Maturation of 17 beta-estradiol binding protein in the hypothalamus and anterior pituitary of male rats.

Levels of estrogen binding proteins in the cytosol of hypothalamic and pituitary tissue of male rats at different ages were estimated. Two classes of estrogen binding sites were detected in 13 and 20 days old animals. The number of high affinity estrogen binding sites (K = ca. 2 x 10(-10) mol) of the hypothalamus was slightly larger in 13 days old animals, then decreased to constant levels at the age of 20 days and no changes were observed thereafter. Levels of low affinity binding sites of the hypothalamus (K = ca. 5 x 10(-9) mol) decreased with age and were no longer detectable in 30 days old animals. Similarly, a decrease of low affinity estrogen binding sites with age was recorded for pituitary cytosol samples and this class of receptor sites was no longer observable in 30 days old male rat. At 13 days high levels of high affinity 17 beta-estradiol binding protein was registered and minimal numbers of binding sites were found at 20, 30 and 40 days. Thereafter, the levels remained constant until 100 days and were similar to values observed in the 13 days old male animals. Apparent affinity constants of two classes of binding sites in hypothalamus and pituitary were similar...