Microfluorometric studies of intracellular Ca2+ and Na+ concentrations in normal human labial gland acini.
The responses of human labial salivary acini to muscarinic, adrenergic, and substance P peptidergic stimulation were studied using the fluorescent indicators fura 2 for intracellular Ca2+ concentration ([Ca2+]i) and sodium-binding benzofuran isophthalate for intracellular Na+ concentration ([Na+]i). Of the agents tested (carbachol, epinephrine, isoproterenol, and substance P) only the muscarinic agonist carbachol increased [Ca2+]i substantially above basal levels (three to fourfold; half-maximal effect approximatley 1 microM). Experiments with the Ca(2+)-adenosinetriphosphatase inhibitor thapsigargin indicated the presence of both thapsigargin-sensitive and thapsigargin-insensitive intracellular Ca2+ stores, both of which were mobilized by carbachol. [Na+]i in resting labial acini was approximately 20 mM. On stimulation with carbachol, [Na+]i rose transiently to more than three times this value and then partially recovered. This carbachol-induced rise in [Na+]i was largely blocked by bumetanide, a specific inhibitor of the Na(+)-K(+)-2Cl- cotransporter. These results are consistent with an intact muscarinic fluid secretory response in human labial acini with transepithelial Cl- secretion driven via Na(+)-K(+)-2Cl- cotransport and the secretion of fluid presumably following Cl- loss via an apical Ca(2+)-dependent anion channel, as observed in salivary acini from other species.
Valdez
I H
IH
Clinical Investigations and Patient Care Branch, National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland 20892.
Paulais
M
M
Fox
P C
PC
Turner
R J
RJ
D000328:Adult; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D005260:Female; D005470:Fluorometry; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism*; D008046:Lip; D008297:Male; D008875:Middle Aged; D009994:Osmolar Concentration; D012016:Reference Values; D012470:Salivary Glands, Minor / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D013268:Stimulation, Chemical
D002217:Carbachol; D012964:Sodium; D002118:Calcium