IN VITRO INTERCONVERSION OF 16-C14-ESTRONE AND 16-C14-ESTRADIOL-17β BY ERYTHROCYTES FROM NORMAL SUBJECTS AND FROM SUBJECTS WITH A DEFICIENCY OF RED CELL GLUCOSE-6-PHOSPHATE DEHYDROGENASE ACTIVITY*

Werthessen and his collaborators (2-4) reported that incubation of estrone in blood produced the destruction of the 17-ketone function of the steroid, accompanied by a loss of biological activity. On the other hand, Bischoff and associates (5, 6) in- cubated the red blood cells of rabbit or man with estrone and observed a marked increase of the biological activity of the added steroid. The dis- crepancy in the two sets of data was ascribed at the time to differences either in assay techniques or in experimental conditions. A similar increase in biological activity was reported by Repke and Markwardt (7), who used red cells of the guinea pig, rabbit, and man. It now appears that spe- cies differences were the cause of this discrepancy. In most of these experiments, Werthessen and co-workers (3, 4) used bovine blood, and Axelrod and Werthessen (8) have found that in this spe- cies estrone is converted to the extent of 88 per cent into estradiol-17a. The investigations of Bischoff and associates (5, 6) were carried out with rabbit and human red cells, and these au- thors (9) have shown that the main reaction product resulting from estrone incubation in their system was estradiol; the latter report, however, failed to mention whether the steroid detected was the a-or 8-isomer, but there are reasons to be- lieve that reaction product was estradiol-17/3. This isomer is biologically more active than estrone or estradiol-17a; hence the difference in the re- sults reported by Werthessen and co-workers (3, 4) and Bischoff and associates (5, 6). In a