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J Eggenton

Publications and source records attributed to J Eggenton.

9 recordsLinked to original sources
PubMed1972

Membrane potentials of epithelial cells in rat small intestine.

1. Stripped sacs of rat jejunum in which the outer muscle layers had been removed were found to maintain substantial transport and electrical activities.2. Mucosal and serosal membrane potentials of epithelial cells of normal and stripped everted sacs of rat jejunum were recorded in vitro together with the transmural potential difference.3. The cell interior was negative relative to both serosal and mucosal fluids, the transmural potential being the sum of the two membrane potentials.4. Changes in the transmural potentials in the presence of actively transferred hexoses and amino acids were entirely due to variations in the serosal potential, the mucosal potential being unchanged.5. Serosal and transmural potential increases on the addition of galactose were consistent with Michaelis-Menten kinetics, giving apparent K(m) values of 14.9 and 14.1 mM respectively.6. Phlorrhizin, ouabain, 2,4-dinitrophenol and sodium fluoroacetate inhibited serosal potential changes in the presence of galactose.7. Osmotic potentials resulting from transmural osmotic gradients originated from the serosal layers of the tissue.8. The results are consistent with the concept of a serosally located, electrogenic sodium pump which is stimulated by actively transferred hexoses and amino acids. The sodium-dependent entry mechanism at the mucosal membrane is non-electrogenic.

Alanine↗
PubMed1972

Ionic basis of membrane potentials of epithelial cells in rat small intestine.

1. Potentials across the mucosal and serosal membranes of the epithelial cells of rat jejunum together with transmural potentials were recorded using everted sac preparations.2. Ionic changes in either mucosal or serosal fluids affect mucosal or serosal membrane potentials respectively with comparable changes in the transmural potential. The contralateral membrane potential is relatively unaffected.3. Replacement of mucosal sodium chloride by potassium chloride or lithium chloride had little effect on potentials, but its replacement by mannitol or Tris chloride increased the negativity of the mucosal potential, giving linear relationships against log(10)[Na](m) with slopes of 41.4 and 30.7 mV respectively for tenfold change in [Na](m).4. At constant [Na](m), potassium or lithium increased the mucosal potential by 25.7 and 19.8 mV respectively for tenfold concentration changes.5. Qualitatively similar changes occurred in the serosal potential when the ionic composition of the serosal fluid was varied.6. Mucosal potential changes in response to modifications of the ionic composition of the mucosal fluid were the same in the presence and absence of galactose.7. Sodium and potassium diffusion potentials largely determine both the mucosal and serosal membrane potentials. For the mucosal membrane, P(K):P(Na) is 1.26:1, and is probably higher for the serosal membrane. Chloride makes no significant contribution to membrane potentials.8. Potentials generated by the electrogenic sodium pump are superimposed on diffusion potentials across the serosal membrane.

Animals↗
PubMed1969

Sodium pumps in the rat small intestine in relation to hexose transfer and metabolism.

1. The nature of Na transfer across rat jejunum was studied by measuring the Na and fluid transfers and the electrical potential in the presence of galactose, mannose and glucose.2. Galactose, actively transferred but not metabolized, caused an increase in the potential but no change in Na transfer or tissue resistance.3. Mannose, not actively transferred but metabolized, caused a large increase in Na and fluid transfer without affecting the potential or tissue resistance. Similar results were obtained with glucose in the presence of phlorrhizin.4. Galactose in the presence of mannose increased fluid and Na transfer to the level found with glucose, which is both actively transferred and metabolized.5. These results are consistent with the view that there are two Na pumps associated with hexoses in rat jejunum, both moving Na towards the serosal side. One is an electrogenic pump, stimulated by hexose transfer, and which results in a rise in potential, and the other is a neutral pump which is stimulated by hexose metabolism and which does not affect the potential.

Animals↗
PubMed1967

Relation between sodium concentration, electrical potential and transfer capacity of rat small intestine.

1. A study has been made of the effect of Na replacement in the incubation media on the hexose-dependent potential and the capacity of sacs of rat intestine to transfer fluid and galactose.2. Replacement of NaCl with mannitol or Tris Cl had little effect on the hexose-dependent potential, while replacement with LiCl and KCl had an inhibitory effect on the potential.3. Replacement with KCl, LiCl, mannitol and Tris Cl all reduced the capacity to transfer fluid and galactose, but the effects of Li and K replacement were greater than mannitol or Tris replacement.4. There is not a fixed relation between the magnitude of the potential and the amount of galactose transferred.

Animals↗