Developmental changes in intra‐enterocyte cation activities in hamster terminal ileum.

Abstract

SUMMARY1. Intracellular Na+ and K+ activities have been determined under visual control in enterocytes located at known positions along hamster ileal villi in vitro.2. The intracellular K+ activity found in enterocytes migrating over the basal third of villi was significantly less than that found in older enterocytes (83 and 113 mM respectively). The intracellular Na+ activity remained unaffected by the state of enterocyte development (32 mm throughout).3. Extracellular K+ and Na+ activities measured close to the luminal surface of the intestine were always similar to those measured in the bulk of the bathing medium. There was, however, a small difference in K+ activity detected between the bulk solution and solution near the luminal surface of enterocytes (3-4 and 3-63-7 mm respectively). Na+ activity in the villus core was also similar to that of the bathing medium.4. The brush border membrane content of sucrase-isomaltase, determined cytochemically, was found to increase rapidly as enterocytes migrated over the basal third of the villus and to plateau at a point roughly equivalent to that where intracellular K+ activities became maximal.5. The numerous ways by which enterocytes might control their intracellular K+ concentrations during development are emphasized. Attention is nevertheless drawn to the close correspondence seen between different aspects of brush border membrane development and the ability of enterocytes to maintain high internal concentrations of K+.

Effect of frusemide on Cl- channel in rat peritoneal mast cells

“…Figure 1b shows the current/voltage (I/V) relationship; the intercept with V axis was -62.9±4.1 mV (n=10). This value agrees with the behaviour of a Cl -channel and with the a,iCl value determined in the absence of cAMP (a,iCl=9.7±l.7 mM (n=4); the activity coefficient should be 0.73 [22]). …”

“…The method of construction, calibration and estimation of intracellular Cl -activities (a,iCl) was similar to that described previously for other selective microelectrodes [20,21]. Potential difference due to a Cl -activity change from 11.2 to 112.4 mM [22] was -53.9±0.4 mV (26 microelectrodes). The activity coefficient for Cl -(the ratio between its activity and concentration) is 0.73 [24].…”

A rabbit jejunal isolated enterocyte preparation suitable for transport studies.

“…5) to 216 (Fig. 6) (Lee & Armstrong, 1972;Grasset, Gunter-Smith & Schultz, 1983;Cremaschi, James, Meyer, Rossetti & Smith, 1984). In the context of these comparisons it should be noted that the activity coefficient for K is 0-78 (Robinson & Stokes, 1959).…”

The Presence of NHE1 and NHE3 Na+‐H+ Exchangers and an Apical cAMP‐Independent Cl− Channel Indicate that Both Absorptive and Secretory Functions are Present in Calf Gall Bladder Epithelium

“…The conventional microelectrodes, measurement set-up and acceptance criteria for impalements were similar to those previously described (Henin & Cremaschi, 1975;Cremaschi et al 1984). The microelectrodes had a resistance of 40-70 MΩ, and were connected to a very high input resistance (2 w 10 14 Ω) electrometer (Ketley 617, Cleveland, OH, USA) and a strip chart recorder (Linear 1200, Reno, NV, USA).…”