CONTRIBUTION OF THE PENTOSE-PHOSPHATE SHUNT TO THE FORMATION OF CO2 IN SWIMBLADDER TISSUE OF THE EEL

The contribution of the pentose phosphate shunt to glucose metabolism in the swimbladder tissue of the American eel Anguilla rostrata has be en evaluated by comparing the rate of (CO2)-C-14 and [C-14]lactate pro duction from [1-C-14]glucose and [6-C-14]glucose. In blood-perfused sw imbladder preparations, 0.18+/-0.07 nmol min(-1) of [6-C-14]glucose an d 3.19+/-0.57 nmol min(-1) of [1-C-14]glucose were converted to CO2. T he rate of [C-14]glucose conversion to [C-14]lactate was about the sam e in preparations perfused with [6-C-14]glucose and with [1-C-14]gluco se. This may indicate that the C-5 skeleton formed in the pentose phos phate shunt is not returned to glycolysis and converted to lactate. Al though gas deposition was usually not measurable in these blood-perfus ed swimbladder preparations, (CO2)-C-14 was detected in the eel swimbl adder gas of preparations perfused with [1-C-14]glucose, but not in pr eparations perfused with [6-C-14]glucose. The results confirm the hypo thesis that, in the eel swimbladder epithelium, some of the glucose ta ken up from the blood is metabolized in the pentose phosphate shunt. T his results in the formation of CO2, which is released into the swimbl adder as well as into the bloodstream.