Epidermal growth factor (EGF) increases the renal amino acid transport capacity in amino acid loaded rats

In anaesthetized adult female rats, the influence of epidermal growth facto r (EGF) on renal amino acid handling was investigated in glutamine, arginin e (both 50 mg/100 g b.wt. per hour), or alanine (90 mg/100 g b.wt. per hour ) loaded animals. Continuous infusions of the three amino acids were follow ed by an increase in the fractional excretion (FE) of the administered amin o acids as well as of the other endogenous amino acids. Under load conditio ns (alanine, arginine or glutamine), EGF pretreatment (8 mu g/100 g b.wt. s ubcutaneously for 8 days, twice daily 8 a.m. and 4 p.m.) was followed by a stimulation of renal amino acid reabsorption. The increase in the fractiona l excretion of the administered amino acids was significantly lower than in non-EGF-treated rats. These changes in amino acid transport were connected with a significant reduction of GFR after EGF pretreatment (0.96 +/- 0.10 vs. 0.62 +/- 0.07 ml/min x 100 g b.wt.) and a distinct increase in sodium e xcretion (2.98 +/- 0.55 vs. 4.97 +/- 0.71 mu val/100 g b.wt. x 20 min). Aft er loading with p-aminohippurate (PAH; 200 mg/100 g b.wt.), PAH excretion i n EGF rats was increased by about 20%, whereas urinary protein excretion wa s lower in EGF pretreated rats (control: 0.45 +/- 0.04 vs. EGF: 0.18 +/- 0. 03 mg/100 g b.wt. x 20 min). The PAH load reduced amino acid reabsorption a s a sign of overloading of renal tubular transport capacity, but in EGF pre treated animals the amino acid excretion was only slightly increased under these conditions. Furthermore, EGF pretreatment depressed normal kidney wei ght gain significantly (874 +/- 18 vs. 775 +/- 32 mg/100 g b.wt.). EGF can improve the renal tubular transport capacity, but, compared to well-known s timulators of renal transport like dexamethasone or triiodothyronine, its e ffect is only of a moderate degree.