LACK OF INFLUENCE OF SHORT-TERM TREATMENT WITH PROPRANOLOL AND TERBUTALINE ON METABOLISM AND ENERGY-EXPENDITURE OF THE NA-K PUMP IN HUMAN ERYTHROCYTES EVALUATED BY MICROCALORIMETRY

A double blind placebo-controlled study was conducted of the effects o f oral propranolol (beta1beta2-adrenoceptor antagonist) and terbutalin e (beta2-adrenoceptor agonist) on erythrocyte heat production, measure d by direct microcalorimetry under static conditions at 37-degrees-C a nd pH 7.4. Propranolol 80 mg and terbutaline slow-release 7.5 mg were randomly administered twice daily for one week to 15 healthy males, us ing a cross-over design. No thermogenic difference was detected. Serum potassium was significantly decreased by terbutaline but was only sli ghtly increased by propranolol, but no relationship was found between changes in the extra- and intracellular levels. In the placebo group, 10% of total cell energy was consumed by the Na-K pump, as assessed by ouabain inhibition, and this value was not significantly affected by the treatments. Thus, it seems unlikely that there is a clinically rel evant influence on the Na-K pump in erythrocytes during continuous ter butaline or propranolol medication. It is concluded that short term me dication with propranolol and terbutaline in therapeutic doses has alm ost no thermal or metabolic effect on human erythrocytes. The results indirectly imply that no clinically relevant beta-adrenoceptor effects are mediated in erythrocytes and this may also be true with regard to the 'membrane effect' of propranolol.