifedipine, a specific calcium channel blocker, on calcium uptake may suggest that voltage-sensitive calcium channels may be lacking in guinea pig spermatozoa. The stimulatory effect of the drug is speculated to be either by inhibition of Na(+)-Ca++ antiporter or G-protein activated agonistic effect or probably due to altered physicochemical properties of the drug-treated sperm plasma membranes.
Juneja
R
R
Department of Obstetrics & Gynaecology, Postgraduate Institute of Medical Education and Research, Chandigarh, India.
Gupta
I
I
Wali
A
A
Chakravarti
R N
RN
Majumdar
S
S
D015720:5'-Nucleotidase / Q000032:analysis; D000818:Animals; D002118:Calcium / Q000493:pharmacokinetics*; D000252:Calcium-Transporting ATPases / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D008297:Male; D009543:Nifedipine / Q000494:pharmacology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis; D013094:Spermatozoa / Q000378:metabolism*; D013385:Succinate Dehydrogenase / Q000032:analysis
D013385:Succinate Dehydrogenase; D015720:5'-Nucleotidase; D000252:Calcium-Transporting ATPases; D000254:Sodium-Potassium-Exchanging ATPase; D009543:Nifedipine; D002118:Calcium