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Alterations of membrane potential and properties of sarcolemmal vesicles and sarcoplasmic reticulum vesicles in ischemic myocardium
55 LOSS OF CARNITINE FROM THE ISCHEMIC RAT AND CANINE MYOCARDIUM. Dennis J. Paulson, Vera Regitz, and Austin L. University of Wisconsin and Veterans Administration Shug. Hospital, Madison, WI 53705. Changes in tissue carnitine levels were studied in the regional ischemic dog and global ischemic perfused rat heart. Ischemia was induced in dogs by ligating the left anterior descending coronary artery for 3 hrs with and without 1 hr reperfusion. Total carnitine was assayed in the subendoand subepicardium. Esterified carnitine increased with ischemia but no change in total carnitine content was found. With reperfusion a dramatic decrease occured in both layers with the greatest loss from the irreversibly damaged subendocardium. In the perfused rat heart, changes in tissue and perfusion medium carnitine content were measured after a 90% reduction in coronary flow with and without reperfusion. During ischemia, only a small loss of carnitine from tissue into the perfusate was observed. Reperfusion significantly increased this depletion. Carnitine was also lost from the normally working perfused These findings, which show that carnitine is rat heart. lost from both reversibly and irreversibly damaged tissue, suggest that chronic myocardial ischemia may lead to carnitine deficiency of the heart. (Supported by the Research Service of VA Hosptial and NIH HL-17736.)
ALTERATIONS OF lvlEMBRANE POTENTIAL AND PROPERTIES OF SARCOLEMMAL VESICLES AND SARCOPLASMIC RETICULUM VESICLES IN and M.L. Murphy, ISCHEMIC MYOCARDIUlvl. C.F. Peng, K.D. Straub Univ. of Ark. for Med. Sci. ana Medical Research Svc.. VA Medical Center, Little ROCK, AR 72206 Alterations of membrane structure and function may result from a brief period of ischemic insult. This study examines membrane properties of sarcolemmal vesicles (SV) and sarcoplasmic reticulum vesicles (SRV) isolatea from both nonischemic myocardium (NM) and 30-minute ischemic myocaraium IM was produced oy ligating the coronary artery of (IN). swine hearts. SV and SRV were assessed by electron microscopy and enzyme markers. Membrane potential of SV and SRV was determined by using a fluorescent cyanine dye. Ouabain sensitive Na+-K+-ATPase in SV and Ca2+ uptake by SRV were also studied. Results are as follows: (1) Membrane potential of 160 mM KC1 loaded SV and SRV from IM was markedly decreased when compared to membrane potential of SV and SRV from NM. (2) Membrane potential of SV and SRV from NM was gradually decreased by preincubation of those vesicles with Deoxycholate pretreated vesicles 0.1 percent aeoxycholate. behaved like those vesicles isolated from IM. (3) Na+-K+ dependent ATPase of SV ana Ca2+ uptake by SRV from IM also decreased in comparison to those from NM. Results suggest membrane characteristics of SV and SRV were altered in 30 minutes ischemic myocaraium. Alteration of membrane structure (possibly phospholipid components) in SV and SRV from IM may be responsible for the observed decrease in membrane potential.
ALTERATIONS OF lvlEMBRANE POTENTIAL AND PROPERTIES OF SARCOLEMMAL VESICLES AND SARCOPLASMIC RETICULUM VESICLES IN and M.L. Murphy, ISCHEMIC MYOCARDIUlvl. C.F. Peng, K.D. Straub Univ. of Ark. for Med. Sci. ana Medical Research Svc.. VA Medical Center, Little ROCK, AR 72206 Alterations of membrane structure and function may result from a brief period of ischemic insult. This study examines membrane properties of sarcolemmal vesicles (SV) and sarcoplasmic reticulum vesicles (SRV) isolatea from both nonischemic myocardium (NM) and 30-minute ischemic myocaraium IM was produced oy ligating the coronary artery of (IN). swine hearts. SV and SRV were assessed by electron microscopy and enzyme markers. Membrane potential of SV and SRV was determined by using a fluorescent cyanine dye. Ouabain sensitive Na+-K+-ATPase in SV and Ca2+ uptake by SRV were also studied. Results are as follows: (1) Membrane potential of 160 mM KC1 loaded SV and SRV from IM was markedly decreased when compared to membrane potential of SV and SRV from NM. (2) Membrane potential of SV and SRV from NM was gradually decreased by preincubation of those vesicles with Deoxycholate pretreated vesicles 0.1 percent aeoxycholate. behaved like those vesicles isolated from IM. (3) Na+-K+ dependent ATPase of SV ana Ca2+ uptake by SRV from IM also decreased in comparison to those from NM. Results suggest membrane characteristics of SV and SRV were altered in 30 minutes ischemic myocaraium. Alteration of membrane structure (possibly phospholipid components) in SV and SRV from IM may be responsible for the observed decrease in membrane potential.