CHLORIDE PERMEABILITY OF RAT-BRAIN MEMBRANE-VESICLES CORRELATES WITH THIAMINE TRIPHOSPHATE CONTENT

Incubation of rat brain homogenates with thiamine or thiamine diphosphate (TDP) leads to a synthesis of thiamine triphosphate (TTP). In membrane vesicles subsequently prepared from the homogenates, increased TTP content correlates with increased Cl-36(-) uptake. A hyperbolic relationship was obtained with a K-0.5 of 0.27 nmol TTP/mg protein. In crude mitochondrial fractions from the brains of animals previously treated with thiamine or sulbutiamine, a positive correlation between Cl-36(-) uptake and TTP content was found. These results, together with other results previously obtained with the patch-clamp technique, suggest that TTP is an activator of chloride channels having a large unit conductance.