Vacor-administrated rats showed the thickening of the glomerular basement membrane (GBM). To investigate how the glomerulopathy occurs, the amounts of total and guanidine HCl soluble-type IV collagen and laminin in the glomeruli of the Vacor-administrated diabetic rats were assayed. A single dose of Vacor (40 mg/kg) was administrated to adult male Wistar rat (200 - 250 g) using orogastric cannula. The rats were sacrificed at 0, 1, 2, and 4 weeks after Vacor administration and the glomeruli were purified with sieve method. The amounts of type IV collagen and laminin were assayed by dot blot with each corresponding antibodies. The total amounts of type IV collagen and laminin of the control rats were 1.5 mg/104 glomeruli and 200 microgram/104 glomeruli, respectively. The type IV collagen of the Vacor-induced diabetic rat glomeruli was increased to 140% and 190% at 2 and 4 weeks after Vacor administration compared to that of control rat glomeruli respectively. The laminin was also increased to 120%, 150% at 2, 4 weeks after Vacor-administration compared to that of control rat glomeruli respectively. The amounts of guanidine HCl soluble type IV collagen and laminin from the control rats were 350 microgram/104 glomeruli and 200 microgram/104 glomeruli. The soluble collagen was decreased to 56% and 40% at 2 and 4 weeks after Vacor administration. But the amounts of soluble laminin not changed. These data suggest that the increases of total amounts of type IV collagen and laminin and the increases of cross-link of type IV collagen might cause the thickening of GBM and diabetic glomerulopathy.