EFFECT OF RETINOID (VITAMIN-A OR RETINOIC ACID) TREATMENT (HORMONAL IMPRINTING) THROUGH BREAST-MILK ON THE GLUCOCORTICOID RECEPTOR AND ESTROGEN-RECEPTOR BINDING-CAPACITY OF THE ADULT-RAT OFFSPRING

Hormonal imprinting occurs perinatally when the developing receptor an d the appropriate hormone meet each other. The presence of related mol ecules in this critical period causes misimprinting. Ligands bound to a member of the steroid-thyroid receptor superfamily can disturb the n ormal maturation of other members of the family, which is manifested i n altered binding capacity of the receptor and decreased or increased response of the receptor-hearing cell for life. Excess or absence of t he hormone also can cause misimprinting. Treatments once a week for 3 weeks of nursing rat mothers with 6 mg/animal all-trans retinol/dose c aused faulty imprinting manifested in significantly reduced density (B max) of thymic glucocorticoid receptor in male and female adult progen ies alike. 0.03 mg all-trans retinoic acid treatment of nursing mother s was ineffective. Receptor affinity (K-d) was Unchanged in both cases as well, as the binding values of uterine estrogen receptors. The res ults of the experiment call attention to the transmission of imprinter molecules by breastmilk to the progenies, which can cause lifelong al terations at receptorial level and points to the human health aspect. Possible reasons for the differences between retinol and retinoic acid effects and in the sensitivity of receptors are discussed.