Spontaneous Ca2+ oscillations via purinergic receptors elicit transient cell swelling in rat parotid ducts.
Rat parotid ductal cells were found to exhibit spontaneous Ca(2+) oscillations. These oscillatory Ca(2+) responses were observed during continuous perfusion with physiological salt solution at 37 degrees C in the absence of calcium mobilizing agonist stimulation. These Ca(2+) oscillations were completely blocked by the purinergic receptor inhibitors, pyridoxal phosphate-6-azo (benzene-2,4-disulfonic acid) (PPADS) and suramin, but were not blocked by the muscarinic antagonist, atropine, nor the alpha-adrenergic antagonist, phentolamine. Simultaneous observation with fura-2 fluorescence and differential interference contrast (DIC) images showed that the spontaneous elevations of [Ca(2+)]i were well correlated with the shape changes of the ductal cells. Using a plasma membrane fluorescence probe, we found that the changes in DIC images reflected spontaneous cell swelling of ductal cells. Electron microscopic analysis after Ca(2+) imaging indicated that the spontaneously oscillating duct cells contained numerous granules at the luminal side, which is characteristic of the granular duct cells. These results indicate that the spontaneous [Ca(2+)]i increase occurs through purinergic receptors, and activates Ca(2+)-dependent ion transporters and/or channels. Our findings present the possibility that spontaneous Ca(2+) oscillations via purinergic receptors are involved in the regulation of the electrolyte composition of saliva in resting states.
Department of Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan.
Akiko
A
Shitara
Akihiko
A
Tanimura
Atsuko
A
Sato
Yosuke
Y
Tojyo
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004573:Electrolytes / Q000378:metabolism; D006984:Hypertrophy / Q000378:metabolism; D010306:Parotid Gland / Q000378:metabolism* / Q000473:pathology*; D058914:Purinergic Antagonists; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D011983:Receptors, Purinergic / Q000187:drug effects / Q000378:metabolism*; D013498:Suramin / Q000494:pharmacology
D004573:Electrolytes; D058914:Purinergic Antagonists; D011983:Receptors, Purinergic; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D013498:Suramin; D000255:Adenosine Triphosphate; D002118:Calcium