Effects of castration on alpha 1-adrenoceptor subtypes in the rat aorta.
The expression of alpha 1-adrenoceptor subtypes in several tissues is regulated by gonadal hormones. In this study, we investigated whether castration regulates the alpha 1-adrenoceptor subtypes mediating the contractions of the aorta from male rats to noradrenaline. Noradrenaline induced similar concentration-dependent contractions in the aorta from control and castrated rats. Treatment of the aorta from both control and castrated rats with the alpha 1B/alpha 1D-adrenoceptor alkylating agent chloroethylclonidine resulted in approximately 1600-fold rightward shift in the concentration-response curves to noradrenaline. The pA2 values found for WB 4101, benoxathian (alpha 1A-selective) and BMY 7378 (alpha 1D-selective) indicate that alpha 1D-adrenoceptors are involved in the contractions of the aorta from control and castrated rats to noradrenaline. However, there was a 15-fold difference between the pKB estimated through the lowest effective concentrations of the alpha 1A-adrenoceptor selective antagonist 5-methyl-urapidil in the aorta from control and castrated rats. The pKB estimated in aorta from control rats is consistent with the interaction with alpha 1D-adrenoceptors (7.58 +/- 0.06), while that calculated in organs from control rats is consistent with alpha 1A-adrenoceptors (8.76 +/- 0.09). These results suggest that castration induces plasticity in the alpha 1-adrenoceptor subtypes involved in the contractions of the aorta to noradrenaline.
Morais
Paola de Lucena
Pde L
Department of Pharmacology, Instituto de Biociências, UNESP, 18618-000 Botucatu, SP, Brazil.
Campos
Marcelo
M
Pupo
André S
AS
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000378:metabolism*; D003000:Clonidine / Q000031:analogs & derivatives* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009638:Norepinephrine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D009919:Orchiectomy; D051381:Rats; D017208:Rats, Wistar; D018340:Receptors, Adrenergic, alpha-1 / Q000502:physiology*; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D018340:Receptors, Adrenergic, alpha-1; D014662:Vasoconstrictor Agents; C051731:chlorethylclonidine; D003000:Clonidine; D009638:Norepinephrine