Pretreatment with XXXX (T3). Effects on myocyte contractile function after hypothermic @entity1167 and rewarming.

@entity1707 @entity1167 @entity3044 @entity6564 @entity1954 @entity6143
Circulating levels of @entity6143 are depressed after cardiopulmonary bypass and have been implicated to play a contributory role in the alterations in left ventricular function after hypothermic @entity1167 and rewarming. The central hypothesis of the present study was that pretreatment of isolated myocytes with @entity1954 will have a direct and beneficial effect on contractile performance after hypothermic @entity1167 and rewarming. Contractile function in isolated @entity1707 left ventricular myocytes was examined by video microscopy after the following treatment protocols: (1) 37 degrees C incubation in medium (normothermia) for 2 hours with @entity1954 followed by a 2-hour normothermic incubation with no @entity1954 , (2) 4 hours of normothermic incubation with no @entity1954 , (3) normothermic incubation for 2 hours with @entity1954 followed by 2 hours of @entity6564 , hypothermic @entity1167 ([K+]:24 mmol/L; 4 degrees C) and subsequent rewarming, and (4) normothermic incubation for 2 hours with no @entity1954 followed by 2 hours of @entity6564 , hypothermic @entity1167 and rewarming. Two hours of normothermia with @entity1954 increased myocyte contractile function by 30% compared with values in untreated control myocytes, and this increase persisted after a subsequent 2-hour incubation under normothermic conditions with no @entity1954 . For example, myocyte velocity of shortening in @entity1954 -pretreated myocytes was 84 +/- 4.9 microns/sec compared with 62 +/- 2.8 microns/sec in control myocytes (p < 0.05). @entity1167 and subsequent rewarming caused a significant reduction in myocyte velocity of shortening from normothermic values (37 +/- 3.4 microns/sec, p < 0.05). However, in myocytes pretreated with @entity1954 , myocyte contractile function was significantly higher after hypothermic @entity1167 and rewarming (54 +/- 2.5 microns/sec, p < 0.05). In a second series of experiments, beta-adrenergic responsiveness was examined after pretreatment with @entity1954 . In the presence of the beta-adrenergic agonist @entity3044 (25 nmol/L), myocyte contractile function was increased by 26% in the @entity1954 -treated myocytes compared with that in untreated control myocytes. This enhanced beta-adrenergic responsiveness with @entity1954 pretreatment persisted with subsequent exposure to hypothermic @entity1167 and rewarming. In summary, @entity1954 pretreatment caused an increase in myocyte contractile function and beta-adrenergic responsiveness under normothermic conditions and after hypothermic @entity1167 and rewarming. Thus the present study provides direct evidence to suggest that preemptive treatment with @entity1954 may improve left ventricular contractile performance after hypothermic @entity1167 and rewarming.
