A NEW APPROACH FOR INVESTIGATING HYPOTHALAMO-PITUITARY-GONADAL AND ADRENAL FEEDBACK CONTROL MECHANISMS: ACTIVE IMMUNIZATION WITH STEROIDS

ABSTRACT A new method for the investigation of hypothalamo-pituitary-gonadal and adrenal feedback control mechanisms based on the biological neutralization of gonadal and adrenal steroids by active immunization is proposed. The regulatory influence of a given steroid in the feedback control is proved when reduction of the free, biologically active fraction of this steroid caused by antibody binding induces a positive response of the pituitary, thus effecting gonadal or adrenal hypertrophy and hyperfunction. The advantages and limitations of the new model are demonstrated by the effects of active immunization of rabbits with cortisol (F), aldosterone (Aldo), dehydroepiandrosterone (DHA), androstenedione (Δ4-A), testosterone (T), 5α-dihydrotestosterone (5α-DHT), 5β-DHT and oestradiol (E2). In the immunized animals and in a control group serum concentrations of total corticosteroids (TC), DHA, T, Δ4-A, E1, E2, LH and FSH, the percentage of binding of steroids in serum and the specificity of the antisera are determined. The testes are evaluated by histometry and the nuclear volume of the adrenocortical and Leydig cells is measured.