Glucose stimulates renin secretion via adrenergic mechanisms in the rat

To elucidate whether and why glucose directly influences renin secretion, the effect of glucose on renin secretion was investigated in the rat. In an in vivo study, renin activity significantly (p<0.01) increased from the basal value of 7.6 +/- 1.4 to 14.2 +/- 3.2 ng Ang I/ml/hr (mean +/- SD) after intravenous glucose (1.0 g/kg, in 50% glucose solution ) injection. Propranolol (10.5 mg/kg) pretreatment partly abolished the increase in renin activity induced by glucose injection. In an in vitro study, the isolated kidneys of male Wistar rats (200-250 g) were perfused with a basal perfusing medium containing 5.5 mM glucose for 20 min, and then perfused with the medium containing 16.5 mM glucose, 27.5 mM glucose, 5.5 mM glucose + 22 mM mannitol, 27.5 mM glucose + 1 microM phentolamine, or 27.5 mM glucose + 1 microM propranolol for 10 min, respectively. Renin activity was significantly increased from a basal value of 8.1 +/- 4.5 to peak value of 17.9 +/- 3.0 ng Ang I/ml/hr (p<0.01) by 16.5 mM glucose, to 59.0 +/- 10.5 ng Ang I/ml/hr (p<0.005) by 27.5 mM glucose, and to 24.7 +/- 5.8 ng Ang I/ml/hr (p<0.01) by 5.5 mM glucose + 22 mM mannitol. The increase in renin activity in the kidney perfused with 27.5 mM glucose was significantly (p<0.005) higher than that with 16.5 mM glucose or that with 5.5 mM glucose + 22 mM mannitol. The 27.5 mM glucose-stimulated increase in renin activity was not changed by the addition of 1 microM phentolamine, while it was completely abolished by the addition of 1 microM propranolol. These results suggest that glucose has a direct stimulating effect on renin secretion probably through beta-adrenergic mechanisms in the rat.