AJP - Gastrointestinal and Liver Physiology, Vol 253, Issue 3 290-G297, Copyright © 1987 by American Physiological Society
Stimulation-induced changes in cytosolic calcium in rat parotid acini
B. Nauntofte and S. Dissing
The concentration of cytosolic, free calcium (Ca2+i) in
collagenase-isolated rat parotid acini was measured by use of the
fluorescent dye fura-2 (G. Grynkiewicz, M. Poenie, and R. Y. Tsien, J.
Biol. Chem. 260: 3440-3450, 1985). Ca2+i was measured in unstimulated acini
and in acini stimulated with cholinergic, alpha-adrenergic, and
beta-adrenergic agonists, respectively. In unstimulated acini suspended in
1 mM Ca media, Ca2+i amounted to 155 +/- 38 nM (mean +/- SD, n = 14). After
stimulation with the cholinergic agonist carbachol, Ca2+i increased
transiently with a peak value of 640 +/- 90 nM (n = 3) obtained 4-6 s after
stimulation. The peak value of Ca2+i was reduced when the extracellular
calcium concentration decreased, and at 2 nM external calcium, Ca2+i
amounted to 50% of the peak value observed at 1 mM external calcium. It was
calculated that at least 50% of the rise in Ca2+i observed under
physiological conditions (1 mM external calcium) after cholinergic
stimulation is due to calcium mobilizations from intracellular pools.
Stimulation with the nonspecific adrenergic agonist adrenaline caused a
rise in Ca2+i of a similar magnitude as the rise observed after cholinergic
stimulation. However, stimulations with the alpha-adrenergic agonist
phenylephrine and the beta-adrenergic agonist isoproterenol caused a rise
in Ca2+i amounting to 60 and 10%, respectively, of the rise observed after
cholinergic or adrenergic stimulation.
