Direct involvement of luteinizing hormone in uterine function

The effect of bovine LH on bovine uterine tissue from three phases of the o estrous cycle was studied. It was found that in the luteal phase the endome trium, myometrium and cervix contain a LH receptor (LH-R) mRNA transcript a nd the 93 kDa receptor protein. Both LH-R protein and its mRNA were also fo und in the uterine vein but mainly at pre-oestus/oestrus. Incubation of cer vical minces from the luteal phase with LH significantly increased (p < 0.0 5) the intracellular cAMP, inositol phosphate and cyclooxygenase as well as the production of PGE(2) but not PGF(2 alpha). Induction of endometrial cy clooxygenase by LH is associated with release of PGF(2 alpha) in the late l uteal phase and 2 to 4 days postovulation. In contrast, in the pre-oestrous /oestrous uterine vein, the signal for the transcript for LH-R and the LH-R protein was significantly higher than at other stages of the cycle. Incuba tion of uterine vein minces from pre-oestrus/oestrus with LH significantly increased intracellular concentration of cyclooxygenase as well as producti on of both PGE(2) and PGF(2 alpha). The presence of physiologically active LH-R in the uterine tissue suggests a direct involvement of LH in uterine f unction, i.e. uterine relaxation by cAMP and PGE, and regression of the cor pus luteum by uterine PGF(2 alpha).