Effects of β -adrenergic blockade on insulin-mediated glucose disposal in hypertensive and normotensive rats

OBJECTIVETo evaluate the impact of β-adrenergic blockade in spontaneously hypertensive rats (SHR)and in their normotensive controls, Wistar-Kyoto (WKY) rats, on whole-body glucose disposal under metabolic steady state conditions, in unrestrained and conscious animals. METHODSHR (n=13) and WKY rats (n=12) underwent a 240 min insulinaemic clamp study with or without a superinfusion (120th to 240th minutes; second step) of propranolol. RESULTSFrom 0 to 120 min (the first step) SHR showed significantly increased glucose uptake, muscle glycogen synthesis and glycogen synthase activity compared with WKY rats. When propranolol was superinfused, glucose uptake and muscle glycogen synthesis in SHR returned to levels similar to those observed in WKY rats during the first step. No significant differences were found for whole-body glycolysis in SHR and WKY in the first and second steps. CONCLUSIONHypertensive rats display an increased insulin sensitivity compared with controls. β-Blockade is associated with a reduction in overall glucose metabolism in SHR, but not in WKY rats.