Effect of glycine and glucagon on glomerular filtration and renal metabolic rates

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Abstract
A rise in glomerular filtration rate (GFR) during saline infusion increases outer medullary more than cortical metabolic rate. To determine whether other GFR-increasing agents have a similar effect, renal metabolic rates were estimated by the heat-production technique during infusion of glycine or glucagon. Glycine and glucagon increased GFR by 17 +/- 2 and 32 +/- 2%, renal blood flow (RBF) by 34 and 21%, and outer medullary metabolic rate by 42 +/- 3 and 59 +/- 4%, respectively. Cortical metabolic rate rose by 7 +/- 1% during glucagon, and it increased by 29 +/- 2% during glycine infusion, suggesting a stimulation unrelated to sodium reabsorption. To determine whether glucagon influenced renal metabolism independent of its GFR-increasing effects, vasodilation was achieved by ureteral or suprarenal aortic constriction. Glucagon was without effect on RBF, GFR, and metabolic rate, but infusion of acetylcholine still raised RBF. We conclude that glucagon increases GFR by dilating vascular segments participating in autoregulation, and that energy-requiring NaCl reabsorption in the outer medulla is increased secondary to increased delivery of NaCl.

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