Quantification of Receptors for Estradiol-17 beta and progesterone in the pituitary and hypothalamus of gilts during prepubertal development.

To determine whether pituitary receptors for estradiol-17 beta (E217beta) and progesterone (P4) change during prepubertal development, receptors were quantified by nuclear and cytoplasmic exchange assays from Yorkshire gilts 1, 2.5, 4, and 5.5 months old. No significant differences in the concentration of cytoplasmic or nuclear E217beta receptors were found during these prepubertal ages. Likewise, no differences in the concentration of cytoplasmic or nuclear P4 receptors were found during the four ages tested. These results suggest that prepubertal gilts approach the onset of puberty without a significant change in the concentration of E217beta or P4 receptors in the pituitary gland. To determine whether hypothalamic receptors for E217beta or P4 change during prepubertal development, receptors were quantified in hypothalami removed from these same gilts. At 2.5 months of age, the concentration of E217beta receptors was less (P less than 0.01), but the physiological significance of this reduction is unclear. No significant differences in the number of hypothalamic nuclear E217beta receptors were found during these prepubertal ages. Likewise, no differences in the concentration of cytoplasmic or nuclear P4 receptors were found during the four ages tested. These results suggest that prepubertal gilts approach the onset of puberty without an increase in the concentration of E217beta or P4 receptors in the hypothalamus.