Effects of (+/-) dobutamine and its (+) and (-) enantiomers in the isolated rat portal vein.

Employing the isolated rat portal vein for testing (+/-) dobutamine, and its (+) and (-) enantiomers, we have confirmed the results obtained by Ruffolo et al (1981, 1983) using different methods. In the rat portal vein, (-) dobutamine acts as an alpha agonist, less potent than noradrenaline. The racemate acts as an alpha-agonist with about half the potency of (-) dobutamine.

The isolated rat portal vein as a model for studying beta-adrenoreceptor agonists and antagonists.

1. The isolated rat portal vein was employed for essaying beta-agonists and beta-antagonists. beta-agonists elicit a log-dose dependent reduction of force of the spontaneous, rhythmic, myogenic contractions of the vein.

Beta-blocking actions of betaxolol on the isolated rat portal vein.

The characteristics of the beta-adrenoceptor population mediating the actions of noradrenaline and isoproterenol in the rat portal vein were examined in comparison with those in the rat atria. In the portal vein, the pA2 values obtained for the selective beta 1-adrenoceptor antagonist betaxolol were 100-fold lower than those obtained in the atria, suggesting that in the rat portal vein a population of beta 2-adrenoceptors is highly predominant.

No evidence of vascular dopamine receptors in the rat portal vein.

Dopamine (5.3 X 10(-6) to 5.3 X 10(-5) M) decreased the force of spontaneous myogenic contractions of the rat portal vein in a concentration-dependent manner in the presence of the alpha-adrenoreceptor antagonist BE-2254.