Tracer kinetics analysis of the extracellular spaces in saline perfused hearts.

BACKGROUND: Precise estimation of the cellular water content presupposes a correct definition of the water fraction in tissue extracellular space. Low molecular weight markers (LMM), such as sulphate ion and sucrose, are widely used to define extracellular space size despite indications that they penetrate the cell. In contrast, inulin, with molecular weight of about 5000, is commonly regarded as a cell impermeable extracellular marker. OBJECTIVES: To compare LMM with inulin as markers in determining extracellular space size. ANIMALS AND METHODS: The size of extracellular space in guinea pig hearts perfused with crystalloid solution (hydrated hearts) was determined morphometrically and by mathematical model analysis of washout kinetics of LMM ((35)SO(4), (14)C-sucrose) or (3)H-inulin. RESULTS: Morphometrically, the sizes of vascular and interstitial spaces in the hydrated hearts were estimated to be 102+/-8 mL/kg wet mass (wm) and 452+/-17 mL/kg wm, respectively. Comparable data were obtained from model simulation of tracer washout: 67 mL/kg wm for vascular space and 439 to 462 mL/kg wm for interstitial space. Tracer penetration into cellular water, as shown by model analysis, was 28% for LMM and, reported here for the first time, 18% for inulin. The observed edema was probably due entirely to fluid accumulation in the interstitial space. CONCLUSION: Intracellular penetration of LMM must be taken into account, especially in modern nuclear magnetic resonance spectroscopic methods of cellular water monitoring in isolated perfused hearts.

Dependence of the cardiac contractile force on the coronary perfusion pressure: difference between the isovolumic hearts of rat and guinea pig.

We have compared the contractile responses of the isovolumic hearts of rat and guinea pig to a rise in the coronary perfusion pressure in the range 60-120 mmHg (Gregg's phenomenon). Left ventricular systolic pressure was lower in guinea pig hearts than in rat hearts at a low coronary perfusion pressure and increased markedly less at a higher perfusion pressure, despite a greater increase in coronary flow. The rise in left ventricular systolic pressure in the guinea pig hearts was entirely due to an increased left ventricular end-diastolic pressure, while left ventricular developed pressure did not increase. The wet weight of the hearts in situ was similar in both species, but after perfusion the guinea pig hearts gained significantly more fluid than the rat hearts (65% of the initial heart weight compared to 37%). The group of rat hearts perfused with a low external concentration of Ca2+ developed a similar left ventricular pressure to the guinea pig hearts and gained a similar amount of fluid (63%), but Gregg's phenomenon was the same as in rat hearts perfused with a normal concentration of Ca2+. The results suggest that the weak Gregg's phenomenon seen in guinea pig hearts can be attributed to factors other than myocardial edema and a lower left ventricular systolic pressure.

Myocardial adaptation to long-term action of substances associated with decreased intensity of cardiac function.

The effect of prolonged treatment of rats with 6-n-propyl-2-thiouracil (PTU), verapamil, or propranolol on cardiac pump function and the properties of myofibrils and mitochondria was studied. After 6-8 weeks of treatment, the heart rate and maximal cardiac output of the isolated heart of rats treated with verapamil or propranolol were higher than those in the control group. The PTU treatment was followed by lower heart rate and maximal work. Calcium sensitivity (pCa50 value) of skinned ventricular fibers was higher in all experimental groups compared to the control by 0.07-0.15 units. Myofibrillar Mg2+, Ca(2+)-ATPase activity measured in isolated Triton-skinned cardiomyocytes was considerably lower after PTU treatment than that in respective controls (0.128 +/- 0.013 vs 0.178 +/- 0.010 mumol Pi/min/mg protein). In contrast, long-term treatment with verapamil or propranolol was accompanied by increased activity to 0.223 +/- 0.018 and 0.254 +/- 0.015 mumol Pi/min/mg protein, respectively. Neither the basal mitochondrial respiration rate of saponin-skinned cardiac fibers nor its enhancement after addition of low ADP concentration or creatine was significantly altered in any experimental group. Also no difference between control and experimental groups was observed in the total activity of creatine kinase or relative percentage of its isoenzymes extracted from cardiac tissue. Thus the changes in cardiac pump function after prolonged treatment with agents decreasing cardiac function may be attributed to concomitant alterations of myofibrils while mitochondria remain relatively intact.

[Protective effect of 2,3-butanedione monooxime on ischemic myocardium of rats]. / Zashchitnoe deistvie 2,3-butandion monoksima na ishemicheskii miokardkrys.

Effects of 2,3-butanedione monoxime (BDM), an ATPase inhibitor, on ischemia-reperfusion myocardial injury were examined in isolated working rat hearts perfused in vitro. Following cardiac arrest induced by cardioplegic solution, global ischemia was produced for 30 min. In untreated hearts, reperfusion for 45 min resulted in an incomplete recovery of cardiac pump function. When BDM was added to the cardioplegic solution up to 20 mM, the recovery of cardiac function was significantly improved average by 19%. This BDM effect can, presumably, reduce ATP losses during ischemia and like that improve recovery of cardiac function during reperfusion.

[High functional activity of mitochondrial creatine kinase of the myocardium before ischemia is tied with the worst restoration of contractility after reperfusion]. / Vysokaia funktsional'naia aktivnost' mitochondrial'noi kreatinkinazy miokarda do ishemii sochetaetsia s khudshim vosstanovleniem sokratimosti posle reperfuzii.

Isolated Langendorff-perfused guinea pig hearts were arrested with a cardioplegic solution containing 10 mM phosphocreatine + 15 mM glutamate (PG group) or not containing them (control group). Total normothermic ischemia lasted 45 min followed by 30 min reperfusion. Mitochondrial respiration in the absence and presence of different concentrations of ADP and creatine was studied in biopsy samples after saponin treatment. The samples were taken before and after ischemia as well as after the reperfusion period. A slightly better relative recovery of developed pressure (RRDP) in PG group was associated with higher mitochondrial acceptor control ratio after reperfusion. When results in both groups were taken together, marked negative correlations between the preischemic mitochondrial indices (particularly, those related to creatine kinase activity) and RRDP were revealed. Relative changes in these indices after ischemia demonstrated tight positive correlations with RRDP. Thus, the hearts having higher functional activity of mitochondrial creatine kinase are more sensitive to ischemia, other conditions being equal.

Mitochondrial respiration in myocardial biopsy samples as a criterion of postischemic recovery of the cardiac contractility.

Isolated perfused guinea pig hearts were arrested by a high K+ cardioplegic solution containing (PG group) or lacking (control group) 10 mM phosphocreatine + 15 mM glutamate. Total normothermic ischemia lasted 45 min followed by 30 min reperfusion. Mitochondrial respiration in the absence and presence of different concentrations of ADP and creatine was studied in biopsy samples (6-8 mg) after saponin treatment. The samples were taken before and after ischemia, as well as after the reperfusion period. A slightly better relative recovery of developed pressure (RRDP) in PG group was associated with higher mitochondrial acceptor control ratio after reperfusion (5.74 +/- 0.32 vs. 4.54 +/- 0.21 in PG and control groups, resp., p less than 0.01). When the results obtained in both groups were treated together, tight correlations between the pre- or postischemic mitochondrial state and RRDP were revealed. Higher values of RRDP were found for the hearts with lower preischemic values of (low ADP + creatine)-stimulation of mitochondrial respiration (r = -0.57, p less than 0.01). Relative changes in this mitochondrial parameter during ischemic period were in a good correlation with the RRDP (r = 0.82, p less than 0.001). The data suggest that the study of the mitochondrial function in myocardial biopsy samples before ischemia and reperfusion could provide a useful information for the prognosis of cardiac function recovery.

[Coronary vessel tonus and cardiac resistance to ischemia in chronic adriamycin-induced myocardial damage]. / Tonus koronarnykh sosudov i rezistentnost' serdtsa k ishemii pri khronicheskom adriamitsinovom porazhenii miokarda.

The rats receiving a cumulative dose of adriamycin, 15-20 mg/kg exhibited delayed weight gain, ascites, and increased relative liver weight. The animals' isolated hearts perfused at a constant rate in the Krebs' solution in a retrograde fashion showed lowered perfusion pressure, indicating reduced coronary vascular tone. At the constant heart rate, the hearts from the adriamycin-treated animals consumed oxygen less at equally increased pressure. In total ischemia, higher cellular lactate and K+ yield occurred than in controls, the severity of acidosis being nearly similar. Prior to ischemia, the pressure produced by the hearts from adriamycin-treated animals was less but, following reperfusion, it more rapidly became normal than that in controls. The results suggest a compensatory increase in myocardial glycolysis during chronic administration of adriamycin.

[Differences in the reaction of rat and guinea pig hearts to ischemia and reperfusion]. / Razlichiia v reaktsii serdets krys i morskikh svinok na ishemiiu i reperfuziiu.

The response of rat and guinea-pig hearts to ischemia and reperfusion has been studied in identical conditions. Total 15-min ischemia of isolated rat hearts at 36 degrees C induced an almost 3-fold rise in isovolumic left ventricular diastolic pressure as well as a fall in the developed pressure and heart rate. Guinea-pig hearts, in the same conditions, exhibited a more steep fall in heart rate, with no rise in diastolic pressure. With constant heart rate produced by electrical stimulation at 4 Hz, the difference between two groups remained unchanged, while a more rapid fall in developed pressure in guinea-pig hearts coincided with a more profound fall in extracellular pH and almost a 2-fold rise in extracellular K+ activity. Rapid elimination of K+ and H+ at the early stages of reperfusion was followed by fibrillation in the majority of guinea-pig hearts, while no fibrillation was observed in rat hearts.

[Continuous observation of catecholamine release into the blood of the coronary sinus in experimental myocardial infarct complicated by ventricular fibrillation]. / Nepreryvnoe nabliudenie za osvobozhdeniem katekholaminov v krov' koronarnogo sinusa pri oslozhnenii éksperimental'nogo infarkta miokarda fibrilliatsiei zheludochkov.

It was established that the content of adrenalin and noradrenalin in the coronary sinus blood increases after occlusion of the coronary artery. In experiments terminating in ventricular fibrillation the concentration of catecholamines was found to be increased more markedly. A temporary correlation was established between an increase in the catecholamine level in the blood of the coronary sinus and the development of ventricular fibrillation. It is assumed that catecholamines are the triggering mechanism in the development of ventricular fibrillation.