Dopamine-beta-hydroxylase activity in plasma, spleen and adrenal gland of streptozotocin-diabetic rats: correlation with cataracts

Abstract

In streptozotocin-diabetic rats a large increase in plasma dopamine-beta-hydroxylase activity was observed.This increase returned to control values with sufficient insulin doses (6 I.U/day); lower insulin doses did not allow normal level to be reached, a dose-dependent decrease being observed.Although the glycemia levels in the diabetic state are responsible for the plasma dopamine-beta-hydroxylase, there is no exact ratio between these two parameters when diabetic animals are treated with different insulin doses which suggests not only the clearance of plasmatic dopamine-beta-hydroxylase, but a contribution from exocytotic tissues as well.In the experimental conditions, before cataracts appeared, the animals about to develop opaque lenses showed a greater dopamine-beta-hydroxylase activity than those which were to remain without this complication.After three months in diabetic state, the severity of disease was evident in the animals with cataracts since they showed a significantly higher function of the sympathoadrenal axis, expressed in spleen and adrenal dopamine-beta-hydroxylase activity.Plasma dopamine-beta-hydroxylase, as a minority glycoprotein can be considered a useful parameter of other mannose-terminal glycoproteins without having a well-known function, and also as a high risk protein, the accumulation of which in several places contributes to the complex pathogenic mechanism of diabetes complications.