Purinergic signalling to rat ovarian smooth muscle: Changes in P2X receptor expression during pregnancy

The expression of P2X and P2Y receptor subtypes in the smooth muscle of the rat ovary during the oestrus cycle and pregnancy was examined using immunohistochemistry. RT-PCR studies of P2X receptor mRNA were also carried out. In the non-pregnant rats, P2X(2) receptor protein was dominant in the smooth muscle of perifollicular rings and blood vessels. P2X(1) protein expression was seen on vascular smooth muscle too, but little, if any, was present on perifollicular smooth muscle. No changes in P2X(1) or P2X(2) receptor expression were seen during the oestrous cycle. During early and mid-late pregnancy, there was a switch from P2X(2) to P2X(1) receptor protein expression in the smooth muscle of the perifollicular ring; P2X(1) receptors were also more prominently expressed than P2X(2) receptors on ovarian vascular smooth muscle in non-pregnant animals, but during late pregnancy the expression of P2X(2) receptors was found to equal that of the P2X(1) receptors. There was a return to non-pregnant P2 receptor subtype distribution 2 days after birth. Ovarian vascular and perifollicular smooth muscle showed immunoreactivity for P2Y(1), but not for P2X(3-7), P2Y(2) or P2Y(4) receptors. P2Y(1) receptor expression in ovarian smooth muscle of both blood vessels and follicular rings did not show significant changes during the oestrus cycle or pregnancy. RT-PCR studies indicated that P2X(1) and P2X(2) receptor mRNA was present in the ovary during pregnant and non-pregnant conditions. P2X(4-6) receptor mRNA was also present in all stages studied, however no immunostaining showing receptor protein for these subtypes was seen on the ovarian sections examined. In summary, purinergic signalling to ovarian perifollicular smooth muscle changed from P2X(2) to P2X(1) receptors during pregnancy, while there was an increase in P2X(2) receptor expression on vascular smooth muscle. Copyright (C) 2004 S. Karger AG, Basel.