Inhibitory effect of hypophysectomy and food restriction on glomerular basement membrane thickening, proteinuria and renal enlargement in aging male Wistar rats

Age-related thickening of the glomerular basement membrane (GBM) was studied in three groups of male Wistar rats: (a) ad libitum fed, (b) hypophysectomized and (c) food-restricted eating the same amount of food as hypophysectomized rats, but about 45% of the ad libitum fed group. Studies were begun at 50 days (2 months) and continued throughout life. Multiple regression was used to statistically assess the effects of age and treatments. In ad libitum fed male rats GBM thickness increased from 114 nm at 50 days (2 months) to 632 nm at 1,000 days (33 months). GBM thickness at 1,000 days was 296 nm in hypophysectomized rats and 392 nm in food restricted rats. Hypophysectomy had a significantly greater inhibitory action on GBM thickening than food restriction, in rats eating the same quantity of food per day. However, a major part of the effect of hypophysectomy may be due to the permanent fall in food intake (from 16.3 to 7.9 g/day) resulting from the operation. Accompanying the age-related thickening of the GBM in ad libitum fed rats were proteinuria and renal enlargement, both of which were inhibited by hypophysectomy and food restriction.