The effect of hyperosmotic challenge upon ion transport in cultured renal epithelial layers (MDCK)

✍ Scribed by N. L. Simmons; D. R. Tivey

• Publisher: Springer
• Year: 1992
• Tongue: English
• Weight: 852 KB
• Volume: 421
• Category: Article
• ISSN: 0031-6768
• DOI: 10.1007/bf00370263

✦ Synopsis

Exposure of the basal-lateral surfaces of MDCK epithelia, mounted in Ussing chambers, to medium made hyperosmotic by the non-electrolyte mannitol, resulted in a marked inhibition of the adrenalinestimulated inward short-circuit current (C1-secretion). This inhibition was unaccompanied by a reversal of the adrenaline-stimulated increment in tissue conductance, indicating that the inhibition was due to modulation of ion transport at the basal-lateral membranes. Loop-diuretic-sensitive 86Rb(K +) efflux mediated by the Na + -K + -2 CI-cotransporter at the basal-lateral membranes was markedly stimulated by hypertonic exposure. A diuretic-sensitive K+(C1 -) loss was observed in shrunken cells upon prolonged exposure (20 rain), showing that the net direction of "cotransport" flux was outward. 86Rb(K+) efflux stimulated by adrenaline (100gM), exogenous ATP (100 gM) and A23187 (10 gM) was attenuated in shrunken cells, suggesting that basal-lateral K + conductance is reduced in hyperosmotic media. "Cotransport" stimulation by hyperosmotic medium was asymmetric, apical bathing hypertonicity being ineffective. These data are consistent with a low hydraulic permeability of the apical membranes.