MECHANISM OF GLOMERULAR HYPERFILTRATION AFTER A PROTEIN MEAL IN HUMANS - ROLE OF HORMONES AND AMINO-ACIDS

OBJECTIVES - Previous studies demonstrated that protein meals and amin o acid (AA) infusions increase glomerular filtration rate (GFR) and re nal plasma flow (RPF) and that somatostatin (SRIH) infusion inhibits t hese increments. We tested whether a single AA such as alanine could i ncrease GFR and RPF and whether the changes in GFR and RPF could be ex plained on the basis of changes in glucagon, growth hormone (GH), and insulin. RESEARCH DESIGN AND METHODS - In the first experiment, alanin e was infused with or without SRIH in five normal subjects. In the sec ond experiment, five other subjects were infused with SRIH on three se parate occasions. In a control study, insulin, glucagon, and GH were g iven at replacement doses; in a hyperglucagonemia study, glucagon was given at a rate of 0.2 mu g . kg(-1) . h(-1) (hypoglucagonemia); and i n a high GH study, GH was given at a rate of 2 mu g . kg(-1) . h(-1). GFR and RPF were measured using inulin and para-aminohippurate, respec tively. RESULTS - Alanine increased GFR and RPF, whereas SRIH inhibite d these changes (P < 0.05). Hyperglucagonemia or high GH with or witho ut insulin failed to increase RPF or GFR. CONCLUSIONS - A single AA su ch as alanine increases GFR and RPF, and this increase is dependent on a factor inhibited by SRIH. Although GH, glucagon, and insulin are fa ctors inhibited by SRIH, none of these factors explains the changes in RPF: and GFR in our acute studies.