Estudo do efeito da dobutamina (Dobutrex) R e da radiação laser sobre a ação hidrosmotica da vasopressina em bexiga de sapo "in vitro"

AUTOR(ES)
DATA DE PUBLICAÇÃO

1991

RESUMO

In the present work the effects of several pharmacological agents in special Dobutamine and a physical agent-Laser radiation - on the events that follow the interaction of Vasopressin with membrane receptors related to syn¬thesis and inactivation of cyclic-AMP in the toad bladder, are described and characterized. Water flow across the membrane was measured gravimetrically by the technique of BENTLEY(1958) in sac preparations of the membrane, and by the technique of PROCÓPIO &: LACAZ VIEIRA (1977) in sheet preparations of the bladder. Dobutamine or the application of Laser radiation did not al¬ter the normal water permeability of the epithelium in the absence of Vaso¬pressin. In contrast, adrenoceptors activation by Dobutamine (8x10-4M) led to a significant (about 31%) blockage of the hydrosmotic action of Vasopressin. Similarly, low-energy Laser radiation (10/ Jcm2) blocked the tissue response to Vasopressin after the previously treatment of the membrane with the hor¬mone. This inhibitory effect was not observed when the mucosal face of the membrane was exposed to the Laser radiation. On the other hand, association of cyclic-AMP with Laser radiation pro¬moted an increase in the water flow suggesting that the physical agent may present dual effects on the water tran-sport, one being negative on the cyclic¬AMP production by the adenylate-cyclase complex and the other being positi ve on the nucleotide action by phosphodiesterase - nucleotide inhibition. It was also seen that Theophylline - the phosphodiesterase inhibitor ¬stimulated water transport by increasing cyclic-AMP concentration in the tis¬sue. The association of Dobutamine with Theophylline led to a decrease in the methyl-xanthine hydrosmotic activity, being this effect restored almost com¬pletely by the presence in the serosal bathing solution of an alpha-adrenergic antagonist, Phentolamine. These results suggest that Theophylline acts not only by blocking phosphodiesterase activity, but also by stimulating adenylate¬cyclase-dependent complex in the conversion mechanism of ATP to cyclic-AMP. In constrast, when Dobutamine, Vasopressin and an beta-adrenergic an¬tagonist, Propranolol were associated, the hydrosmotic response of the tissue to Vasopressin was not restored. On the other hand, the association of alfa¬adrenergic agent Phentolamine or Rauwolscine to the Dobutamine and Vaso¬pressin serosal bathing solution restored the action of Vasopressin, evidencing alpha2-adrenergic receptor participation on the blockage of the hydrosmotic action of the hormone, further characterizing this receptor as one diuresis ag¬onist. The results obtained by the association of Indomethacin with Laser ra¬diation before and after the stimulation of water flow by Vasopressin point to the possibility that Laser radiation would stimulate Prostaglandins syn¬thesis in this tissue, interfering in this way with the hydrosmotic activity of Vasopressim

ASSUNTO(S)

radiação osmose

ACESSO AO ARTIGO

Documentos Relacionados