Binding of radiolabelled luteinizing hormone to intact and ovariectomised rat uterus

Binding of ovine LH to uterine tissue preparation from intact and ovariectomised rat clearly indicates that uterus possesses specific binding sites for LH. Binding characteristics of LH to uterine tissue preparation from intact rat showed saturability with high affinity and low capacity. Scatchard plot analysis showed dissociation constant of the specific binding site to be 0.12 x 10(-9) mol/l and the number of binding sites was 2.31 +/- 0.05 f mol/mg protein. Ovariectomy did not change the binding affinity but effected a decrease in the number of binding sites (1.7 +/- 0.08 f mol/mg protein). LH treatment of ovariectomized (ovx) rat had no effect on binding affinity but significantly increased the number of binding sites (3.23 +/- 0.1 f mol/mg protein). Reduction of uterine weight due to ovariectomy and marked increase of ovx rat uterine weight by LH administration indicate a source of estrogen in ovx rat. An in vitro uterine tissue slice (from intact and ovx rat) incubation showed depletion of 17 beta-estradiol (E2) content in ovx rat which significantly elevated on LH addition. Data suggest that LH binding to rat uterine tissue has biological relevance.