Abstract:
The aim of the study was to determine the amount of angiotensinogen expressionand its protein product in fetal sheep liver and kidney in the last third ofgestation. Angiotensinogen mRNA was measured by RNase protection assay and itsprotein levels were measured by radioimmunoassay. Levels were measured at 80,95, 111, 125 and 139 days. Angiotensinogen mRNA was present in all fetal liverand kidney samples tested. The ratio of hepatic angiotensinogen mRNA/18 SrRNA increased by 100% (P<0.001) andangiotensinogen levels increased by 33%(P<0.001) in fetal sheep from 80 to 139 d. Over thesame period the ratio of renal angiotensinogen mRNA/18 S rRNA increased by170% (P<0.001) and renal angiotensinogenprotein increased by 41% (P<0.001). The levelsof angiotensinogen mRNA and its protein in the adult kidney were less than inkidneys of 139 d old fetuses (P<0.01). There was adirect relationship between levels of angiotensinogen mRNA and its protein inthe liver (r = 0.53,P<0.01, n = 25) and inthe kidney (r = 0.75,P<0.0001, n = 24). Thesefindings demonstrate that there is a significant increase in both hepatic andrenal angiotensinogen gene expression in the last third of gestation in thefetal sheep and that this increase is associated with an increase ofangiotensinogen levels in both tissues. This increase in angiotensinogen inlate gestation could influence the activity of both the intrarenal andcirculating renin angiotensin systems.