Plasma insulin levels and beta-adrenoceptor antagonists. The effects of cardioselective and non-cardioselective beta-adrenoceptor antagonists with and without intrinsic sympathomimetic activity on basal insulin level and insulin level after glucose stimulation in normoglycemic dogs

Abstract

The effect of beta-adrenoceptor antagonists on the intravenous glucose tolerance test was investigated in conscious dogs. dl-Celiprolol (cardioselective with ISA = intrinsic sympathomimetic activity) 200 and 1000 microgram/kg i.v., dl-metoprolol (cardio-selective without ISA) 200 and 1000 microgram/kg i.v., dl-pindolol (non-selective with ISA) 5 and 25 microgram i.v. and l-bupranolol (non-selective without ISA) 10 and 50 microgram/kg i.v. were used in the study. The influence of beta-adrenoceptor antagonists on the plasma glucose and immunoreactive insulin following intravenous glucose tolerance test were evaluated by calculating the respective areas under the plasma curve. The present investigation clearly demonstrates the marked difference between the various beta-adrenoceptor antagonists on heart rate and, especially on metabolic parameters. dl-Metoprolol, a beta-adrenoceptor antagonist with cardioselectivity and without ISA can be assumed not to alter plasma insulin level and glucose assimilation. l-Bupranolol, a non-selective beta-adrenoceptor antagonist without ISA reduces plasma insulin level and probably enhances peripheral glucose uptake, resulting in an "unchanged" glucose tolerance. dl-Celiprolol or dl-pindolol, beta-adrenoceptor antagonists with ISA, but cardioselective or non-selective enhance both, basal insulin level and insulin level after glucose stimulation but must be assumed to decrease peripheral glucose uptake since here too glucose tolerance was unchanged.