EFFECT OF SINGLE NEONATAL VITAMIN-D-3 TREATMENT (HORMONAL IMPRINTING)ON THE BONE MINERALIZATION OF ADULT NON-TREATED AND DEXAMETHASONE-TREATED RATS

Hormonal imprinting (the first encounter between the hormone and recep tor after birth) is needed for the normal development of receptor. Pre sence of the appropriate hormone in excess, or its absence, as well as presence of hormone-like molecules able to bind to the maturing recep tor in this time, can cause faulty imprinting. In this experiment the effect of neonatal treatment with a single dose of 0.05 mg cholecalcif erol (vitamin D-3) was studied by bone densitometry. The treatment cau sed significant decrease of body weight in 3-month old females and als o significant reduction of bone mineral density (BMD) and bone mineral content (BMC) in males. Dexamethasone treatment of 3-month old rats f or 10 days increased BMD in males and BMC in females without affecting body weight. The double treatment (vitamin D neonatally and dexametha sone when adult) decreased the body weight of both sexes and increased BMD in males, and BMC, BMD/bw and BMC/bw in both sexes, related to th e control or the only vitamin D treated groups. Considering the hormon al imprinting effect of neonatal vitamin D treatment at glucocorticoid receptorial level in other experiments, similar effects also can be s upposed for vitamin D itself, manifested in the changes of bone minera lization.