Parotid gland basement membrane variation in diabetes mellitus

Post-mortem samples of parotid gland were obtained from 15 patients with a history of diabetes mellitus for a minimum of 5 years, and from 15 age- and sex-matched controls. The tissue was studied by direct immunofluorescence for abnormal binding of selected serum proteins, including IgG, IgM, IgA, C3, fibrinogen, polyvalent immunoglobulin and albumin, to acinar and ductal basement membranes of the gland. Thickness of these basement membranes was also assessed using a calibrated magnifier on uniformly enlarged photomicrographs of the tissue which had been stained by the chromotrope silver methenamine method to highlight basement membranes. Results of this investigation revealed parotid gland basement membrane abnormalities in all diabetic subjects as indicated by the binding of IgG, albumin and polyvalent immunoglobulins to ductal and acinar basement membranes. These basement membranes were uniformly negative in control subjects for the binding of all serum proteins tested. Binding of IgA was also noted in 7 of 15 experimental subjects, with 6 of these representing Type I diabetics. Basement membrane measurements revealed no difference in thickness between diabetic and non-diabetic subjects. Variations in parotid diabetic basement membranes evidenced in this study further substantiate the idea that membranopathy in this disease is systemic in nature.