Effect of thiols in biological systems on protein sulfhydryl content

Abstract

An erythrocyte plasma system was incubated with various thiols (final concentration, 0.003 M) to study the effects on protein sulfhydryl content. After timed incubation, the plasma sulfhydryl concentration, i.e. the protein and nonprotein fractions, was determined by polarographic analysis. The results indicate that sulfhydryl groups of the thiol were transferred or converted to increase the protein sulfhydryl content in the presence of tissue sulfhydryl groups. An increase of protein sulfhydryl did not take place in the absence of cellular elements and was partially inhibited by first blocking the sulfhydryl groups of the cellular elements. Studies in vivo were also conducted to determine whether the sulfhydryl groups of the thiols can be exchanged with, or converted to, tissue protein sulfhydryl groups. N-acetylcysteine was given intravenously in Swiss mice and the protein and nonprotein sulfhydryl content of various tissue fractions was assayed. Distribution studies after administration of the 35S-labeled N-acetylcysteine were conducted utilizing autoradiographic procedures. A significant increase in the tissue protein sulfhydryl content was again achieved in vivo. These findings support the hypothesis that thiols can be utilized to increase tissue sulfhydryl groups when the latter are deficient, as reported in various clinical disorders. The approach may, therefore, have therapeutic application.