UP-REGULATION IN LATE PREGNANCY OF BOTH G(01)ALPHA AND G(02)ALPHA ISOFORMS IN HUMAN MYOMETRIUM

The nature of the 39 kDa pertussis toxin substrate previously detected in human pregnant myometrium was investigated. Comparison of membrane s from non-pregnant and from 39-40 week pregnant myometrium revealed a higher level at 39 kDa of pertussis toxin ADP-ribosylation and G(o) a lpha immunoreactivity in late pregnancy. Furthermore, quantification o f both G cu isoforms with specific anti-alpha(o1)- and alpha(o2)-antib odies revealed an increase in their expression in late pregnancy. At t he same time, only limited changes in the levels of G(i1,2), G(i3) and G(q) were observed. In rat myometrial membranes, neither pertussis to xin substrate nor G,cr immunoreactivity could be detected at the 39 kD a level. These results demonstrate that, in the human myometrium in la te pregnancy, there is an increase in the expression of both isoforms of the G(o) alpha subunits, suggesting a role for these proteins throu ghout gestation and/or near term for parturition.