Title : Rho A / Rho kinase : Human Umbilical Artery mRNA Expression in Normal 1 and Pre -

34 Pre-eclampsia represents a state of increased or prolonged vasoconstriction, partially 35 linked to the potent vasocontractile effect of isoprostanes. The process of Rho A– 36 mediated calcium sensitization is inherent to a state of prolonged contractility in many 37 smooth muscle types. The aims of this study were 1), to investigate mRNA expression 38 levels of Rho A and Rho kinase isoforms (I and II) in umbilical artery from 39 normotensive and pre-eclamptic women, and 2), to determine whether the effects of 40 two isoprostanes, 8-iso prostaglandin F2α (8-iso PGF2α) and 8-iso prostaglandin E2 (841 iso PGE2), on umbilical artery tone, were mediated via the Rho kinase pathway. Real42 time RT-PCR using primers for Rho A, ROCK I and ROCK II was performed on total 43 RNA isolated from umbilical artery specimens obtained from normotensive and pre44 eclamptic women. The effects of both isoprostanes (n=6) (in the absence and presence 45 of the specific Rho kinase inhibitor Y-27632), on umbilical artery tone were 46 measured, and compared with control recordings. Rho A mRNA expression levels 47 were significantly lower in umbilical artery samples obtained from pre-eclamptic 48 women (n=4) in comparison to those from normotensive women (n=6) (P<0.05). 49 ROCK I and ROCK II mRNA levels were similar in both vessel types (P>0.05). Both 50 isoprostanes exerted a significant concentration dependent vasocontractile effect 51 (n=7)(P<0.001) on umbilical artery. For 8-iso PGE2 this effect was antagonised by Y52 27632 (n=6) (P<0.01). The significant reduction of Rho A mRNA levels in umbilical 53 arteries from pregnancies complicated by pre-eclampsia may serve to counteract the 54 diminished perfusion associated with the pathophysiology of pre-eclampsia. The 55 vasocontractile effect of 8-iso PGE2 in pre eclampsia may in part be mediated via the 56 Rho kinase pathway. 57 58