Mast cell degranulation and blood-nerve barrier permeability in rat sciatic nerve after 7 days of hyperglycemia.

The association between hyperglycemia and altered blood-nerve barrier permeability was examined after 7 days of experimental diabetes. In nerves of rats fed a diet of 40% galactose, permeability to [14C]mannitol [13.43 +/- 2.47 x 10(-5) (SD) ml.s-1.g dry wt-1] and water content [3.43 +/- 0.24 (SD) mg/mg dry wt] were significantly increased compared with control (9.24 +/- 2.09 x 10(-5) ml.s-1.g dry wt-1 and 2.15 +/- 0.28 mg/mg dry wt) and streptozotocin-diabetic animals (8.43 +/- 2.94 x 10(-5) ml.s.-1.g dry wt-1 and 2.35 +/- 0.56 mg/mg dry wt). Electron microscopy revealed significant increases in the number of degranulating perivascular mast cells and in an index of vasoconstriction in galactose-treated rats (3.8 +/- 1.6 and 0.160 +/- 0.062, respectively) compared with control (0.5 +/- 0.8 and 0.072 +/- 0.017, respectively) and diabetic animals (1.4 +/- 1.7 and 0.083 +/- 0.033, respectively). The data are consistent with a role for mast cells in permeability changes occurring after only 7 days of galactose intoxication.