Hormonal, fluid, and electrolyte responses of sheep during chronic intravenous infusion of epidermal growth factor

Epidermal growth factor (EGF) has been shown to increase water intake and urine volume. To further characterize these responses the effects of EGF on fluid balance, electrolyte, and hormone profiles were examined. After an 8- day control period, ewes received intravenous EGF at doses of 0 (n = 6), 2 (low dose, n = 6), 10 (medium dose, n = 6), or 20 μg/h (high dose, n = 5) for 4 days. During EGF treatment, water intake and urine volume increased (both P < 0.001) in a dose-related fashion, although fluid balance was unaffected. Feed intake and fecal dry matter output were reduced (both P < 0.001) by the two higher doses of EGF. EGF had no effect on plasma potassium, sodium, or osmolality, but there was a dose-related natriuresis (P < 0.001). Treatment with EGF increased plasma renin activity and aldosterone in the medium and high dose groups (both P < 0.001). Thus chronic intravenous infusion of 10-20 μg EGF/h into sheep caused polydipsia, polyuria, and natriuresis with neutral fluid balance. Whether the resultant polydipsia or polyuria was the primary response to EGF remains unclear.