Simulated ischemia and intracellular pH in isolated ventricular muscle

Abstract

Isolated guinea pig papillary muscles were subjected to an in vitro model of ischemia, consisting of superfusion arrest and immersion in paraffin oil, which results in restriction of substrate supply and metabolite washout. Intracellular pH (pHi) and surface pH (pHs) were measured with glass microelectrodes. Contractile force declined to 82% of the pre-"ischemic" value after 2 min and to 37% of the control value after 10 min. In addition, a shortening of the time to peak and duration of contraction was noted. The rate of force development decreased later than the rate of relaxation. After 10 min, pHi was acidified on average 0.08 pH unit, which is about one-third of the measured pHs change. Tripling the ischemic pHi change by reduction of the intracellular buffering power only slightly increased the rate of tension decline. Experimental pHi changes of similar magnitude, induced during normal superfusion, had a smaller effect on contractile force and failed to reproduce the characteristic changes in time course of the contraction. It is concluded that, in our condition of simulated ischemia, the intracellular acidification cannot account fully for the rapid decline in contractility.

Effects of Stilbene Derivatives SITS and DIDS on Development of Intracellular Acidosis during Ischemia in Isolated Guinea Pig Ventricular Papillary Muscle In Vitro

“…The depolarization in membrane potentials and shortening of APD induced by the present method were in agreement with previous results obtained in the global ischemia for guinea pig (38), porcine (39) and dog heart (40). However, in the present study, intracellular acidification induced by simulated ischemia was greater than that reported by previous authors (32). At this moment, we have no explanation for the discrepancy between the present results and theirs, but the magnitude of intracellular acidification observed in the present study was within the range reported for ischemic myocardium from the normal values of around 7.2 to values as low as 6.3 (41) or even 5.7 (42).…”

“…Furthermore, the present method is suitable for direct microelectrode measurements of cardiac pHl by stable cell impalements. Although simulated ischemia could not bring down muscle surface P02 to anoxic levels, it has been reported that it exerted larger effects on contractility, action potentials and intracellular pH than hypoxic superfusion (32). The depolarization in membrane potentials and shortening of APD induced by the present method were in agreement with previous results obtained in the global ischemia for guinea pig (38), porcine (39) and dog heart (40).…”

“…Isolated guinea pig papillary muscles were superfused in vitro at 36C and subjected to a simulated ischemia, as described by Vanheel et al (32,33). Briefly, an ischemic situation was mimicked by arresting the normal superfusion and removing the Tyrode's solution from the experimental chamber, whereby a thick layer of paraffin oil (about 2 ml), which was present on top of the superfusate, was lowered and settled around the whole muscle.…”

“…In the present study, we employed the model of simulated ischemia that was first described by Vanheel et al (32). An ischemic condition was induced by arresting the normal superfusion and immersing the preparation in mineral oil, which limits the substrate supply to the interstitial fluid and affects the clearance of metabolites.…”

Epi and endomyocardial pH allows the detection of acute right ventricular ischemia in pigs: a new evaluation method

“…4 Interstitial myocardial pH can also be assessed by implanting a small pH electrode in tissue, or by attaching a vacuum-filled Teflon catheter to a mass spectrometer to measure PCO 2 , which correlates with pH. [12][13][14][15] Interstitial myocardial measurements correspond to intracellular myocardial measurements. Brief coronary occlusion reduces interstitial myocardial pH.…”