Demonstration of glomerular DPP IV activity in kidney diseases

Dipeptidylpeptidase IV (DPP IV) activity has been found in glomeruli of the rat and other previously investigated animal species, but has not been detected in the glomeruli of the normal human kidney. Under pathological conditions, enzyme activity may be registered. Following investigations on 155 human renal biopsies using polyclonal antisera against IgG, IgA, IgM, C3C, Fibrinogen, and DPP IV, we found glomerular enzyme activity in 43 cases of various histological diagnoses, but never in normal renal tissue. Identical results could be found by the Gly-Prol-beta-MNA substrate reaction. The localization of glomerular enzyme activity in capillary walls could not be definitely determined, possibly enzyme activity occurs in podocytes. Correlation of glomerular DPP IV activity to the deposition of immunoglobulins was not found. Nevertheless, the appearance of DPP IV in human glomeruli seems to be in correlation with some clinical findings, e.g. hypertension. The importance of DPP IV activity in pathohistologically changed glomeruli of human kidney is definitely large, but needs further investigation.