Abstract
Summary
Rats bearing a transplantable adrenal cortical carcinoma showed the following features: elevated levels of an erythropoietic factor in the serum 2–4 weeks after tumor transplantation; no increase in erythropoietic factor in the serum 2 months after transplantation; significant levels of an erythropoietic factor in saline extracts made of both the young and the old tumor tissue; and no significant reduction of erythropoietic factor in the serum or tumor 48 hr after nephrectomy of the tumor bearing rats. This evidence indicates that the site of production of the erythropoietic factor is the tumor itself. Several features of the active tumor extracts. primarily its inactivation by neuraminidase, supports the contention that the eryth-ropoietically active material in these rats is erythropoietin.
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