Intracellular pH during secretion in the perfused rabbit mandibular salivary gland measured by31P NMR spectroscopy |
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Authors: | Martin C Steward Yoshiteru Seo R Maynard Case |
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Institution: | (1) Department of Physiological Sciences, University of Manchester, Stopford Building, M13 9PT Manchester, UK;(2) Present address: Department of Molecular Physiology, National Institute for Physiological Sciences, 444 Okazaki, Japan |
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Abstract: | Intracellular pH (pHi) was measured in the isolated, perfused rabbit mandibular salivary gland by31P NMR spectroscopy. In the unstimulated gland perfused with HCO
3
–
/CO2-buffered Ringer's solution, pHi was 7.27±0.01. Continuous stimulation with acetylcholine elicited dose- and time-dependent changes in pHi. 10–6 mol/l acetylcholine caused a brief intracellular acidosis (–0.19±0.06 pH units) followed by an increase in pHi to a more alkaline steady-state value (7.33±0.02). In the absence of perfusate HCO
3
–
or in the presence of 10–4 mol/l DIDS (4,4 -diisothiocyanatostilbene-2,2 -disulphonic acid), the transient acidosis was abolished and pHi increased rapidly to give a sustained alkalosis (7.49±0.03 and 7.44±0.03 respectively). In the presence of 10–3 mol/l amiloride, the response to acetylcholine was a rapid decrease in pHi to 7.02±0.02. The data suggest that, during perfusion with HCO
3
–
/CO2-buffered solutions, stimulation with acetylcholine results in a transient loss of HCO
3
–
from the acinar cells (causing a transient acidosis), and, independently, the activation of Na+–H+ exchange (causing a sustained alkalosis). In the unstimulated gland, DIDS and the HCO
3
–
-free perfusate caused decreases in pHi to 7.12±0.02 and 7.04±0.01 respectively. In contrast, amiloride had little effect. The relatively high value of pHi maintained by the unstimulated gland is therefore probably not due to Na+–H+ exchange. |
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Keywords: | Salivary gland Intracellular pH 31P NMR spectroscopy Acetylcholine Amiloride DIDS Na+– H+ exchange |
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