{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,29]],"date-time":"2026-09-29T21:49:55Z","timestamp":1790718595130,"version":"4.1.0"},"reference-count":55,"publisher":"American Physiological Society","issue":"5","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["American Journal of Physiology-Heart and Circulatory Physiology"],"published-print":{"date-parts":[[2012,3,1]]},"abstract":"<jats:p>The ventricular action potential (AP) is characterized by a fast depolarizing phase followed by a repolarization that displays a second upstroke known as phase 2. This phase is generally not present in mouse ventricular myocytes. Thus we performed colocalized electrophysiological and optical recordings of APs in Langendorff-perfused mouse hearts founding a noticeable phase 2. Ryanodine as well as nifedipine reduced phase 2. Our hypothesis is that a depolarizing current activated by Ca<jats:sup>2+<\/jats:sup>released from the sarcoplasmic reticulum (SR) rather than the \u201celectrogenicity\u201d of the L-type Ca<jats:sup>2+<\/jats:sup>current is crucial in the generation of mouse ventricular phase 2. When Na<jats:sup>+<\/jats:sup>was partially replaced by Li<jats:sup>+<\/jats:sup>in the extracellular perfusate or the organ was cooled down, phase 2 was reduced. These results suggest that the Na<jats:sup>+<\/jats:sup>\/Ca<jats:sup>2+<\/jats:sup>exchanger functioning in the forward mode is driving the depolarizing current that defines phase 2. Phase 2 appears to be an intrinsic characteristic of single isolated myocytes and not an emergent property of the tissue. As in whole heart experiments, ventricular myocytes impaled with microelectrodes displayed a large phase 2 that significantly increases when temperature was raised from 22 to 37\u00b0C. We conclude that mouse ventricular APs display a phase 2; however, changes in Ca<jats:sup>2+<\/jats:sup>dynamics and thermodynamic parameters also diminish phase 2, mostly by impairing the Na<jats:sup>+<\/jats:sup>\/Ca<jats:sup>2+<\/jats:sup>exchanger. In summary, these results provide important insights about the role of Ca<jats:sup>2+<\/jats:sup>release in AP ventricular repolarization under physiological and pathological conditions.<\/jats:p>","DOI":"10.1152\/ajpheart.00524.2011","type":"journal-article","created":{"date-parts":[[2011,12,24]],"date-time":"2011-12-24T04:51:40Z","timestamp":1324702300000},"page":"H1160-H1172","source":"Crossref","is-referenced-by-count":23,"title":["Intracellular Ca<sup>2+<\/sup>release underlies the development of phase 2 in mouse ventricular action potentials"],"prefix":"10.1152","volume":"302","author":[{"given":"Marcela","family":"Ferreiro","sequence":"first","affiliation":[{"name":"Biological Engineering and Small Scale Technologies Program, School of Engineering, University of California, Merced, California"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Azad\u00e9 D.","family":"Petrosky","sequence":"additional","affiliation":[{"name":"Biological Engineering and Small Scale 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