{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,7,7]],"date-time":"2025-07-07T06:29:17Z","timestamp":1751869757215},"reference-count":0,"publisher":"Wiley","issue":"1","license":[{"start":{"date-parts":[[1991,8,1]],"date-time":"1991-08-01T00:00:00Z","timestamp":681004800000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["The Journal of Physiology"],"published-print":{"date-parts":[[1991,8]]},"abstract":"<jats:p>1. Whole\u2010cell patch clamp was combined with microspectrofluometry (Indo\u20101) to study the effects of bath applied ATP on membrane currents and cytoplasmic Ca2+ concentration ([Ca2+]i) in single smooth muscle cells of the guinea\u2010pig urinary bladder. Experiments were carried out at 22 degrees C and in 3.6 mM [Ca2+]o. Superimposed K+ currents were reduced by Cs+ dialysis from the patch electrode. 2. At \u201060 mV, ATP induced an inward current (Ins,ATP) that peaked within 0.4 s and then decayed. Ins,ATP was activated half\u2010maximally by 1.1 microM\u2010ATP and saturated at 50 microM\u2010ATP to \u20101.1 +\/\u2010 0.2 nA (mean +\/\u2010 S.E.M.). At 3.6 mM [Ca2+]o, Ins,ATP had a reversal potential (Erev) of \u20105 +\/\u2010 2 mV. From the shifts in Erev during changes in [Na+]o or [Ca2+]o we estimated that approximately 7% of Ins,ATP is carried by Ca2+ ions. 3. ATP (50 microM) increased [Ca2+]i transiently from resting 130 +\/\u2010 40 nM to 730 +\/\u2010 100 nM. At 22 degrees C, [Ca2+]i rose at a rate proportional to the instantaneous current amplitude of Ins,ATP. This relation was lost, however, after warming to 36 degrees C which increased the peak Ins,ATP (Q10 = 1.25) but reduced the peak of the ATP induced [Ca2+]i transient (Q10 = 0.75). We suggest that warming to 36 degrees C stimulated Ca2+ sequestration and Ca2+ efflux to such a degree that peak [Ca2+]i was attenuated significantly. 4. The contribution of Ca2+ ions to Ins,ATP was evaluated from a comparison of the increments in [Ca2+]i due to Ins,ATP and due to L\u2010type Ca2+ channel current (ICa). For the same increment, Ins,ATP had to transport 19 times more charge than ICa. This number suggests that 5.8 +\/\u2010 0.8% of Ins,ATP is carried by Ca2+ ions which can be translated into a permeability ratio of PNa:PCa approximately 1:1. 5. During bath application of ATP, peak ICa was inhibited by 80 +\/\u2010 15%. Inhibition of ICa diminished to 20 +\/\u2010 8% after cell dialysis with 40 mM\u2010EGTA, and it was 19 +\/\u2010 7% when extracellular Ca2+ had been substituted by Ba2+. These results are in agreement with the hypothesis of \u2018ICa inactivation by Ca2+\u2019. Depletion of intracellular Ca2+ stores by pre\u2010treatment with 20 mM\u2010caffeine did not attenuate significantly the ATP\u2010induced rise in [Ca2+]i or the ATP\u2010induced inhibition of ICa. 6. The ATP\u2010induced [Ca2+]i transients and the reduction of peak ICa recovered along a similar time course.(ABSTRACT TRUNCATED AT 400 WORDS)<\/jats:p>","DOI":"10.1113\/jphysiol.1991.sp018720","type":"journal-article","created":{"date-parts":[[2014,12,17]],"date-time":"2014-12-17T17:57:08Z","timestamp":1418839028000},"page":"479-496","source":"Crossref","is-referenced-by-count":54,"title":["Ca2+ influx through ATP\u2010gated channels increments [Ca2+]i and inactivates ICa in myocytes from guinea\u2010pig urinary bladder."],"prefix":"10.1113","volume":"440","author":[{"given":"P","family":"Schneider","sequence":"first","affiliation":[]},{"given":"H H","family":"Hopp","sequence":"additional","affiliation":[]},{"given":"G","family":"Isenberg","sequence":"additional","affiliation":[]}],"member":"311","published-online":{"date-parts":[[1991,8]]},"container-title":["The Journal of Physiology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/api.wiley.com\/onlinelibrary\/tdm\/v1\/articles\/10.1113%2Fjphysiol.1991.sp018720","content-type":"unspecified","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/physoc.onlinelibrary.wiley.com\/doi\/pdf\/10.1113\/jphysiol.1991.sp018720","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,10,23]],"date-time":"2023-10-23T00:38:53Z","timestamp":1698021533000},"score":1,"resource":{"primary":{"URL":"https:\/\/physoc.onlinelibrary.wiley.com\/doi\/10.1113\/jphysiol.1991.sp018720"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1991,8]]},"references-count":0,"journal-issue":{"issue":"1","published-print":{"date-parts":[[1991,8]]}},"alternative-id":["10.1113\/jphysiol.1991.sp018720"],"URL":"https:\/\/doi.org\/10.1113\/jphysiol.1991.sp018720","archive":["Portico"],"relation":{},"ISSN":["0022-3751","1469-7793"],"issn-type":[{"value":"0022-3751","type":"print"},{"value":"1469-7793","type":"electronic"}],"subject":[],"published":{"date-parts":[[1991,8]]}}}