{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,20]],"date-time":"2025-10-20T18:33:32Z","timestamp":1760985212046},"reference-count":0,"publisher":"Wiley","issue":"1","license":[{"start":{"date-parts":[[1987,8,1]],"date-time":"1987-08-01T00:00:00Z","timestamp":554774400000},"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":[[1987,8]]},"abstract":"<jats:p>1. We have used laser micromass analysis (l.a.m.m.a.) to investigate Ca uptake and release in intact 'red' rod photoreceptors in the dark\u2010adapted retina of the toad, Bufo marinus. 2. With l.a.m.m.a. it is possible to measure separately the concentrations of each of the Ca isotopes. Rods normally containing almost exclusively 40Ca can be incubated in Ringer solution containing the stable isotopes 42Ca or 44Ca. In this way, the movements of Ca into and out of the rod can be separately determined. 3. When rods are incubated in darkness in high 44Ca (up to 20 mM), large amounts of 44Ca accumulate in the outer segment at a rate which increases with increasing external 44Ca concentration. However, this 44Ca appears not to exchange with the 40Ca originally present within the rod. This result suggests that the 40Ca may be sequestered within a pool which normally exchanges slowly with external Ca. 4. We explored Ca exchange in high\u2010Ca solutions in more detail with double\u2010isotope labelling. In these experiments, rods were first pre\u2010loaded with Ca of one isotope (42Ca) and then incubated in Ringer solution containing another (44Ca). We could then measure separately the rate of exchange of the pre\u2010loaded 42Ca with the 44Ca in the Ringer solution and with the 40Ca originally present within the rod in the sequestered pool. 5. These experiments show that the pre\u2010loaded\u2010Ca exchanges rapidly with Ca in the Ringer solution, at least in part by Ca\u2010Ca exchange, but much more slowly with the Ca originally present within the rod. Thus Ca in the outer segments can exist in (at least) two pools: one which exchanges rapidly across the plasma membrane and is probably Ca free or loosely bound within the cytosol, and another which exchanges slowly and is probably Ca within the disks. 6. Although Ca sequestered within the outer segment normally exchanges quite slowly, it can be rapidly released if the extracellular free Ca is buffered to low levels with EGTA. The rate\u2010limiting step for Ca release under these conditions appears not to be Na\u2010Ca exchange, since the rate of Ca efflux is unchanged if the Na in the Ringer solution is substituted with choline. 7. Ca can also be released from the sequestered pool if rods are incubated in Ringer solution containing 100 or 500 microM\u2010IBMX (3\u2010isobutyl\u20101\u2010methylxanthine).(ABSTRACT TRUNCATED AT 400 WORDS)<\/jats:p>","DOI":"10.1113\/jphysiol.1987.sp016661","type":"journal-article","created":{"date-parts":[[2014,12,19]],"date-time":"2014-12-19T06:40:11Z","timestamp":1418971211000},"page":"361-384","source":"Crossref","is-referenced-by-count":14,"title":["Calcium in dark\u2010adapted toad rods: evidence for pooling and cyclic\u2010guanosine\u20103'\u20105'\u2010monophosphate\u2010dependent release."],"prefix":"10.1113","volume":"389","author":[{"given":"G L","family":"Fain","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"W H","family":"Schr\u00f6der","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[1987,8]]},"container-title":["The Journal of Physiology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/api.wiley.com\/onlinelibrary\/tdm\/v1\/articles\/10.1113%2Fjphysiol.1987.sp016661","content-type":"unspecified","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/physoc.onlinelibrary.wiley.com\/doi\/pdf\/10.1113\/jphysiol.1987.sp016661","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,10,21]],"date-time":"2023-10-21T01:19:07Z","timestamp":1697851147000},"score":1,"resource":{"primary":{"URL":"https:\/\/physoc.onlinelibrary.wiley.com\/doi\/10.1113\/jphysiol.1987.sp016661"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1987,8]]},"references-count":0,"journal-issue":{"issue":"1","published-print":{"date-parts":[[1987,8]]}},"alternative-id":["10.1113\/jphysiol.1987.sp016661"],"URL":"https:\/\/doi.org\/10.1113\/jphysiol.1987.sp016661","archive":["Portico"],"relation":{},"ISSN":["0022-3751","1469-7793"],"issn-type":[{"value":"0022-3751","type":"print"},{"value":"1469-7793","type":"electronic"}],"subject":[],"published":{"date-parts":[[1987,8]]}}}