Low dihydropyridine receptor density in vasa deferentia of castrated rats.
Radioligand binding studies in crude membrane preparations of vasa deferentia of normal rats, with the 1,4-dihydropyridine (+)-[3H]-PN200-110 (isradipine) showed typical saturation isotherms. The binding exhibited a KD of 259 +/- 60 pM and Bmax of 144 +/- 20 fmol mg-1 protein. The low KD and the stereoselective displacement of (+)-[3H]-PN200-110 binding by (+)- and (-)-PN200-110 and by nifedipine suggests that these tissues contain dihydropyridine receptors probably coupled to voltage-sensitive, L-type calcium channels. In membrane preparations from vasa deferentia from rats castrated 30 days previously the maximum specific binding was 25 +/- 10 fmol mg-1 protein, representing only 11% of total binding; thus, the calculation of reliable KD values was not feasible. These findings suggest that a testicular hormone, possibly testosterone, plays an important role in the regulation of dihydropyridine-sensitive, voltage-dependent calcium channels in the rat vas deferens.
Castillo
C J
CJ
Department of Pharmacology, Escola Paulista de Medicina, São Paulo, Brazil.
Lafayette
S
S
Caricati-Neto
A
A
Sette
M
M
Jurkiewicz
N H
NH
García
A G
AG
Jurkiewicz
A
A
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels; D004095:Dihydropyridines / Q000494:pharmacology; D017275:Isradipine; D007700:Kinetics; D008297:Male; D008566:Membranes / Q000187:drug effects; D009543:Nifedipine / Q000494:pharmacology; D009919:Orchiectomy; D011869:Radioligand Assay; D051381:Rats; D011919:Rats, Inbred Strains; D011978:Receptors, Nicotinic / Q000032:analysis*; D014649:Vas Deferens / Q000737:chemistry*
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004095:Dihydropyridines; D011978:Receptors, Nicotinic; D009543:Nifedipine; D017275:Isradipine