RESUMO
The dual regulation of cyclic AMP accumulation was studied in rat prostatic epithelial cells incubated with somatostatin, vasoactive intestinal peptide (VIP), and the beta-adrenergic agent isoproterenol. Somatostatin noncompetitively inhibited the stimulatory effect of VIP and isoproterenol, but it did not alter basal cyclic AMP levels. In addition to the multifactorial regulation of the cyclic AMP system in rat prostatic epithelium, these results suggest that somatostatin may play a physiological role at this level.
Assuntos
AMP Cíclico/biossíntese , Isoproterenol/antagonistas & inibidores , Próstata/efeitos dos fármacos , Somatostatina/farmacologia , Peptídeo Intestinal Vasoativo/antagonistas & inibidores , Inibidores de Adenilil Ciclases , Animais , Células Epiteliais , Epitélio/efeitos dos fármacos , Masculino , Próstata/citologia , RatosRESUMO
1. The administration of 125I-labelled growth hormone-releasing factor (GRF) analogue 1-29NH2 by intravenous, subcutaneous or intraperitoneal injection to rats leads to rapid (i.v.) or slow (s.c. and i.p.) increases in plasma radioactivity followed by extensive breakdown of the peptide. 2. Tissues possessing GRF-like immunoreactivity such as gastric antrum (but not fundus), duodenum and ileum showed in vitro specific uptake of 125I-GRF probably mediated by vasoactive intestinal peptide (VIP) receptors. 3. Pituitary (the primary target organ for GRF) but neither thyroid nor parathyroid exhibited specific uptake of 125I-GRF.
Assuntos
Hormônio Liberador de Hormônio do Crescimento/análogos & derivados , Hormônio Liberador de Hormônio do Crescimento/metabolismo , Fragmentos de Peptídeos/sangue , Animais , Feminino , Hormônio Liberador de Hormônio do Crescimento/administração & dosagem , Hormônio Liberador de Hormônio do Crescimento/sangue , Injeções Intraperitoneais , Injeções Intravenosas , Injeções Subcutâneas , Fragmentos de Peptídeos/administração & dosagem , Fragmentos de Peptídeos/metabolismo , Ratos , Ratos Endogâmicos , Sermorelina , Distribuição TecidualRESUMO
The specific binding of vasoactive intestinal peptide (VIP) and the stimulatory effect of VIP upon cyclic AMP accumulation in isolated epithelial cells of rat ventral prostate were age dependent. The number of VIP receptors decreased but the efficiency of VIP on cyclic AMP accumulation increased in prostatic epithelium when considering the periods 35-65 days and 3-6 months. Since these features could be related to the known age-related decrease of androgen and androgen-receptor levels, we studied the effect of testosterone and its 5 alpha-reduced metabolite dihydrotestosterone upon both steps of VIP action. The two steroid hormones exerted a non-competitive inhibition on VIP-induced cyclic AMP accumulation but did not modify VIP binding to its specific receptors. This modulatory effect of androgens might involve their interaction with specific sites on the cell membrane leading to modifications of membrane activities including adenylate cyclase, as has been suggested by an increasing number of recent reports.
Assuntos
Envelhecimento , Androgênios/farmacologia , Próstata/metabolismo , Receptores dos Hormônios Gastrointestinais/metabolismo , Animais , AMP Cíclico/metabolismo , Di-Hidrotestosterona/farmacologia , Relação Dose-Resposta a Droga , Epitélio , Humanos , Masculino , Próstata/efeitos dos fármacos , Próstata/fisiologia , Ratos , Ratos Endogâmicos , Receptores dos Hormônios Gastrointestinais/efeitos dos fármacos , Receptores de Peptídeo Intestinal Vasoativo , Testosterona/farmacologia , Peptídeo Intestinal Vasoativo/metabolismoRESUMO
The effects of forskolin alone or in combination with vasoactive intestinal peptide (VIP) and the beta-adrenergic agonist isoproterenol on cyclic AMP accumulation in epithelial cells of rat ventral prostate were examined. Forskolin stimulated cyclic AMP in a time- and temperature-dependent manner. At 15 degrees C, forskolin behaved as a highly potent and relatively efficient stimulatory agent. The combination of forskolin with maximal doses of VIP or isoproterenol were purely additive. These results suggest that forskolin might act directly upon the catalytic subunit of adenylate cyclase in this particular class of cells.
