Effect of tityustoxin and ouabain on protein phosphorylation in a crude synaptosome fraction.

1. The effect of tityustoxin (TsTX) and ouabain on the incorporation of 32P into a protein of the same apparent molecular weight as synapsin I is described. 2. Tityustoxin-stimulated protein phosphorylation in a crude synaptosome fraction increased up to a concentration of 3.0 microM at an incubation time of 15 s. 3. Trifluoperazine (100 microM) inhibited, while trifluoperazine sulphoxide (100 microM) did not alter the effect on the protein phosphorylation induced by tityustoxin. 4. Unlike tityustoxin, ouabain (100 microM) had no effect on protein phosphorylation even after incubation up to 20 min. 5. Ouabain at 10 microM, a concentration having no effect on rates of respiration and ATP hydrolysis in brain cortical slices, also had no effect on protein phosphorylation.