Sexual dimorphism and testosterone effects on liver epidermal growth factor receptors in mice

A sexual dimorphism (M greater than F) for liver EGF receptor binding capacity has been observed in developing mice. To assess the aetiology of this sexual dimorphism we studied the effect of exogenous testosterone administration on liver EGF receptors in adult mice. In control animals the maximal binding capacity of liver EGF receptors in females was 57% of that in males. The affinity konstant (Ka) was 1.59 X 10(9) l/mol in females compared with 3.11 X 10(9) in males. Treatment with testosterone every second day for 14 days resulted in an increase in the binding capacity with 17% in males and 80% in females making the maximal binding capacity in females equal to that in untreated males. Receptor Ka was unchanged by treatment in males, but Ka in treated females was increased to the level of males (2.96 X 10(9) l/mol). These results indicate that the sexual dimorphism of hepatic EGF receptors involves receptor affinity and capacity; both are increased by testosterone in females.