Abstract
Summary
Administration of 5-fluorouracil (5-FU) caused enlargement of the adrenal glands in Wistar and A × C rats. Results of simultaneous administration of cortisone and/or ACTH suggest that this enlargement is due to stimulation of secretion of ACTH rather than to enhancement of its activity. The enlarged adrenals of animals bearing the Walker tumor, Murphy-Sturm lymphosarcoma or Morris hepatoma 3924C did not enlarge further under treatment with 5-FU. They were reduced in size by administration of cortisone, more so in the case of the Walker tumor. The suppressive effect of cortisone was not overcome by simultaneous administration of 5-FU in rats bearing the lymphosarcoma or hepatoma but was in those with the Walker tumor. The ACTH-secreting mechanism in the latter is apparently more sensitive both to suppression by cortisone and to stimulation by 5-FU. The Walker tumor was sensitive to the tumoristatic action of cortisone and relatively resistant to that of 5-FU, whereas the converse was the case for the lymphosarcoma and hepatoma. These 3 tumors therefore exhibit a reciprocal relationship between sensitivity to cortisone and to 5-FU similar to that reported for corticosteroid-sensitive and resistant strains of mouse lymphoma P-1798.
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