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

Incubation of rat brain homogenates with thiamine or thiamine diphosph ate (TDP) leads to a synthesis of thiamine triphosphate (TTP). In memb rane vesicles subsequently prepared from the homogenates, increased TT P content correlates with increased Cl-36(-) uptake. A hyperbolic rela tionship was obtained with a K-0.5 of 0.27 nmol TTP/mg protein. In cru de mitochondrial fractions from the brains of animals previously treat ed with thiamine or sulbutiamine, a positive correlation between Cl-36 (-) uptake and TTP content was found. These results, together with oth er results previously obtained with the patch-clamp technique, suggest that TTP is an activator of chloride channels having a large unit con ductance.