An investigation of respiration of rat heart muscle slices was carried out using the manometric technique. The experimental method was described in Part I of this article. In this report, the respiration in the presence of lactic acid and pyruvic acid as substrate was studied comparing with that of glucose.1) The presence of lactic acid increased respiration of heart muscle slices. When gas was pure oxygen, Qo₂ in the first hour was 18.7 or 17.2, when lactate concentration was 0.01 M or 0.02 M accordingly. It was twice as high as the endogenous respiration value. When gas was air, it decreased to about 40 per cent, namely 7.6 and 7.4 of Qo₂, (Fig 1, 2. Table 1, 2, 3, 4.)2) In the presence of pyruvic acid, oxygen consumption was greater than in lactic acid medium. When. pure oxygen was used, Qo₂ was 24.9 in 0.01 M, and 26.5 in 0.02 M. When air was used, 9.1 and 7.9 respectively. (Fig 3, 4. Table 5, 6, 7, 8) 3) In both lactate and pyruvate medium, respiration rate deceased gradually hour by hour, so Qo₂ at the fourth hour was about 50 per cent of its initial value.4) In both substrates medium, . oxygen consumption of heart muscle slices was independent of its concentration (at least between 0.01 M and 0.02 M).5) Comparing these results with that of experiments (in glucose medium) reported in the Part I of this article, it could be considered as follows; glucose is a steady and constant fuel of the heart muscle, while lactate and pyruvate are fuels for the emergency metabolic demand, especially when the concentration of these substances in blood is elevated, because they are oxidized easily and rapidly in contrast with glucose.6) When gas was air, Qo₂ was about as one third as in pure oxygen, disregarding the kind of substrate (glucose, lactate, or pyruvate). So it was suggested that hypoxemia in such degree as 20 per cent O₂ at least, never damages lacticodehydrogenase nor other enzyme which mediates the chemical transmit from carbohydrate to Co₂.

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In order to study the disturbance of carbohydrate metabolism in the development of hypertension, statistical correlation between hypertension and diabetes was studied in total of 10, 798 patients admitted to our clinic during the past 20 years (1933-1952).Patients with hypertension (P₁, above 150 ; P₅, above 90 mmHg) were 734 cases (6.8 %), diabetes, 173 cases (1.6 %), and patients with both combined, 52 cases (0.5 %). The last type of involvement occurred in 7.1 % of patients with hypertension, and in 30.0 % of diabetes. Of these 52 cases, diabetes preceded hypertension in its onset in 23 cases (44 %), hypertension preceded diabetes in 8 cases (15 %), unknown in 20 cases (39 %), and Cushing's disease occurred in one case (2 %). Namely, hypertension occurred in diabetes 4.7 times as often as in nondiabetics. Diabetes occurred in hypertensive patients 5.9 times as often as in nonhypertensive patients. Though the material available for this statistic survey has been limited to hospitalized patients, this result is generally consistent with the reports from abroad and it is obvious that diabetes and hypertension are correlated with each other, suggesting that the disturbance of ATP-ATPase system, or allied metabolic disturbance may play an important part in the development of hypertension.

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The authors investigated influence of salt upon congestive heart failure and got following results and conclusion.(1) When 1000 cc of 1 % salt solution was given orally, it was less excreted in cases of congestive heart failure than in normal subjects.(2) This, the authors think, does not mean any defficiency of renal function but rather mean that salt excretion stands under the control of various other bodily functions.(3) This idea comes from following experimental results : (a) Salt was fairly well excreted even in congestive heart failure when large quantity of it was orally given.(b) Excretion of water was better than that of salt solution when they were given orally in cases of congestive heart failure.If renal function in general is damaged, it is in contradiction with the fact stated in (b). If renal function for salt excretion is exclusively damaged, it is in contradiction with the fact stated in (a).

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The authors at first made formula from which assumed normal cardiac size could be calculated in reference to body-weight and length. Actual cardiac size/assumed normal cardiac size was called dilatation-gradient : actual cardiac size was measured by planimeter in its shadow in the direct postero-anterior projection of X-ray. Relatiohship between circulation time and dilatation-gradient was investigated in cases of congestive heart failure and non-congestive cardiac disease, and linear relationship was demonstrated between them. This does not mean that prolongation of real circulation time (decrease of blood velocity) is due to dilatation of heart. Because circulation-time, clinically used, shows not only the blood velocity but also the degree how much the drug injected is diluted by blood.

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