Uptake and efflux of 3-O-methyl-D-glucose in rat parotid cells

In the framework of recent investigations on the regulation of D-glucose production by salivary glands, the aim of the present study was to compare the uptake of 3-O-[14C] methyl-D-glucose by rat parotid cells over a 6-min incubation period at 37 degrees C to its efflux from prelabelled parotid cells, also incubated for 6 min at 37 degrees C. It was first assessed that the intracellular (HOH)-H-3 water space, whether expressed in absolute terms or relative to the total 3HOH distribution space, is not significantly different between parotid cells obtained from either control rats or streptozotocin-induced diabetic rats. In the control rats, the uptake of 3-O-[14C] methyl-D-glucose corresponded, following correction for extracellular contamination, to a mean distribution space of 0.44 +/- 0.05 nl/103 cells, representing 29.8 +/- 3.4% of the intracellular water space. The efflux of 3-O-[14C] methyl-Dglucose from prelabelled parotid cells, expressed relative to their initial radioactive content, averaged 82.9 +/- 4.8 and 84.1 +/- 2.5% in control and diabetic rats, respectively. These findings suggest that the increased production of salivary D-glucose in diabetic subjects may be attributable to hyperglycemia, rather than to any major perturbation of the intrinsic processes involved, at least in parotid cells, in hexose handling.