THE METABOLISM OF THE ISOLATED MAMMALIAN HEART UNDER PARTIAL ANOXIA

¹ The Department of Physiology, Pharmacology, and Biochemistry, University College, London

1. In gradually increasing anaerobiosis the heart continues to use glucose and lactate. Failure occurs when the oxygen tension has fallen to between 15 and 30 mm. Hg. The onset of failure is sudden.

2. There is evidence of a production of lactic acid in the terminal stages of asphyxia.

3. The survival time of the heart is prolonged by increased glucose concentration in the blood. The presence of lactate does not appear materially to affect the survival time.

4. Glycogen depletion is prevented by moderate concentrations of glucose and lactate. High lactate alone prevents the depletion of glycogen. But with low lactate and normal glucose some glycogen breakdown can occur.

5. The heart is able to immobilise I.A.A., since the addition of I.A.A. to the circulating blood in the heart-oxygenator preparation does not inhibit glycolysis.

6. Glycolysis is inhibited by the addition of I.A.A. to blood which is not afterwards circulated through the heart.

7. Concentrations of I.A.A. up to 1 : 10,000 have no apparent effect on the usage of glucose and lactate by the heart in aerobic conditions.

8. The time of survival in anaerobiosis is shortened by the presence of I.A.A. The presence of lactate appears to prolong the survival time, while the presence of glucose tends to shorten this time. But glucose prevents the depletion of glycogen under these conditions.

9. The heart, when poisoned with I.A.A. and asphyxiated, continues to utilise glucose and lactic acid, and glycogen if the blood glucose and lactate is low.

The authors wish to acknowledge their indebtedness to Professor C. Lovatt Evans for the excellent facilities, helpful criticism, and advice throughout the course of this work.

The costs of this investigation were in part defrayed out of a grant from the Thomas Smythe Hughes and Beaverbrook Funds by the University of London to R.A.G., and of a grant from the Government Grants Committee of the Royal Society to J.Y.B.