{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,12]],"date-time":"2026-03-12T04:48:53Z","timestamp":1773290933149,"version":"3.50.1"},"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. Relationships between cytosolic Ca2+ concentration ([Ca2+]cyt), myosin light chain (MLC) phosphorylation and muscle tension were examined in circular smooth muscle of canine gastric antrum. 2. Electrical slow waves induced a transient increase in [Ca2+]cyt and muscle tension. [Ca2+]cyt increased before the initiation of contraction and reached a maximum before the peak of the phasic contractions. Following the first Ca2+ transient, a second rise in [Ca2+]cyt was often observed. The second Ca2+ transient was of similar magnitude to the first, but only in some cases was this increase in [Ca2+]cyt associated with a second phase of contraction. Relaxation occurred more rapidly than the restoration of resting levels of [Ca2+]cyt. 3. Acetylcholine (ACh; 3 x 10(\u20107) M) increased the amplitude of Ca2+ transients, caused MLC phosphorylation and increased the force of contraction. The decay of contraction and MLC dephosphorylation preceded that of [Ca2+]cyt. 4. Increasing external K+ (to 25\u201040 mM) caused a sustained increase in [Ca2+]cyt, but little change in resting tension. This suggests that the Ca2+ sensitivity decreased as [Ca2+]cyt increased. Increasing K+ to 59.5 mM further increased the level of [Ca2+]cyt, induced MLC phosphorylation and caused a transient contraction. When normal levels of K+ were restored, the rates of MLC dephosphorylation and relaxation exceeded the rate of decay in [Ca2+]cyt. 5. Removal of external Ca2+ in depolarized muscles decreased [Ca2+]cyt below the resting level without affecting resting tension. Readmission of Ca2+ to depolarized muscles caused force to develop at [Ca2+]cyt levels below the original resting level, suggesting that Ca2+ sensitivity was increased when the resting level of [Ca2+]cyt was decreased. 6. The phosphatase inhibitor, calyculin\u2010A (10(\u20106) M), induced tonic contraction and MLC phosphorylation without an increase in [Ca2+]cyt. During these contractures, electrical activity caused transient increases in [Ca2+]cyt and phasic contractions which were superimposed upon the Ca(2+)\u2010independent contracture. In the presence of calyculin\u2010A, relaxation occurred in two phases. The initial, rapid phase of relaxation was not significantly affected by calyculin\u2010A, but the slow phase was significantly decreased. 7. These results suggest that the relationship between [Ca2+]cyt, MLC phosphorylation and contraction changes as a function of [Ca2+]cyt in canine antral muscles. This may be due to a Ca(2+)\u2010and time\u2010dependent phosphatase that regulates the level of myosin phosphorylation.<\/jats:p>","DOI":"10.1113\/jphysiol.1991.sp018704","type":"journal-article","created":{"date-parts":[[2014,12,17]],"date-time":"2014-12-17T17:57:08Z","timestamp":1418839028000},"page":"207-224","source":"Crossref","is-referenced-by-count":31,"title":["Time\u2010dependent changes in Ca2+ sensitivity during phasic contraction of canine antral smooth muscle."],"prefix":"10.1113","volume":"440","author":[{"given":"H","family":"Ozaki","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"W T","family":"Gerthoffer","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"N G","family":"Publicover","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"N","family":"Fusetani","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"K M","family":"Sanders","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"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.sp018704","content-type":"unspecified","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/physoc.onlinelibrary.wiley.com\/doi\/pdf\/10.1113\/jphysiol.1991.sp018704","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,10,23]],"date-time":"2023-10-23T00:39:16Z","timestamp":1698021556000},"score":1,"resource":{"primary":{"URL":"https:\/\/physoc.onlinelibrary.wiley.com\/doi\/10.1113\/jphysiol.1991.sp018704"}},"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.sp018704"],"URL":"https:\/\/doi.org\/10.1113\/jphysiol.1991.sp018704","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]]}}}