IMMUNOHISTOCHEMICAL QUANTIFICATION OF HEPARAN-SULFATE PROTEOGLYCAN AND COLLAGEN-IV IN SKELETAL-MUSCLE CAPILLARY BASEMENT-MEMBRANES OF PATIENTS WITH DIABETIC NEPHROPATHY

In IDDM patients, an increased permeability of the glomerular capillar ies has been associated with a general loss of negatively charged hepa ran sulfate proteoglycans (HSPGs) within basement membranes (BMs). In the present study, we used immunohistochemical staining to quantify he paran sulfate (HS), HSPG core protein, and collagen IV in capillary ba sement membranes of skeletal muscle biopsies taken from 9 healthy cont rol subjects (C) and 20 IDDM patients: 7 with normal albumin excretion rate (<30 mg/24 h) (D-0), 5 with incipient nephropathy (albumin excre tion rate 30-300 mg/24 h) (D-1), and 8 with clinical nephropathy (albu min excretion rate >300 mg/24 h) (D-2). In the capillaries, staining w as measured by a scanning and integrating microspectrophotometer. A si gnificant difference in the absorbance of HS was found among the four subgroups (means +/- SD): 0.477 +/- 0.082 (C), 0.627 +/- 0.031 (D-0), 0.542 +/- 0.098 (D-1), and 0.371 +/- 0.118 (D-2) (P = 0.006). Similarl y, an overall significant difference in the absorbance of collagen IV was demonstrated (means +/- SD): 0.836 +/- 0.111(C), 0.838 +/- 0.300 ( D-0), 0.970 +/- 0.173 (D-1), and 0.512 +/- 0.248 (D-2) (P = 0.02). No statistical difference in the absorbance of core protein was demonstra ted among the groups. Within the diabetic groups, HS was inversely cor related to albuminuria (r = -0.76, P = 0.003) and albuminuria correcte d for creatinine clearance (r = -0.69, P = 0.008). Because, in IDDM pa tients with albuminuria, alterations of the content of HS and collagen TV within the capillary BM have been demonstrated immunohistochemical ly, not only in the glomerular filtration barrier, but also in the ske letal muscle capillary BM, we suggest that these changes reflect unive rsal quantitative or qualitative alterations within the capillary filt ration barrier.