Retention of insulin‐stimulated D‐glucose transport activity by adipocyte plasma membranes following extraction of extrinsic proteins

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Abstract
Plasma membrane vesicles prepared from adipocytes incubated with insulin exhibited accelerated D‐glucose transport activity characteristic of insulin action on intact fat cells. Both control and insulin‐stimulated D‐glucose transport activities were inhibited by cytochalasin B and thiol reagents. Extraction of plasma membranes with dimethylmaleic anhydride eluted 80% of the protein from plasma membrane vesicles. The two major glycoprotein bands (94,000 and 78,000 daltons) and small amounts of a 56,000‐dalton band were retained in dodecyl sulfate gels of the extracted membranes. Both control and insulin‐activated D‐glucose transport activities were retained by plasma membrane vesicles extracted with dimethylmaleic anhydride. Cytochalasin B binding activity was also retained by extracted membrane vescles and D‐glucose uptake into extracted vescles derived from untreated or insulin‐treated fat cells was inhibited by cytochalasin B. These results suggest that the modification of the adipocyte hexose transport system elicited by insulin action is not altered by a major purification step which involves quantitative extraction of extrinsic membrane proteins.