Springer Online Journal Archives 1860-2000
Summary In rats during perinatal, suckling, weaning, sexual maturation and adult periods (ages 1, 10, 20, 40 and 80 days) we determined the concentration of renin (PRC) and its substrate (RSC) in blood plasma, and renin (RRA) and “angiotensinase” (RAA) activity in the kidney. These measurements were complemented by determinations of glomerular counts per unit weight (CG) of kidneys of animals aged 20, 40 and 80 days. From age 40 days the sexes were separated. Between ages 1 and 20 days, PRC values were higher than in adults, whereas RSC was at the same level. The highest PRC values were found in 1-day-old animals, where we also showed the highest RRA values. Between ages 1 and 10 days both parameters decreased. Between ages 40 and 80 days there was no sex difference in PRC, whereas RRA decreased in males as in the case of CG. In adults, RRA in males was lower by 25 and CG by 30% than in females. RAA was lower at ages 1–20 days than in adult animals. At the time of sexual maturation these values increased, earlier and to a more marked degree in males than in females. It is argued that a) the origin of the sex differences of RRA is related to the decrease in concentration of structures containing this activity in the male kidney. This may result in part from a more rapid rate of growth of structures containing RAA; b) that in early postnatal ontogenesis inactivation of angiotensin in the kidneys can be lower, and its formation in the body fluids higher than in adult animals.
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