femoral bone mineral density and bone mineral content in bromocriptinetreated pregnant and lactating rats since hyperprolactinemia was found to induce osteopenia in the metaphysis of long bone in nonmated female rats pregnant and lactating rats with sustainedly high plasma prolactin prl levels might also exhibit some changes in their long bones we performed a longitudinal study in pregnant lactating and postweaning rats using dualenergy xray absorptiometry to demonstrate sitespecific changes ie metaphysis vs diaphysis in femoral bone mineral density bmd and content bmc the results showed that femoral metaphyseal bmd and bmc were higher when compared to their agematched controls during pregnancy before decreasing in late lactation and postweaning on the other hand femoral diaphyseal bmc increased during pregnancy early lactating and midlactating periods without change during late lactation and postweaning after 7 days of bromocriptine administration which inhibited endogenous prl secretion the lactationinduced increases in bmc during early and midlactating periods were abolished moreover a decrease in metaphyseal bmd during late lactation was restored to the control levels by bromocriptine however bromocriptine did not antagonize the pregnancyinduced increases in bmd and bmc it could be concluded that the effect of prl on bone was variable during the reproductive periods while having no effect on femoral bmd and bmc during pregnancy prl was responsible for bone gain in early and midlactating periods but induced bone loss during late lactating period