Effects of Gestational Age and Labor on Expression of Prostanoid Receptor Genes in Baboon Uterus1

We determined the effect of gestational age and labor on the regional expression of prostanoid receptor genes in baboon myometrium. Cesarean hysterectomy was performed on 15 pregnant baboons of known gestational age in the last third of pregnancy, five of them during spontaneous term labor. Expression of prostanoid receptor genes was studied using Northern blot analysis. Transcripts of similar size to the human were detected for prostanoid EP(1), EP(2), EP(3), EP(4), IP, FP, and TP receptor genes using Northern blot analysis. There were no gestational age-related changes in expression of these genes. Expression of EP(1), EP(3), and IP receptor RNA mRNA was significantly higher in myometrium from the fundus (compared with the lower segment), whereas EP(2) gene expression was significantly lower in the fundus. Labor was associated with a reduction in the regional variation of both EP(2) and IP receptor gene expression, but not EP(1) and EP(3) expression. Labor was also associated with an overall lower level of expression of EP(2) receptor mRNA. We conclude that regional and labor-related variation in myometrial expression of prostanoid receptor genes may have a key role in primate parturition.