Relations among transepithelial sodium transport, potassium exchange, and cell volume in rabbit ileum.

Abstract

The relation between active transepithelial Na transport across rabbit ileum and 42K exchange from the serosal solution across the basolateral membranes has been explored. Although 42K influx across the basolateral membranes is inhibited by ouabain and by complete depletion of cell Na, it is not affected when transepithelial Na transport is abolished (i.e. in the presence of an Na-free mucosal solution) or stimulated (i.e. when glucose or alanine is added to the mucosal solution). We are unable to detect any relation between the ouabain-sensitive Na-K exchange mechanism responsible for the maintenance of intracellular Na and K concentrations and active transcellular Na transport. In addition, the maintenance of cell volume (water content) does not appear to be dependent upon transepithelial Na transport or the ouabain-sensitive Na-K exchange pump. Although the results of these studies cannot be considered conclusive, they raise serious questions regarding the role of the Na-K exchange pump, located at the basolateral membranes, in active transepithelial Na transport and the maintenance of cell volume.

Epithelial transport pathways of rat colon determined in vivo by impulse response analysis.

“…The apparent dissociation between the actions of cyanide on transepithelial Na transport (almost completely inhibited) and on the cellular K (little or no effect) must raise some doubts as to whether the ionic pumps maintaining cellular composition are also those concerned in Na transport. Similar doubts have been raised by in vitro studies with ouabain on rabbit ileum (Nellans & Schultz, 1976). Model for ionic fluxes from the blood.…”

Possible Sodium and D-Glucose Cotransport in Isolated Jejunal Epithelium of Children

“…For this measurement, 3H inulin has been used for a long time on human (12,14) and on animal intestine (32,35). Its validity has been recently reassessed in rabbit ileum (24). The high molecular weight of inulin, 5000 daltons, could, however, lead to an underestimation of the extracellular space.…”

“…The intracellular concentration of D-glucose and of Na was always determined on the same piece of tissue by means of measurement of isotopic tracer: 2.5 pCi I4C (U) D-glucose, 0.5 pCi 22 Na (Cornmisariat a 1'Energie Atomique, Gif, France), and 12.5 pCi 3~ Inulin Methoxy (New England Nuclear) as extracellular marker (21,24).…”

Mouse mammary epithelial cells on floating collagen gels: Transepithelial ion transport and effects of prolactin

“…However, the cytological location of this enzyme has come into doubt recently (34). In addition, there is still a question about the exact correlation between Na+,K+-ATPase activity and transepithelial Na+ transport (35,36). This culture system may provide a means for determining the effects of prolactin on Na+,K+-ATPase activity of the mammary epithelial cells and what relationship this has to transepithelial Na+ transport, without the complications inherent in whole glands or tissue slices of heterogeneous cell populations.…”