These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.
Pubmed for Handhelds
PUBMED FOR HANDHELDS
Search MEDLINE/PubMed
Title: Two distinct cytosolic calcium responses to extracellular ATP in rat parotid acinar cells. Author: McMillian MK, Soltoff SP, Cantley LC, Rudel R, Talamo BR. Journal: Br J Pharmacol; 1993 Feb; 108(2):453-61. PubMed ID: 8448596. Abstract: 1. Increasing concentrations of ATP (0.5 microM-300 microM) produced a biphasic increase in intracellular calcium concentration [Ca]i in rat parotid acinar cells, reflecting two distinct Cai responses to extracellular ATP. 2. In the absence of Mg2+ (with 3 mM CaCl2 in the buffer solution), the more sensitive response was maximal at 3-5 microM and was not further increased by 30 microM ATP. This response to ATP was not well maintained and was blocked by ADP (0.5 mM). A second, much larger increase in Cai was observed on addition of 300 microM ATP. This larger effect, which we have described previously, appears to be mediated by ATP4-, and was selectively reversed by 4,4'-di-isothiocyanato-dihydrostilbene-2,2'-disulphonate as well as by high concentrations of alpha,beta-methylene ATP. 3. Among ATP analogues, only the putative P2Z agonist, 3'-0-(4-benzoyl)benzoyl-ATP distinguished between the two responses. This analogue was at least 10 fold more potent than ATP in stimulating the ATP(4-)-response, but did not evoke the more sensitive response. The agonist potency series for both responses to ATP was identical for other analogues examined (ATP > ATP gamma S = 2-methylthio ATP (a P2y-selective agonist) >> ADP, ITP and alpha,beta-methylene ATP (a P2x-selective agonist)). 4. Although the effect of ATP4- could best be characterized as a P2z-type purinoceptor response, this effect was strongly and selectively blocked by reactive blue 2, a putative P2y-purinoceptor antagonist. Reactive blue 2 may bind to and block P2z purinoceptors since [gamma 32P]-ATP binding to parotid cells was inhibited by this compound. 5. In contrast to the response to ATP4-, the more sensitive response to ATP was potentiated by 2+ reactive blue 2 and was less affected by increases in external Mg2+ and Ca2+.6. Parasympathetic denervation selectively increased the more sensitive response, suggesting that it maybe physiologically regulated.[Abstract] [Full Text] [Related] [New Search]