50 µg of shRNA plasmid were complexed with 8µl of in vivo-jetPEI (N/P=8) in a total volume of 600µl and injected into renal artery of rats after artery and vein were isolated and tied. Complexes were held for 4 minutes in the kidney before artery and vein were un tied.

Normal pregnancy is a state marked by avid sodium retention and plasma volume expansion. Insufficient plasma volume expansion results in the compromised maternal state of intrauterine growth restriction, which afflicts approximately 5% of all human pregnancies. We have recently shown that renal epithelial sodium channel (ENaC) activity in vivo in the late pregnant (LP) rat is increased. To determine the importance of the renal versus extrarenal ENaC in sodium retention and blood pressure regulation during pregnancy, we have chronically blocked the ENaC pharmacologically with daily subcutaneous injections of benzamil and genetically using intrarenal transfection of alphaENaC short hairpin RNA. Compared with untreated LP control animals, LP rats treated with benzamil retain less sodium and have reduced mean arterial blood pressure. Furthermore, LP rats treated with benzamil had lower maternal body weight gain. Intrarenal transfection of alphaENaC short hairpin RNA versus scrambled small RNA successfully decreased renal alphaENaC mRNA expression in LP rats. Intrarenal transfection of alphaENaC short hairpin RNA reduced maternal sodium retention, body weight gain and pup weight. Redundant physiological systems that protect blood pressure and sodium homeostasis were unable to compensate for the loss of ENaC activity in the pregnant rat. These findings demonstrate that the renal ENaC is necessary for maintaining pregnancy-mediated sodium retention, volume expansion and blood pressure regulation.