Molecular and cellular aspects of renin during kidney ontogeny.

The activity of the renin-angiotensin system is subjected to remarkable developmental changes. Circulating as well as renal concentrations of renin are high in early life, decreasing progressively as maturation evolves. This review summarizes the current molecular framework underlying those changes during kidney development. Evidence is presented demonstrating that expression of the renin gene is developmentally regulated. Renin messenger ribonucleic acid (mRNA) levels are higher in fetuses and newborns than in adult mammals. As maturation progresses, the distribution of renin and its mRNA shifts from large intrarenal arteries in the fetus to the classic juxtaglomerular localization in the adult. Potential explanations for these changes as well as the cytosolic events mediating renin release and gene expression are discussed. Evidence is also presented demonstrating that under diverse physiologic and pathologic conditions the adult kidney vasculature has the capability to recruit renin gene expressing and/or containing cells. Throughout, an effort has been made to identify gaps in our knowledge. Not without bias, we hope that future research in this area will lead to a better understanding of the biology of renin in the developing as well as the adult individual.