1. Testosterone, administered in vivo, was observed to have no effect on glutamic-aspartic transaminase, glutamic-alanine transaminase, DOPA decarboxylase, and cysteine desulfhydrase activity of the tumor (755) and normal mouse tissues studied. Similar results were obtained for glutamic-aspartic and glutamic-alanine transaminase activity in liver and skeletal muscle utilizing slice technics.

  2. The in vivo administration of testosterone and deoxypyridoxine in combination increased the sensitivity of glutamic-aspartic transaminase, glutamic-alanine transaminase, and DOPA decarboxylase to antagonism by deoxypyridoxine, the point of maximal inhibition being reached at an earlier time than when the antagonist was administered alone. Deoxypyridoxine, alone or in combination with testosterone, had no effect on cysteine desulfhydrase activity.

  3. The administration of pyridoxine ½ hour prior to the administration of deoxypyridoxine was observed to protect glutamic-aspartic transaminase from deoxypyridoxine inhibition regardless of whether the antagonist was given alone or in combination with the testosterone.

*

This work was supported by a grant-in-aid from the Damon Runyon Memorial Fund, the Mary Madison McGuire Memorial Fund and an anonymous cancer gift. A preliminary report appeared in Fed. Proc., 12:412, 1953.

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