Initial renal growth in diabetic and sodium-loaded spontaneously hypertensive rats (SHR)

An increase in kidney size in experimental diabetic rats is ascribed to local somatomedin C (SM-C) formation. In the present study, we compared the nature of the initial kidney growth following sodium-load in spontaneously hypertensive rats (SHR) with that in streptozotocin-induced diabetic SHR. After 6 d of each treatment, the kidney weight increased in both groups. SM-C levels in the kidney increased in diabetic SHR on day 2, unaccompanied by any considerable change in plasma SM-C. In sodium-loaded SHR, kidney SM-C content was not changed and plasma SM-C rather declined on day 6. Protein content including both non-collagen protein and collagen protein increased in both diabetic and sodium-loaded groups, whereas DNA content increased only in the latter group. Protein/DNA ratio increased in diabetic rats but not in sodium-loaded animals. It may be estimated, therefore, that diabetic kidney growth in SHR is mainly due to cellular hypertrophy which is related to SM-C formation, while kidney growth following sodium-load is due to hyperplasia which may be independent of local SM-C formation.