Effect of adrenocorticoid receptors on potassium and sodium flux in rat C6 glioma cells.
C6 glioma cells contain two types of receptors for adrenocorticoids. Glucocorticoid (Type II) receptors are present at higher density and mediate increases in glycerol phosphate dehydrogenase and glutamine synthetase activity. The function of mineralocorticoid (Type I) receptors present at low density in C6 cells is unknown. Since mineralocorticoid (Type I) receptors in renal epithelial cells regulate cation transport, we sought to determine whether adrenocorticoid receptors located in glioma cells are similarly linked to electrolyte transporting activity. Occupation of mineralocorticoid receptors in C6 glioma by adrenocorticoids did not alter Na+ or K+ transport, in contrast to their effects on renal epithelial and vascular smooth muscle cells. Occupation of glucocorticoid receptors produced a 20-25% decrease in K+ uptake into C6 cells, but did not alter Na+ influx. Stimulation of Na+ influx with the ionophore monensin produced a large ouabain-sensitive increase in glucose utilization, as measured by 2-deoxyglucose uptake. However, mineralocorticoid receptor occupation did not alter glucose utilization, providing further evidence that these receptors do not influence Na+ transport in C6 cells. These studies provide evidence that mineralocorticoid receptors in glioma cells do not regulate Na+ or K+ transport. Glial glucocorticoid receptors have an inhibitory effect on glial K+ influx, which may contribute to glucocorticoid hormone effects on brain excitability.
Beaumont
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Department of Medicine, University of California, San Diego, La Jolla 92093.
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D000818:Animals; D003847:Deoxyglucose / Q000378:metabolism; D005910:Glioma / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000502:physiology*; D018161:Receptors, Mineralocorticoid; D011987:Receptors, Steroid / Q000502:physiology*; D012964:Sodium / Q000378:metabolism*; D014407:Tumor Cells, Cultured / Q000378:metabolism
D011965:Receptors, Glucocorticoid; D018161:Receptors, Mineralocorticoid; D011987:Receptors, Steroid; D003847:Deoxyglucose; D012964:Sodium; D011188:Potassium