Intracellular pH in the rat mandibular salivary gland: the role of Na?H and Cl?HCO3 antiports in secretion

Abstract

Intracellular pH (pHi) in the perfused rat mandibular gland was determined from the distribution of DMO (5,5-dimethyl-2,4-oxazolidinedione). In unstimulated glands, pHi averaged 7.12 +/- 0.02. Stimulation with a "standard" (submaximal) concentration (0.3 mumol/l) of acetylcholine (ACh) caused a fall in pHi to 6.81 +/- 0.06 over 60 min, but a maximal concentration (1.0 mumol/l) caused an initial rise in pHi to 7.60 +/- 0.02, followed by a fall to 7.45 +/- 0.02 over 60 min. After replacement of perfusate Cl with gluconate, the standard ACh concentration caused a rise in pHi to 7.50 +/- 0.02 followed by a fall to 7.27 +/- 0.04 after 60 min, concomitant with a 76% fall in secretory rate and a rise in salivary HCO3 concentration from 14 +/- 0.9 to 67 +/- 1.5 mmol/l. Furosemide (1 mmol/l) had a similar effect to gluconate replacement except that secretory rate fell only by 60%. Bumetanide (1 mmol/l), which inhibited secretion by 67%, did not cause pHi to rise following ACh stimulation but prevented the fall seen with ACh alone. Acetazolamide and methazolamide (1 mmol/l) had no effect on the salivary secretory response to ACh but they caused pHi to rise, respectively, to 7.20 +/- 0.03 and 7.43 +/- 0.02. Bumetanide and methazolamide together caused pHi to rise to 7.58 +/- 0.02 and reduced the secretory response to ACh by 91%. The disulfonic stilbene, SITS, caused pHi to rise to 7.26 +/- 0.03. Ouabain and amiloride both caused resting pHi to fall closer to equilibrium and largely abolished the gland's responsiveness to ACh.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of Carbonic Anhydrase Accounts for the Direct Vascular Effects of Hydrochlorothiazide

“…In agreement with our findings, acetazolamide has also been reported to increase pH i in turtle bladder cells, 18 kidney cells, 19 choroid plexus epithelial cells, 20 and the mandibular gland. 21 Under different conditions and in different cells, acetazolamide has also been reported to decrease 22 or have no effect 23 on pH i . The mechanism of action of the acetazolamide-induced rise in pH i is not completely understood, but most reports focus on an intracellular accumulation of HCO 3 24,25 due to inhibition of Cl/HCO 3 exchange.…”

Cellular Mechanisms Underlying the Production of Primary Secretory Fluid in Salivary Glands

“…Stimulation alters intracellular pH in salivary cells 62 and cell volume regulation in other cells 1617 involves the activation of ion movements which allow the cell to maintain a stable volume in the presence of significant transcellular flows of ion and water. Volume regulatory mechanisms are more clearly seen in epithelial 71 and other cells 1617 after exposure to solutions of low or high osmolarity.…”

“…Measurements of cell pH in salivary glands suggest that the cells spend metabolic energy to eliminate protons from the cytosol and to maintain pH (and HCO 3 concentration) above equilibrium. 62 Stimulation with acetylcholine causes changes in cell pH of rat submandibular glands which vary according to the dose. A submaximal dose causes a fall in pH while a supramaximal dose has a biphasic effect involving first an increase in cell pH and a slower fall.…”

“…A submaximal dose causes a fall in pH while a supramaximal dose has a biphasic effect involving first an increase in cell pH and a slower fall. 62 Use of ion substitutions and transport inhibitors suggested that stimulation activates the Na/H antiport, whose presence is normally obscured by the activity of the C1/HCO 3 antiport. 62 Recent evidence from our laboratory has shown that rat submandibular acini exposed to NH 4 C1 (which should cause intracellular acidification) show increased rates of uptake of the isotopic tracer 22 Na.…”

Immunohistochemical Identification of Type B Intercalated Cells in the Rat Kidney by a Monoclonal Antibody.

“…This idea is supported by the cellular distribution of the immunoreactivity with OS-3 outside of the kidney. Intense and selective immunoreactivity with OS-3 was found in the epithelium of the pancreatic excretory duct, and glandular cells in the pyloric, duodenal and salivary glands, all of which are HC03--secreting tissues (KIRKEGAARD et al, 1984;STIEL et al, 1984;PIRANI et al, 1987;LEE and TURNER, 1991;RAEDER, 1992;VILLANGER et al, 1995). Furthermore, the subcellular localization was essentially identical among the epithelial and glandular cells: the major site of localization was the basolateral or lateral membrane characterized by an aggregation of microvilli.…”