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 examin ed. After an 8-day control period, ewes received intravenous EGF at do ses of 0 (n = 6), 2 (low dose, n = 6), 10 (medium dose, n = 6), or 20 mug/h (high dose, n = 5) for 4 days. During EGF treatment, water intak e and urine volume increased (both P < 0.001) in a dose-related fashio n, although fluid balance was unaffected. Feed intake and fecal dry ma tter output were reduced (both P < 0.001) by the two higher doses of E GF. EGF had no effect on plasma potassium, sodium, or osmolality, but there was a dose-related natriuresis (P < 0.001). Treatment with EGF i ncreased plasma renin activity and aldosterone in the medium and high dose groups (both P < 0.001). Thus chronic intravenous infusion of 10- 20 mug EGF/h into sheep caused polydipsia, polyuria, and natriuresis w ith neutral fluid balance. Whether the resultant polydipsia or polyuri a was the primary response to EGF remains unclear.