The importance of glucose in the oxidative metabolism of the testis of the conscious ram and the role of the pentose cycle.

1. [U-(14)C]Glucose was infused into one or both testicular arteries of ten conscious rams and the specific activity of the glucose taken up by the testis was compared with the specific activity of the carbon dioxide produced by the testis. 2. Equilibration had occurred after infusion for 3hr. when a mean of 68% of the carbon dioxide was being derived by the testis from blood glucose and 86% of the glucose taken up by the testis was being oxidized to carbon dioxide. After 5hr. infusion, these values were 71% and 83% respectively. 3. In four other conscious rams, [1-(14)C]glucose was infused into one testicular artery and [6-(14)C] glucose into the other and the ;specific yields' of carbon dioxide calculated for the two forms of glucose. 4. From these values, it was calculated that a mean of 9.3% of the glucose taken up by the testis was metabolized via the pentose cycle.