Decreased density of binding sites for the Ca2+ channel antagonist [3H]isradipine after denervation of rat vas deferens.
Radioligand binding assays were performed with the selective antagonist of dihydropyridine-sensitive Ca2+ channels [3H]PN200-110 (isradipine) in rat vas deferens, before and 7 days after denervation, and data were compared with those obtained for K(+)-induced contractions, which are Ca(2+)-dependent. The density (Bmax) of dihydropyridine binding sites was decreased to almost one-third of its normal value after denervation. The respective affinity (KD) was not significantly changed. In addition, it was observed that the K(+)-induced tonic contraction, which corresponded to 55 +/- 2% of the respective phasic contraction, was decreased to 41 +/- 3% after denervation. It is assumed that the decreased density of Ca2+ channels causes a decrease in K(+)-induced influx of Ca2+ and consequently of the corresponding tonic contraction. These results indicate that autonomic innervation can regulate the density of dihydropyridine-sensitive Ca2+ channels in the rat vas deferens.
Jurkiewicz
A
A
Department of Pharmacology, Escola Paulista de Medicina, São Paulo, Brazil.
Lafayette
S S
SS
Nunes
S H
SH
Martini
L C
LC
Do Carmo
L G
LG
Wanderley
A G
AG
Jurkiewicz
N H
NH
D000818:Animals; D001665:Binding Sites / Q000187:drug effects; D015220:Calcium Channels / Q000187:drug effects; D003714:Denervation; D004095:Dihydropyridines / Q000494:pharmacology; D017275:Isradipine / Q000378:metabolism*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D014649:Vas Deferens / Q000187:drug effects / Q000378:metabolism*
D015220:Calcium Channels; D004095:Dihydropyridines; D011189:Potassium Chloride; C038806:1,4-dihydropyridine; D017275:Isradipine