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In a previous study on acute asphyxia in unanesthetized fetal sheep near term we showed that reduced oxygen delivery to peripheral organs reduces total oxygen consumption, suggesting that oxygen itself may be a determinant of oxygen consumption (Jensen, Hohmann & Künzel, 1987). To test this hypothesis we developed an in vitro perfusion model, which enabled us to measure the oxygen consumption of fetal skeletal muscle cells in monolayer culture in a control period (at approximately 145 mmHg) and during various degrees of hypoxia (6-140 mmHg). In 57 experiments on 57 cultures the mean oxygen consumption at a mean 'entry PO2' of 145.3 +/- 10.4 mmHg was 10.3 +/- 9.3 (SD).10(-6) microliters O2 per h per skeletal muscle cell. These measurements were made after an average of 4.2 +/- 2.3 transfers of the cells and at a cell density of 2.0 +/- 1.2.10(5) cells per cm2. In 54 of these experiments hypoxia was induced. There was a close positive correlation between the PO2 of the perfusate entering the Petridish ('entry PO2') and the change of the oxygen consumption of the cells (y = 5.17 - 0.54x + 0.03x2 - 0.00016x3, r = 0.97, p less than 0.0001). When oxygen tension fell, there was a concomitant fall in cellular oxygen consumption. We conclude that oxygen is a determinant of cellular oxygen consumption. Thus, hypoxia may reduce oxygen consumption of skeletal muscle cells, and oxygen may be preserved to maintain oxidative metabolism in central fetal organs.(ABSTRACT TRUNCATED AT 250 WORDS)