{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,28]],"date-time":"2026-09-28T17:49:04Z","timestamp":1790617744734,"version":"4.1.0"},"reference-count":0,"publisher":"Ovid Technologies (Wolters Kluwer Health)","issue":"1","content-domain":{"domain":["www.ahajournals.org"],"crossmark-restriction":true},"short-container-title":["Circulation Research"],"published-print":{"date-parts":[[1993,7]]},"abstract":"<jats:p>The patch-clamp technique was used to examine the sensitivity of delayed rectifier K+ channels to changes in intracellular divalent cations (Mg2+ and Ca2+). During voltage-step and ramp depolarizations, a delayed rectifier K+ current (IK(dr)) was identified in renal, pulmonary, coronary, and colonic smooth muscle cells as a low-noise outward current that activated near -40 mV, was sensitive to 4-aminopyridine (4-AP), and was insensitive to charybdotoxin. During whole-cell voltage-clamp experiments in each of the cell types, the 4-AP-sensitive IK(dr) was significantly less in cells dialyzed with 10 mM Mg2+ as compared with cells in which no Mg2+ was added to the internal dialysis solution (P &lt; or = .05, n &gt; or = 4). In coronary artery cells, 100 microM 2-(2-aminoethyl)pyridine (an H1 receptor agonist) or 10 microM ryanodine, agents that cause an increase in [Ca2+]i, also caused a significant reduction of the 4-AP-sensitive IK(dr) similar to that produced by Mg2+. 4-AP (5 mM) significantly depolarized single renal arterial cells that were dialyzed with Mg(2+)-free solution but not those dialyzed with 10 mM Mg2+ (P &lt; .01, n = 4). In inside-out patches of renal arterial smooth muscle cells, with 200 nM charybdotoxin in the patch pipette to block large conductance Ca(2+)-activated K+ channels, a 59 +\/- 10-picosiemen K+ channel that was sensitive to cytoplasmic Mg2+ was identified. In Mg(2+)-free solution, channel open probability was 0.028 +\/- 0.012 (n = 8) and 0.095 +\/- 0.011 (n = 8) at +40 and +80 mV, respectively. When the bath solution was changed to one containing 5 or 15 mM Mg2+, channel open probability was significantly reduced by 66% and 68% (+40 mV) or 93% and 96% (+80 mV), respectively. This decrease in the open probability of the delayed rectifier K+ channel resulted from a concentration- and voltage-dependent decrease in mean open time. At +40 mV, time constants for the open time distribution were significantly decreased from 5.5 +\/- 0.52 to 1.2 +\/- 0.14 milliseconds, whereas the closed time constant was significantly increased from 634 +\/- 11.1 to 820 +\/- 14.4 milliseconds (P &lt; .01, n = 4). It is concluded that a 4-AP-sensitive delayed rectifier K+ channel in both vascular and visceral smooth muscle cells is modulated by changes in intracellular Ca2+ and Mg2+ that may alter membrane potential and the contractile state of smooth muscle.<\/jats:p>","DOI":"10.1161\/01.res.73.1.24","type":"journal-article","created":{"date-parts":[[2012,6,12]],"date-time":"2012-06-12T00:47:05Z","timestamp":1339462025000},"page":"24-34","update-policy":"https:\/\/doi.org\/10.1161\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":49,"title":["Intracellular divalent cations block smooth muscle K+ channels."],"prefix":"10.1161","volume":"73","author":[{"given":"C H","family":"Gelband","sequence":"first","affiliation":[{"name":"Department of Physiology, University of Nevada School of Medicine, Reno 89557-0046."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"T","family":"Ishikawa","sequence":"additional","affiliation":[{"name":"Department of Physiology, University of Nevada School of Medicine, Reno 89557-0046."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"J M","family":"Post","sequence":"additional","affiliation":[{"name":"Department of Physiology, University of Nevada School of Medicine, Reno 89557-0046."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"K D","family":"Keef","sequence":"additional","affiliation":[{"name":"Department of Physiology, University of Nevada School of Medicine, Reno 89557-0046."}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"J R","family":"Hume","sequence":"additional","affiliation":[{"name":"Department of Physiology, University of Nevada School of Medicine, Reno 89557-0046."}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"276","container-title":["Circulation Research"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.ahajournals.org\/doi\/pdf\/10.1161\/01.RES.73.1.24","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2024,5,12]],"date-time":"2024-05-12T20:32:56Z","timestamp":1715545976000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.ahajournals.org\/doi\/10.1161\/01.RES.73.1.24"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1993,7]]},"references-count":0,"journal-issue":{"issue":"1","published-print":{"date-parts":[[1993,7]]}},"alternative-id":["10.1161\/01.RES.73.1.24"],"URL":"https:\/\/doi.org\/10.1161\/01.res.73.1.24","relation":{},"ISSN":["0009-7330","1524-4571"],"issn-type":[{"value":"0009-7330","type":"print"},{"value":"1524-4571","type":"electronic"}],"subject":[],"published":{"date-parts":[[1993,7]]},"assertion":[{"value":"1993-07-01","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}]}}