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 glucoseinjection. In an in vitro study, the isolated kidneys of male Wistar rats (200–250g) were perfused with a basal perfusing medium containing 5.5mM glucose for 20 min, and then perfused with the medium containing 16.5mM glucose, 27.5mM glucose, 5.5mM glucose + 22mM mannitol, 27.5mM glucose + 1 μ M phentolamine, or 27.5mM glucose + 1 μ M propranolol for 10min, 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 16.5mM glucose, to 59.0 ± 10.5 ng Ang I/ml/hr (p < 0.005) by 27.5mM glucose, and to 24.7 ± 5.8 ng Ang I/ml/hr (p < 0.01) by 5.5mM glucose + 22mM mannitol. The increase in renin activity in the kidney perfused with 27.5mM glucose was significantly (p < 0.005) higher than that with 16.5mM glucose or that with 5.5mM glucose + 22mM mannitol. The 27.5mM glucose-stimulated increase in renin activity was not changed by the addition of 1 μ M phentolamine, while it was completely abolished by the addition of 1 μ M propranolol. These results suggest that glucose has a direct stimulating effect on renin secretion probably through β -adrenergic mechanisms in the rat.