Format

Send to

Choose Destination
Acta Physiol Scand. 1993 Dec;149(4):427-33.

Myocardial lactate release during prolonged exercise under hypoxaemia.

Author information

1
Karolinska Institute, Department of Clinical Physiology, Huddinge Hospital, Stockholm, Sweden.

Abstract

The possible appearance of myocardial lactate production during exercise under hypoxaemia, simulating an altitude of about 4500 metres above sea-level (masl) was investigated. Twelve healthy men were studied, after coronary sinus catheterization, during prolonged exercise breathing 12% O2 compared with men breathing air. Coronary sinus blood flow was measured by thermodilution. Exercise duration under each breathing condition was 30 min and the order normoxaemia/hypoxaemia was varied between subjects so as to compensate for any influence of a preceding exercise period on a subsequent one. Work load was adjusted so as to produce a heart rate (HR) of 130-140 beats min-1 during both hypoxaemia and normoxaemia. [14C]lactate was infused at a constant rate i.v. throughout the study to detect a possible myocardial lactate release simultaneously with a net uptake. Myocardial O2 uptake did not differ significantly between hypoxaemia and normoxaemia. The compensation for reduced blood oxygen content was achieved entirely by a greater coronary blood flow. Yet, the arterial-coronary sinus (a-cs) lactate difference was lower during hypoxaemia than normoxaemia and isotope data indicated that this was caused by a myocardial lactate release of approximately 90 mumol min-1 which was at hand during hypoxaemia but not normoxaemia, whether hypoxaemic exercise preceded or succeeded normoxaemic exercise. In conclusion, A 27% reduction in arterial oxygen saturation is almost compensated for by an increased coronary blood flow. However, during hypoxaemic exercise cardiac energy demand is to a smaller part, about 1%, covered by anaerobic metabolism.

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Wiley
Loading ...
Support Center