Effect of nonsupressible insulin-like protein on glomerular protein synthesis

Partially purified preparations of NSILP were evaluated for effect on incorporation of labeled precursors into protein, collagen, and basement membrane by isolated rat renal glomeruli. Dowex-adsorbed NSILP (0.5 mU/mg) inhibited the secretion of protein and collagen and resulted in a significant diminution of incorporation of labeled lysine into glomerular basement membrane. Glomerular protein and collagen secretion were also inhibited in the presence of Sephadex G-200 NSILP (4.5 mU/mg), but an effect on incorporation of radiolabeled proline, hydroxyproline, lysine, and hydroxylysine into glomerular basement membrane was not observed. The in vitro response of renal glomeruli to NSILP constitutes another "insulin-like" effect of this substance.