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)

The effects of substituting gluconate for extracellular Cl, and of treatment with various ion transport blockers, on cytosol pH (pHi) and secretion by the acetylcholine stimulated rat mandibular gland were studied in vitro. Gluconate replacement increased pHi from 7.12 +/- 0.02 to 7.27 +/- 0.04, caused secretory rate to fall by 75%, and increased salivary HCO3 from 14 +/- 0.9 mmol/L to 67 +/- 1.5 mmol/L. Furosemide (1 mmol/L), which blocks Na-K-2Cl symports and Cl-HCO3 antiports, had effects similar to those of gluconate replacement, except that secretion was reduced only by 59%. Bumetanide (1 mmol/L), which blocks only Na-K-2Cl symports, caused a 67% reduction in secretion rate, but it had little effect on pHi and caused only a small rise in salivary HCO3 concentration. SITS (1 mmol/L), which blocks Cl-HCO3 antiports, increased pHi to 7.26 +/- 0.03 and induced a small rise in the secretory rate. Methazolamide and acetazolamide (1 mmol/L), both of which inhibit carbonic anhydrase and may also block anion channels, increased pHi to 7.43 +/- 0.02 and 7.20 +/- 0.03, respectively, but had no effect on secretory rate, and reduced salivary HCO3 slightly. Ba (3 mmol/L), tetraethylammonium (10 mmol/L), and decamethonium (5 mmol/L) all caused marked but reversible reductions in secretory rate, consistent with the known actions of these agents on K channels. Ba, however, also appeared to act as a Ca antagonist, an action that it seemed to share with Mn ions (5 mmol/L).(ABSTRACT TRUNCATED AT 250 WORDS)

To assess the importance for transepithelial salt secretion of current flow across the baso-lateral membrane, we studied the effects of ouabain (1 mmol/l), Ba (3 mmol/l) and tetraethylammonium (TEA: 10 mmol/l) on secretion by the acinar (caerulein stimulated) and ductal (secretin stimulated) epithelia of the perfused rat pancreas. Within 10 min, ouabain caused a 79% inhibition of acinar secretion which was resolvable into two exponentials with half-times, respectively, of 0.24 min +/- 0.19 (S.D.) and 6.40 +/- 0.46 min. In contrast, it caused only a monoexponential inhibition of ductal secretion (61% in 10 min) with a half-time of 5.08 +/- 0.26 min. Ba caused a monoexponential inhibition of acinar secretion (70% in 10 min) with a half-time of 1.82 +/- 0.27 min, but it had no inhibitory effect on ductal secretion. The action of TEA was similar to that of Ba: it caused monoexponential inhibition of acinar secretion (26% in 10 min) with a half-time of 1.82 +/- 0.03 min, and it too had no effect on ductal secretion. For comparison, we also studied the effect of these drugs on the more rapidly secreting rat mandibular gland (stimulated with acetylcholine). All three drugs were strongly inhibitory: within 10 min, ouabain caused a 95%, Ba an 89% and TEA an 83% inhibition. The decay curves appeared to be monoexponential with half-times, respectively, of 1.49 +/- 0.12, 0.51 +/- 0.3 and 0.56 +/- 0.02 min.(ABSTRACT TRUNCATED AT 250 WORDS)