HUMAN CORTICOTROPIN-RELEASING HORMONE-RECEPTOR - DIFFERENCES IN SUBTYPE EXPRESSION BETWEEN PREGNANT AND NONPREGNANT MYOMETRIA

There is increasing evidence that CRH, which is the principal neuroreg ulator of the hypothalamic-pituitary-adrenocortical axis, is also invo lved in the mechanism of human labor. The human myometrium has been sh own to express several high affinity CRH receptors, although the ident ities of the CRH receptor subtypes have yet to be identified. To inves tigate further the expression of the CRH receptor in human myometrium, we used RT-PCR, fluorescent in, situ hybridization and immunofluoresc ence to identify and localize the four subtypes, 1 alpha, 1 beta, 2 al pha, and the variant C, of the CRH receptor. Interestingly, the CRH re ceptor subtypes in myometrium exhibit differential expression patterns ; in human pregnant myometrium at term all four receptor-subtypes were expressed, whereas only the 1 alpha-and 1 beta-receptor subtypes were found in the nonpregnant myometrium. This would suggest that CRH, act ing via different receptor subtypes, is able to exert different action s on the myometrium in the pregnant state compared to the nonpregnant state. Furthermore, in the pregnant human uterus, CRH receptors were l ocalized in both smooth muscle and fibroblasts. These findings suggest that CRH receptor expression plays an important modulatory role in my ometrial and possibly in cervical function.