Extracellular ATP elevates intracellular free calcium in rat parotid acinar cells.
The effect of extracellular ATP on intracellular free Ca2+ was characterized in quin2-loaded parotid acinar cells. ATP specifically increased the intracellular Ca2+ concentration six-fold above a basal level of 180 nM. Of other purine nucleotides tested, only adenylylthiodiphosphate (ATP gamma S) had significant activity. ATP and the muscarinic agonist carbachol increased intracellular Ca2+ even in the absence of extracellular Ca2+. Both agonists stimulated K+ release, which was followed by reuptake of K+, even in the continued presence of agonist. In the absence of Mg2+, ATP was much more potent but no more efficacious in elevating intracellular Ca2+, suggesting that ATP4- is the active species. The effect of ATP was reversed by removal with hexokinase, arguing against a role for an active contaminant of ATP and against a non-specific permeabilizing effect of extracellular ATP. Lactate dehydrogenase release was unaffected by a maximally effective concentration of ATP. These observations are consistent with a possible neurotransmitter role for ATP in the rat parotid gland.
McMillian
M K
MK
Neuroscience Program, Tufts University, Boston, MA 02111.
Soltoff
S P
SP
Cantley
L C
LC
Talamo
B R
BR
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000032:analysis*; D006593:Hexokinase / Q000494:pharmacology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008274:Magnesium / Q000502:physiology; D008297:Male; D010306:Parotid Gland / Q000032:analysis* / Q000166:cytology; D010539:Permeability; D011188:Potassium / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains
D000255:Adenosine Triphosphate; D007770:L-Lactate Dehydrogenase; D006593:Hexokinase; D008274:Magnesium; D011188:Potassium; D002118:Calcium