Plasma concentrations and urinary excretion of mouse epidermal growth factor associated with the inhibition of food consumption and of wool growth in Merino wethers

Abstract

Twenty-four adult Merino wethers were given mouse epidermal growth factor (mEGF) subcutaneously at doses ranging from 0.02 to 0.12 mg/kg body weight or intravenously in the dose range 0.10 to 0.14 mg/kg body weight for periods ranging from 3 to 48 h. Plasma concentrations of mEGF were measured by radioimmunoassay and effects of treatment on food consumption and wool growth were observed. Plasma concentrations of the protein sustained for 15-24 h at about 20 ng mEGF/ml (or exceeding this) almost invariably caused feed rejection and casting of the fleeces. This last result clearly indicated disruption of proliferative activity among the replicating cells in wool follicles which regulate wool growth. The inhibitory effects on appetite and wool growth of smaller doses of the protein and of plasma concentrations equal to those above which were sustained for shorter periods have also been examined. Approximately 10% of the dose of mEGF appeared in the urine of three sheep 1 to 3 days after the start of s.c. infusions of 5 mg for 7 h.