Identification of an androgen receptor within the uterus of the domestic fowl

Cytosolic and nuclear fractions of the uterus (shell gland) of the hen's ov iduct were found to contain a specific [17 alpha-methyl-H-3] -methyltrienol one ([H-3]R1881; a synthetic androgen) binding component having properties of an androgen receptor; i.e., binding specificity, high affinity, and limi ted capacity. The value of the equilibrium dissociation constant (K-d) was of the order of 10(-9), and did not differ between laying and nonlaying hen s. The maximum binding capacity (B-max) per gram of tissue of both fraction s was greater in laying hens than in nonlaying hens. When 5 alpha-dihydrote stosterone was administered exogenously, the B-max of the cytosolic fractio n decreased and that of the nuclear fraction increased without any change i n Kd. The specific binding in both fractions was at an increased level from 4 to 11 h before oviposition, suggesting that androgen binding may be rela ted to certain events during an early stage of shell formation in the uteru s of laying hens.