comparative study on the effect of bisoprolol and other beta-blockers on the counter-regulation of insulin-induced hypoglycaemia in the rat

ABSTRACT

The effect of bisoprolol, a new selective beta 1 adrenoreceptor blocker, on the counter-regulation of insulin-induced hypoglycemia [IIH] was studied and compared to the effect of propranolol and atenolol. Results showed that the pretreatment of rats with either of the three beta-blockers, propranolol [30 mg/kg], atenolol [50 mg/kg] or bisoprolol [10 mg/kg], for seven consecutive days did not affect plasma glucose nadir at 30 and 60 minutes after insulin injection [1 U/kg, s.c.]. However, the glucose recovery rate measured at 120 minutes, was significantly reduced by propranolol and bisoprolol, but not atenolol. Similarly the rebound of free fatty acid [FFA] in response to insulin was significantly attenuated by propranolol and bisoprolol, whereas atenolol only reduced it. The rise in plasma corticosterone level measured at 30 and 60 minutes from IIH was significantly lowered by propranolol and bisoprolol, while no significant effect was observed with atenolol pretreatment. Insulin-induced depletion in plasma c-AMP levels were significantly potentiated by the pretreatment of rats with the three beta-blockers studied. However, at 120 minutes all the three alpha-blockers significantly prevented insulin-induced depletion in plasma c-AMP. Results presented indicated that bisoprolol showed less selectivity than atenolol at least in respect to glucose metabolism