Ontogenesis of the renin-angiotensin system in spontaneously hypertensive and normal Wistar rats.

Abstract

Kidney renin activity was investigated in spontaneously hypertensive and normotensive control Wistar rats. Kidneys were obtained from fetal rats after 18 and 21 days of gestation and from neonatal rats 1, 7, 14, and 21 days old. Kidney renin activity was determined by a modification of the radioimmunoassay for angiotensin I developed in this laboratory, and tissue from each age group was stained for juxtaglomerular granules. Kidney renin activity progressively increased in both strains from day 18 of fetal life until day 1 of neonatal life when a plateau level developed. In 1-day-old neonatal rats, significant differences in the kidney renin activity of the spontaneously hypertensive and the normotensive strains were initially noted. Kidney renin activity was maintained at significantly higher levels in the spontaneously hypertensive strain under 21 days of age when, because of a rise in the kidney renin activity of the normotensive control strain and a fall in the kidney renin activity of the spontaneously hypertensive strain, the difference between the two strains became statistically insignificant. In both strains, juxtaglomerular granules were first noted in 1-day-old neonatal rats and in each age group thereafter.