Compensatory renal growth in the mouse. III. Growth hormone and insulin deficiency.

The effect of combined insulin and growth hormone (GH) deficiency on compensatory renal growth (CRG) was studied in the dwarf mouse, "Little," after insulin suppression with streptozotocin (SZ). Nucleic acid and protein estimations were used to assess changes in cellular hyperplasia and hypertrophy. Mice aged 30 days received SZ while controls received buffers solution alone. Left nephrectomy was performed at 35 days of age with removal of the renoprival kidney 15 days later. In mice with normal GH, renoprival kidney weight was unaffected by SZ, but the total DNA (estimate of cell number) was higher than normal in both sham-operated and renoprival kidneys suggesting that insulin suppression may cause greater cell replication during both normal growth and CRG. The ratio of protein to DNA (estimate of cell size) in the renoprival kidney was not suppressed by SZ as reported in muscle. In GH-deficient mice (lit/lit) given SZ, CRG was significantly diminished (P less than 0.001). Total DNA in the renoprival kidney was slightly greater than the sham-operated control (P less than 0.005) but the protein:DNA ratio (cell size) was unchanged. These results suggest that when both GH and insulin are suppressed, adaptive cellular growth is inhibited. The proposal that GH and insulin are the two primary hormones controlling cellular growth is consistent with these results.