Impaired contractile responsiveness of diabetic glomeruli to angiotensin II: a possible indication of mesangial dysfunction in diabetes mellitus.

The contractile function of renal glomerulus was studied in vitro using isolated glomeruli from streptozotocin-diabetic rats. Glomerular contraction was assessed by the reduction of extracellular [3H]inulin space of glomerulus, mostly composing of intracapillary space, produced by angiotensin II. The inulin space was dose-dependently reduced after angiotensin II addition in both diabetic and control rats but the degree of reduction significantly smaller in the former. The radioreceptor assay revealed rather increased angiotensin II receptors in diabetic glomeruli. Since the contractile response of glomerulus to angiotensin II is mediated via mesangial cell contraction, these results suggest the presence of mesangial cell dysfunction in diabetes.