Myocyte Endothelin Exposure During Cardioplegic Arrest Exacerbates Contractile Dysfunction After Reperfusion

Abstract

Transient left ventricular (LV) dysfunction can occur after cardioplegic arrest. The contributory mechanisms for this phenomenon are not completely understood. We tested the hypothesis that exposure of LV myocytes to endothelin (ET) during simulated cardioplegic arrest would have direct effects on contractile processes with subsequent reperfusion. LV porcine myocytes were randomly assigned to three groups: 1) CONTROL: normothermic (37 degrees C) cell media (n = 204); 2) Cardioplegia: simulated cardioplegic arrest (K(+) 24 mEq/L, 4 degrees C x 2 h) followed by reperfusion and rewarming with cell media (n = 164); and 3) Cardioplegia/ ET: simulated cardioplegic arrest in the presence of ET (200 pM) followed by reperfusion with cell media containing ET (n = 171). Myocyte contractility was measured by computer-assisted video microscopy. In a subset of experiments, myocyte intracellular calcium was determined after Fluo-3 (Molecular Probes, Eugene, OR) loading by digital fluorescence image analysis. Myocyte shortening velocity was reduced after cardioplegic arrest compared with controls (52 +/- 2 vs 84 +/- 3 microm/s, respectively; P < 0.05) and was further reduced with cardioplegic arrest and ET exposure (43 +/- 2 microm/s, P < 0.05). Intracellular calcium was significantly increased in myocytes exposed to cardioplegia compared with normothermic control myocytes and was further augmented by cardioplegia with ET supplementation (P < 0.05). Exposure of the LV myocyte to ET during cardioplegic arrest directly contributed to contractile dysfunction after reperfusion. Moreover, alterations in intracellular calcium may play a role in potentiating the myocyte contractile dysfunction associated with ET exposure during cardioplegic arrest.

Protein Kinase C Isoform Activation and Endothelin-1 Mediated Defects in Myocyte Contractility After Cardioplegic Arrest and Reperfusion

“…[5][6][7] Myocyte function was measured under normothermic conditions or after simulated CA in the presence and absence of ET-1. In addition, these measurements were performed after incubation with inhibitors of specific PKC isoforms.…”

“…Myocytes were isolated from the left ventricular free wall of pigs (Hambone Farms, Orangeburg, SC) (Yorkshire; n ϭ22; 25 to 30 kg) using collagenase digestion. [5][6][7] Viable myocytes, as described previously [5][6][7] (yield Ͼ60%), were plated onto coverslips previously coated with a basement membrane substrate (Matrigel, Collaborative Research Inc). These were stabilized at 37°C in oxygenated media for 60 minutes and then randomized to the experimental protocols described below.…”

“…[2][3][4] Moreover, elevated ET-1 levels in patients during and after cardiac surgery requiring CA may contribute to a complex postoperative course. 3 Although the effects of ET-1 on LV pump function after CA are likely to be multifactorial, ET-1 has been demonstrated to modulate myocyte contractile function, [5][6][7] which in turn can influence LV function. Accordingly, the overall goal of this study was to identify specific components of ET-1-mediated signaling using an isolated myocyte model of simulated CA.…”

Interruption of endothelin signaling modifies membrane type 1 matrix metalloproteinase activity during ischemia and reperfusion

“…Increased synthesis and release of ET has been shown to exacerbate LV pump dysfunction in a number of cardiovascular diseases, particularly with I/R (11,29,46). The diverse physiological actions of ET appear to be mediated through two receptor subtypes, the ET A and ET B receptor.…”

“…For example, cytokines, oxidative stress, and endothelin-1 (ET) have all been demonstrated to change MT1-MMP abundance/activity (9, 16). Increased synthesis and release of ET has been clearly shown to occur in humans and animals with I/R (11,29,46). In vitro, it has been demonstrated that stimulation of isolated LV myocytes with ET significantly increased MT1-MMP abundance by Ͼ40% (9).…”