| The aim of this study was to characterize the expression and regulation of the genes encoding gap junction proteins, connexins, in the rat uterus throughout late gestation. Using a PCR-based technique with primers specific for various connexin cDNA sequences, positive amplification products were found for Cxs-43, 26, 37 and 40 in the rodent myometrium at the time of labour, but not Cxs-32, 46, and 31. Subsequent Northern analysis revealed a high abundance of the Cx-26 transcripts in pregnant rat myometrium. More interestingly, Cx-26 was found to exhibit a distinct temporal expression pattern from Cx-43. In contrast to Cx-43 whose expression is low throughout pregnancy but increases immediately before the onset of labour (day 23), expression of Cx-26 increases on day 17, reaches maximal levels between days 19 and 21 and falls to low levels prior to the onset of labour. Treatment of pregnant rats with progesterone (P) beginning on day 20 (which blocks both the increase in Cx-43 expression and the onset of labour) maintains the elevated expression of Cx-26. Induction of preterm labour in rats following ovariectomy (OVX) on day 17 inhibits the normal increase in Cx-26 transcripts (while significantly increasing Cx-43 levels). P treatment to these animals reverses the effects of OVX. Thus, it appears that Cx-26 and Cx-43 are differentially modulated by these steroid hormones, so that P enhances Cx-26 while inhibiting Cx-43 expression. These data suggest that there are multiple connexins expressed in the myometrium and that complex regulatory mechanisms operate to generate differential expression patterns during pregnancy. |
