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°C to its efflux from prelabelled parotid cells, also incubated for 6 min at 37°C. It was first assessed that the intracellular 3HOH 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-D-glucose 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.