Inhibitory effect of vanadate on protein phosphatase, glycogen phosphorylase and protein kinase in extracts from...

The purpose of this study was to determine the in vitro effect of increasing vanadate concentrations (1 nm-I mm) on protein phosphatase (PP) and glycogen phosphorylase (GP) of extracts from several rat tissues. PP activity was inhibited in various brain structures by moderate concentrations of vanadate; however, in the spinal cord, comparatively low concentrations (10 nm) of vanadate caused a steep increase in enzyme activity. Only at a high concentration (1 mm) did vanadate produce moderate PP inhibition. Reciprocal correlation was obtained between vanadate effects on PP and GP in various parts of the nervous system. In the last series of experiments the effect of vanadate upon protein kinase (PK) activity in various regions of the CNS was determined; low and intermediate vanadate concentrations produced a moderate activation; higher vanadate concentrations suppressed the enzyme activity. Vanadate at a concentration of 0.1 mm produced activation of PK in the medulla oblongata, whereas at 1 mm vanadate there was significant inhibition of PK. The spinal cord enzyme was more sensitive to vanadate, being inhibited at concentrations of 10 nm-1 mm.