Acute effect of prolactin on bone⁴⁵Ca accumulation in rats

Abstract

In an attempt to evaluate the acute effect of PRL on bone turnover, experiments were performed in sexually mature female Wistar rats which were given an intraperitoneal (ip) administration of 1.25 mM CaCl2solution containing 6 μCi45Ca. Dose response study showed a two fold higher rate of45Ca uptake in 30 min by control trabecular bones (sternum and vertebrae 5-6) compared with control compact bones (femur and tibia). Femur exhibited a dose dependent increase in45Ca uptake in response to pharmacological doses of 0.01 and 0.02 mg PRL/100 g body weight but was less responsive to 0.04 mg PRL/100 g body weight. Tibia only responded with increased45Ca uptake to 0.02 and 0.04 mg PRL/100 g body weight while trabecular bones were unresponsive. By varying the intervals between administration of45Ca (0 min) and PRL (0, 30 or 60 min) and bone harvesting (30, 60 or 90 min), it was found that 0.01 mg PRL/100 g body weight had a biphasic action on45Ca movement. It initially enhanced45Ca influx into femur by 30 min followed by an accelerated45Ca efflux from femur back to the circulation. It could be concluded that PRL acutely stimulated calcium turnover in compact bone.