³²P, ⁸⁶Rb⁺ and ⁴⁵Ca²⁺ Handling by Tumoral Insulin-Secreting Cells (RINm5F Line)

Summary

In perifused tumoral islet cells (RINm5F line), which were prelabelled with either [³²P]orthophosphate, ⁸⁶Rb⁺ or ⁴⁵Ca²⁺, the administration of D-glucose (1.4, 2.8 or 16.7 mM) increased the efflux of ³²P, decreased the outflow of ⁸⁶Rb, increased slightly the efflux of ⁴⁵Ca from cells perifused in the presence of Ca²⁺, and decreased modestly the outflow of ⁴⁵Ca from cells perifused in the absence of Ca²⁺. D-glucose also stimulated the net uptake of ⁴⁵Ca²⁺. When Ba²⁺ (2 mM) was used, in the absence of Ca²⁺, instead of D-glucose as an insulin secretagogue, the efflux of ³²P was little affected, but the outflow of ⁴⁵Ca was dramatically increased. These changes are qualitatively similar to those occurring in normal islet cells. Nevertheless, the ionic response to D-glucose appeared, as a rule, less marked in tumoral than normal islet cells. Moreover, the concentration-response relationship was shifted to a lower range of hexose concentrations in the RINm5F cells.

Key-Words

RINm5F Cells - Tumoral Insulin-Secreting Cells - Perifusion - ³²P Handling - ⁸⁶Rb⁺ Handling - ⁴⁵Ca²⁺ Handling - Glucose - Calcium Deprivation - Ba²⁺