Membrane structural/functional properties of adipocytes from normal and streptozotocin-diabetic rats

The uptake of 2-deoxy-D-[1-14C]-glucose, in the presence and absence of insulin, was measured in adipocytes from normal and streptozotocin-diabetic animals, over a wide temperature range (25-45 degrees C). Optimum temperatures for uptake in the presence of maximally stimulating insulin concentrations occurred near physiologic temperatures. Both high and low temperatures lead to progressive inhibition of insulin-sensitive uptake, whereas basal uptake was only marginally affected. It is possible that the apparent "resistance" to insulin action at high (febrile) temperatures may have pathologic significance. The magnitude of 2-deoxy-D-glucose uptake at all temperatures in the diabetic adipocytes was much reduced, both in the presence and absence of insulin, on a per cell basis, compared with cells from age-matched control animals. However, the fold stimulation of uptake caused by insulin at 35 degrees C is comparable in both normal and diabetic adipocytes (approximately 2-3-fold). Photomicrographs of adipocytes were used to estimate the cell diameters of the average normal (50 micron) and diabetic (37 micron) cells. The diabetic adipocytes are not "resistant" to insulin action in terms of 2-deoxy-D-glucose uptake since the basal and insulin-stimulated uptake magnitudes per micron2 membrane surface area are identical in both normal and diabetic cells (within experimental error). It is possible that the decreased diabetic cell size reflects the reduced antilipolytic effects of chronic hypoinsulinemia rather than any inherent resistance to insulin action in the cell itself.(ABSTRACT TRUNCATED AT 250 WORDS)