The influence of insulin and insulin antibodies on the glomerular structure

Guinea pigs and rabbits were treated with heterologous insulin preparations of different purity for 3 months without Freund's adjuvant. The insulin binding capacity of the serum, as well as the light and electron microscopic structure of the glomeruli were studied and the glomerular structure was analyzed with quantitative methods. By a longer treatment with heterologous commercial insulin preparations a proliferation of mesangial cells and a thickening of the mesangium matrix were showed. Furthermore, hump-like basement membrane protuberances were found in the glomerular capillary wall. Their frequency increased when more insulin antibodies were formed. Rabbits treated with MC insulin showed no significant antibody formation and no significant changes in the glomerular structure. Otherwise, in animals treated with the impurities of the insulin preparations (a+b component) a marked increase in the basement membrane protuberances was demonstrable accompanied by a higher antibody titer. An increase in the mesangial cell density as well as an increase in the mesangial volume were also present. The results confirm the findings that a contaminating protein in crystalline insulin to be responsible for the antigenic properties.