Molecular biology of components of the renin-angiotensin system during development

Evidence for the expression of genes of the renin-angiotensin system (RAS) in the developing kidney is rapidly accumulating. We have recently demonstrated that the fetal kidney expresses the renin gene and that expression of the gene is developmentally regulated. Kidney renin messenger ribonucleic acid (mRNA) levels decrease markedly with maturation, and as maturation unfolds the intrarenal distribution of renin and its mRNA changes from large intrarenal arteries in the fetus to a restricted juxtaglomerular site in the adult animal. These findings demonstrate that renin is synthesized and stored in the aforementioned vascular segments and that expression of the renin gene follows the centrifugal pattern of nephrovascular development. In addition to storing renin, intact kidney microvessels release renin spontaneously and possess a functionally active adenylate cyclase whose stimulation results in a marked increase in renin release. The increase in renin enzymatic activity appears to be due to a recruitment of renin-releasing cells rather than to an increase in the amount of renin secreted per cell. Expression of the angiotensinogen (Ao) gene is also developmentally regulated. Ao mRNA levels are very low in the fetal liver, markedly increasing after parturition, suggesting that some of the complex neurohumoral changes surrounding extrauterine life may regulate the expression of the Ao gene. As in the adult animal, Ao is expressed in fetal kidney, brain and brown adipose tissue. The contribution of these organs to the fetal plasma pool of Ao remains to be determined. However, unlike the adult, the fetal liver may not be the primary source of circulating Ao in the fetus.(ABSTRACT TRUNCATED AT 250 WORDS)