Effect of Sulfur-Containing Compounds on Experimental Diabetes. XI. Effect of Thiol and Disulfide Compounds on Glucose Transfer into Red Blood Cells

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Studies were made on the influence of thiol and disulfide compounds on glucose uptake into red blood cells (RBC) of normal and alloxan diabetic rats. 1) Incorporation of glutathione (GSH), 2-mercaptopropionylglycine (MPG), oxidized GSH and oxidized MPG into RBC was examined. MPG was found to be incorporated into RBC. When MPG was allowed to react with RBC at 37° for 30 minutes, approximately 30% of MPG in the reaction solution was incorporated into RBC (alloxan diabetic (AD)-RBC). Four to ten per cent of the incorporated MPG existed in the oxidized form. 2) Incorporation of glucose into normal RBC and AD-RBC was examined. Incorporation of glucose into AD-RBC was inhibited. 3) In normal RBC, such compounds as MPG and cystein which were incorporated into RBC increased glucose uptake, while GSH showed a tendency to inhibit incorporation of glucose. Incorporation of glucose was inhibited by oxd GSH, oxd MPG and cystine. 4) Influence of various inhibitors was studied. Incorporation of glucose was inhibited by SH reagents (HgCl₂, parachloromercuribenzoate (PCMB), parachloromercuribenzene sulfonate (PCMBS), NEM), but not by insulin. Potassium borohydride increased glucose uptake. 5) Disappearance of glucose from normal RBC and AD-RBC was studied. Fifty per cent of glucose disappeared from normal RBC 9 minutes later and from AD-RBC 19 minutes later. The time required for the disappearance of 50% of glucose from normal RBC and from AD-RBC was shortened to 7 minutes and to 16 minutes respectively by the addition of MPG. As mentioned above, there is a difference in incorporation of glucose into RBC between normal RBC and AD-RBC. Furthermore, promotion of glucose uptake by MPG and cysteine and inhibition of glucose uptake by oxd MPG and cystine were discussed.