Uterine Uptake of Progesterone and Estradiol in Young and Aged Rabbits

Summary

Eighteen young female rabbits 6-13 mo old, and 28 aged rabbits 49-72 mo old, were randomized into three treatment groups. Group 1 does were ovariectomized and sacrificed 14 days later. Groups 2 and 3 were sacrificed 12 and 24 days post-coitum (pc), respectively. Net progesterone-7-³H and 17β-estradiol-4-¹⁴C uptakes were determined for uterine tissue strips incubated at 37° for 0, 2 and 4 hr by correcting for skeletal muscle incubated similarly.

Net uterine uptakes of progesterone-7-³H and 17β-estradiol-4-¹⁴C were greatest in the ovariectomized does and decreased particularly in the young does with increased time pc. Of most significance was the two- to fourfold greater uptake of both steroid hormones by uteri from young does than old does after 2 and 4 hr of incubation in the ovariectomized group and after 4 hr of incubation in the 12 day pc group. By 24 days pc steroid hormone uptake was low in both groups and not significantly different. The reduced capacity of uterine tissue in aged rabbits to take up steroid hormones is interpreted to be one of the uterine factors limiting reproductive performance in aged does.

We thank Dr. James D. McCaffree for help in the statistical analysis and Miss Gloria Shawver for assistance in preparing the manuscript.