Effects of beta-adrenergic blockade or stimulation on net rate of hydrothorax absorption

We determined in anesthetised rabbits the net rate of liquid absorption (NRLA) from Ringer or 1% albumin-Ringer hydrothoraces with the beta-blocker propranolol (or nadolol) or the beta-agonist terbutaline. The beta-blocker reduced NRLA by 38% in 2 ml Ringer hydrothoraces, and did not change it in 2 ml albumin-Ringer hydrothoraces; hence, with beta-blocker NRLA became similar in both kinds of hydrothorax (0.31 +/- 0.02 ml/h). Terbutaline decreased NRLA by 25% in 2 ml Ringer hydrothoraces, and increased it by 29% in 2 ml albumin-Ringer hydrothoraces; hence, with terbutaline NRLA became similar in both kinds of hydrothorax (0.40 +/- 0.02 ml/h), and 25% higher than with beta-blocker. Because beta-adrenoreceptor activity inhibits lymphatic smooth muscles and may increase Na+ transport in epithelia, these results suggest that: (1) pleural mesothelium is provided with beta-receptors, which increase Na+ transport and seem activated by protein dilution, (2) beta-receptors of the pleural lymphatics are essentially silent with and without protein dilution, (3) the lymphatic drainage produced by smooth muscle activity is smaller than the increase in solute-coupled liquid absorption caused by mesothelium beta-receptors.