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.
Shitara
Akiko
A
Department of Pharmacology, School of Dentistry, Health Sciences University of Hokkaido, Hokkaido, Japan.
Tanimura
Akihiko
A
Sato
Atsuko
A
Tojyo
Yosuke
Y
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