[A study on the renal action of beta 1- and beta 2-adrenoceptors in rats]

The present experiments were designed to study urine volume and urinary sodium excretion effects of beta-antagonists and beta-agonists with reference to beta 1- and beta 2-adrenoceptors in rats. The beta-antagonists used were atenolol as a selective beta 1-antagonist, butoxamine as a beta 2-antagonist and propranolol as a non-selective beta-antagonist. The beta-agonist used were salbutamol as a beta 2-agonist and isoproterenol as a non-selective beta-agonist. Beta-antagonists increased the urine volume and urinary sodium excretion, but beta-agonists decreased the urine volume and urinary sodium excretion. With regards to these effects, atenolol increased the urine volume more than urinary sodium excretion, isoproterenol decreased the urine volume more than urinary sodium excretion, and salbutamol decreased the urinary sodium excretion more than urine volume. When beta-antagonists were infused with a beta-agonist, the original diuretic effects of these beta-antagonists were inhibited by the beta-agonist. In these effects, beta-antagonists infused with isoproterenol inhibited urine volume more than urinary sodium excretion, but beta-antagonists infused with salbutamol inhibited urinary sodium excretion more than urine volume. These results indicate that the urine volume is related to beta 1-adrenoceptors, while the urinary sodium excretion is related to beta 2-adrenoceptors, although there is no selectivity towards either beta 1-adrenoceptors or beta 2-adrenoceptors as far as diuresis or antidiuresis is concerned.