Effects of castration on contraction and alpha(1)-adrenoceptor expression in rat prostate.
1. The prostate function is regulated by androgens and alpha-adrenergic activity. Clinically, antiandrogens and/or alpha(1)-adrenergic antagonists are commonly used to treat symptomatic prostatic hypertrophy. To elucidate the effects of androgen deprivation on prostate contractility via alpha(1)-adrenoceptor, the characteristics and expression of alpha(1)-adrenoceptors were examined in castrated rats. 2. Isolated prostate strips from intact and castrated rats were subjected to a phenylephrine stimulated contraction. Prazosin (10 nM), [(3)H]-prazosin and phenoxybenzamine (3 - 300 nM) were used for inhibition assay, receptor characterization and partial alkylation of alpha-adrenoceptor, respectively. The mRNA content of three subtypes of alpha-adrenoceptors was determined by reverse transcription combined with polymerase chain reaction (RT - PCR). 3. Contractile response to phenylephrine increased in castrated rats, which could be explained by a relative increase of the stromal component. A lowered contraction potency was also noted in castrated rats. Receptor binding assay indicated minimal changes in the affinity or density of alpha(1)-adrenoceptor. Escalating alkylation of the alpha(1)-adrenoceptor population resulted in a rightward shift in the contraction-response curves before depressing maximal contractile force, and the suppression was detected at lower doses in castrated rats. RT - PCR study confirmed the expression of three types of alpha(1)-adrenoceptor, alpha(1a), alpha(1b) and alpha(1d)-adrenoceptors, in intact rat prostate, and revealed that alpha(1a)-adrenoceptor, but not alpha(1b) or alpha(1d)-adrenoceptors, was down-regulated in castrates. 4. The results show that androgen deprivation suppressed alpha(1)-adrenergic contractility of rat prostate strips, and the suppression was associated with down-regulation of receptor reserve for the alpha(1a)-adreneroceptor population expressed in intact rat prostate.
Homma
Y
Y
Department of Urology, Tokyo University Branch Hospital, 3-28-6 Mejirodai, Bunkyo-ku, Tokyo 112-8688, Japan. homma-uro@h.u-tokyo.ac.jp
Hamada
K
K
Nakayama
Y
Y
Tsujimoto
G
G
Kawabe
K
K
D058668:Adrenergic alpha-1 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists / Q000378:metabolism / Q000494:pharmacology; D000478:Alkylation; D000818:Animals; D001667:Binding, Competitive; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D066298:In Vitro Techniques; D008297:Male; D008566:Membranes / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009919:Orchiectomy; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000378:metabolism / Q000494:pharmacology; D011467:Prostate / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D018340:Receptors, Adrenergic, alpha-1 / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014662:Vasoconstrictor Agents / Q000494:pharmacology
D058668:Adrenergic alpha-1 Receptor Antagonists; D000317:Adrenergic alpha-Antagonists; D012333:RNA, Messenger; D018340:Receptors, Adrenergic, alpha-1; D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D011224:Prazosin