Intrarenal distribution of renin in the developing rabbit

The purpose of this study was to evaluate the intrarenal distribution of renin in individual glomeruli during development in the rabbit. Superficial cortical and juxtamedullary glomeruli were obtained from animals at 1, 2, and 4 wk of age and from adults to determine renin concentration. In addition, kidney weight, total renal renin content, plasma renin concentration, and plasma angiotensin I concentration were also measured during this time period. Superficial cortical glomerular renin concentration at 1 wk of age averaged 7.7 +/- 1.6 (S.E.M.) pg/h whereas juxtamedullary glomerular renin concentration was 4.5 +/- 1.8 pg/h. There was no difference in concentration between the superficial and deep glomeruli at this age. At 2 wk of age, however, superficial glomerular content had increased significantly to 143.8 +/- 2.94 pg/h whereas the juxtamedullary concentration remained unchanged (7.9 +/- 1.6 pg/h). The concentration in the superficial nephrons continued to increase with age. At 4 wk, superficial renin content was 224.6 +/- 27.2 whereas the deep nephrons did not change (16.0 +/- 7.5 pg/h). Adult animals demonstrated a further increase to 842.7 +/- 15.1 pg/h in the superficial nephrons whereas the deep nephrons continued to remain low (15.9 +/- 4.7 pg/h). The results of this study demonstrate that after the first week of life there was significantly more renin activity in glomeruli in the outer cortex than in the juxtamedullary cortex. Total renal renin concentration increased with age and showed a significant positive correlation with the concomitant increase in kidney weight. But renal renin content increased more than kidney weight between 1-2 wk of age.