1,721,014 research outputs found
Intracellular potassium activity in epithelial cells of frog fundic gastric mucosa.
No full textMicroelectrodes were used to measure membrane potential and intracellular potassium activity in surface epithelial cells (SEC) of frog (Rana esculenta) fundic gastric mucosa in vitro. Separate measurements were carried out by applying fine-tipped, single barrelled, KCl filled non-selective electrodes and liquid K+ -selective electrodes. Membrane potentials with respect to the mucosal and serosal surfaces, measured with non-selective electrodes, were -54.5 +/- 1.0 S.E mV (n = 59) and -73.0 +/- 1.1 S.E. mV (n = 59) respectively. The electrical potential difference referred to the mucosal surface, when measured with K+ -sensitive electrodes, was +21.2 +/- 0.8 S.E mV (n = 35), and intracellular K+ activity was 98.5 mmol/l. Assuming that intracellular and extracellular K+ activity coefficients are equal (gamma K = gamma K), the K+ concentration is 135.0 mmol/l. The K+ equilibrium potential, EK, was calculated as -90. mV i.e. more negative than both membrane potentials. This result indicates active potassium accumulation in the SEC and provides direct evidence of the presence of an active K+ pump in either both or in only one of the cell membrane
Effect of external sodium on intracellular chloride activity in the surface cells of frog gastric mucosa. Microelectrode studies
No full textEffect of histamine on the basolateral K+ conductance of frog stomach oxyntic cells and surface epithelial cells
No full textDirect pH microelectrode measurement of acid and alkaline secretion in glands of frog gastric mucosa
No full textGastric gland secretory properties have been studied by a new approach that allows the gland lumen pH (pHgl) to be measured with double-barrelled microelectrodes in isolated intact gastric mucosa perfused in vitro. After puncturing an oxyntic cell (OC) from the serosal surface, the microelectrode tip was advanced towards the gland lumen until the electrical recordings became equal to transepithelially measured potential (Vt) and resistance (Rt) values. In 15 resting mucosae (0.1 mM cimetidine) perfused on either surface with HCO3 Ringer solution, Vt and Rt were -20.7 SE ± 2.3 mV and 428 ± 52 Ω·cm2, respectively; pHgl was 7.68 ± 0.09, a value significantly higher (p<0.05) than solution (pH 7.48). Perfusion of the lumen with HCO3-free buffer solutions (pH between 6.4 and 8.4) produced corresponding changes of pHgl indicating that the luminal perfusate has relatively fast access to the gland lumen (90% of the maximum value was reached within 5 min). Following stimulation with histamine (0.5 mM) pHgl became progressively acidic and reached values between 5.3 and 2.2 within 30 min (n=8). On the other hand, stimulation with carbachol (0.1 mM) in presence of cimetidine. significantly alkalinized the gland lumen by 0.11 ± 0.02 pH units (n=11; p<0.001). The latter data support our recent findings that OC are able to secrete bicarbonate under carbachol stimulation. The fact that in resting state pHgl is higher than the pH of Ringer solution suggests that OC participate also to basal alkaline secretion
Comparison of the basolateral K+ conductance of frog stomach oxyntic and surface epithelial cells at rest and after stimulation with histamine
No full textHistamine reduces Cl activity in surface epithelial cells of frog gastric mucosa. Suggestive evidence for ionic coupling beween surface epithelial and oxyntic cells
No full textMicroelectrode determination of oxyntic cell pH in intact frog gastric mucosa. Effect of histamine
No full textEvidence for rheogenic sodium bicarbonate cotransport in the basolateral membrane of oxyntic cells of frog gastric fundus
No full textEvidence that extracellular calcium can act as a “third messenger” to regulate secretory activity
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