Changes in myocardial potassium balance without variation of the interstroke interval

Cingolani, H.E.; E, Blesa; Gonzalez, NC; Lew, Michael S.; Jc, Marsiglia

doi:10.1152/ajplegacy.1966.210.1.181

Cited by 6 publications

(4 citation statements)

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“…Several theoretical possibilities besides a direct action of H + or CO 2 upon the contractile machinery can be contemplated. The first hypothesis devolves from the fact that interventions that increase myocardial contractility are frequently associated with changes in myocardial potassium balance (25,26), a release of potassium from the cell occurring during an increase in performance. This hypothesis is related to the findings of Brown and Goot (27), who demonstrated that a decrease of the ratio of intracellular to extracellular H + activity promotes a net loss of potassium from the skeletal muscle cell; on the other hand, the demonstration that hypercapnia is associated with an uptake of potassium by the myocardium gives support to this theory (28).…”

Section: Summary Of the Changes In Developed Tension And Maximal Dt/dmentioning

confidence: 99%

Contractility in Isolated Mammalian Heart Muscle after Acid-Base Changes

Cingolani

Mattiazzi

Blesa

et al. 1970

Circulation Research

111

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In-vitro experiments performed in cat papillary muscles and strips of rat right ventricle suggest that the changes in myocardial contractility that follow acid-base disturbances are not a function of extracellular pH. Simultaneous changes in Pco 2 and NaHCO 8 concentration, with extracellular pH constant, decreased developed tension and maximal rate of rise of the tension (dT/dt) without significant changes in the time to peak tension when the muscle was exposed to the solution with higher Pco 2 and NaHCO 8 concentration. At an extracellular pH of 7.40, developed tension decreased 0.51 ± 0.13 g/mm 2 (P<0.02) and dT/dt decreased 1.29 ± 0.50 g/sec (P < 0.05) with no significant change in time to peak tension (0.038 ± 0.022 sec). Changes in pH produced by increasing Pco 2 at constant NaHCO 3 concentration were followed by a significant decrease in contractility. A change of Pco 2 from 20 to 90 Tnm Hg that produced a change in extracellular pH from 7.60 to 7.00 was accompanied by a decrease in developed tension of 0.67 ± 0.14 g/mm 2 (P<0.01), in dT/dt of 2.63±0.54 g/sec (P<0.01) with no changes in time to peak tension (0.0017 ± 0.10 seconds). We were unable to show significant variations in contractility when extracellular pH was changed at a constant Pco 2 of approximately 21 mm Hg (NaHCO 8 7.5, 15, and 30 DIM) or at a Pco 2 of approximately 95 mm Hg (NaHCO 3 15, 30, 60, 80 and 120 HIM). Only when extracellular pH reached a value as high as 8.0 (Pco 2 21 mm Hg, NaHCO 3 80 HIM) a small but significant increase in contractility was evidenced. Either Pcoj or intracellular pH could be the major determinants of the changes in myocardial contractility that follow acid-base alterations. gest that contractility is a function of external pH and independent of the way in which a change in pH took place. These authors concluded that the observed changes were most closely associated with external pH. Changes in P002 alone had no significant effect. On the other hand, Lorkovic (3), using an in-vitro preparation of isolated frog ventricular muscle, concluded that both intra-and extracellular pH play a role in the observed changes in contractility. It is difficult to ascertain whether the changes in cardiac performance observed in isolated blood-perfused hearts, heart-lung, or more intact preparations are due to variation in blood pH, Pco 2 , or both (3-10).Recent experiments in our laboratory on heart-lung preparations or perfused dog hearts have demonstrated that heart performance is affected by changes in Pco 2 but not by changes in pH when Pco 2 is kept constant (11).Considering the discrepancies between our results and those obtained with in-vitro preparations by other authors, experiments were undertaken on cat papillary muscles and strips of rat right ventricle to supply information about the effect of Pco 2 , pH, and NaHCO 3 concentration on mammalian ventricular contractility. Evidence will be presented that in changing ventricular contractility during extracellular pH alterations, the way in which a change in ex...

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Section: Summary Of the Changes In Developed Tension And Maximal Dt/dmentioning

confidence: 99%

Contractility in Isolated Mammalian Heart Muscle after Acid-Base Changes

Cingolani

Mattiazzi

Blesa

et al. 1970

Circulation Research

111

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“…Table 1 shows the potassium balance data from all the experiments. Prior to balloon inflation there was an average up-772 GILMORE, GERLINGS 5 6…”

Section: Resultsmentioning

confidence: 99%

“…• When left ventricular outflow resistance is increased myocardial contractility increases (1)(2)(3)(4), and potassium is lost from the heart (2,3,5). It has been suggested that this loss of potassium contributes to the change in contractility and is related to the associated increase in developed tension (2,3,5).…”

Section: Additional Abstract Myocardial Kmentioning

confidence: 99%

“…It has been suggested that this loss of potassium contributes to the change in contractility and is related to the associated increase in developed tension (2,3,5). When the preload of cardiac muscle is increased over a wide range, the developed tension increases; however, it is generally assumed that under these circumstances the contractility of the heart is not altered.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Developed Tension on Myocardial Potassium Balance in the Dog Heart

Gilmore

Gerlings

1968

Circulation Research

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Experiments were carried out to determine the effect of changing preload on myocardial potassium balance. A blood-perfused dog heart was employed. Changes in the pressure recorded from a balloon in the left ventricle were assumed to reflect directional changes in myocardial wall tension. Developed tension was altered by changing the volume of the balloon. Net potassium balance was calculated as the product of the coronary A-V plasma potassium difference and coronary plasma flow. When the ventricle was developing little tension, it usually gained potassium. When diastolic volume and thus developed tension was increased, a net loss of myocardial potassium occurred. In some experiments the hemodynamic response of the ventricle to the increase in diastolic volume suggested that the contractility of the heart was increasing while the heart was losing potassium.ADDITIONAL KEY WORDS myocardial K + balance myocardial contractility ventricular tension myocardial tension and potassium balance• When left ventricular outflow resistance is increased myocardial contractility increases (1-4), and potassium is lost from the heart (2, 3, 5). It has been suggested that this loss of potassium contributes to the change in contractility and is related to the associated increase in developed tension (2,3,5). When the preload of cardiac muscle is increased over a wide range, the developed tension increases; however, it is generally assumed that under these circumstances the contractility of the heart is not altered. If the loss of potassium when aortic resistance is increased is the result of the augmented developed tension, a loss would also be expected when developed tension is increased by preload. Further, if such a loss occurred and if the increase in contractility when aortic resistance is raised is related to a loss of myocardial

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