Mammotropic and somatotropic hormones in sera of normal rats and in rats bearing primary and grafted pituitary tumors

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Abstract
Parallel determinations were made of the concentration of MtH and StH in the sera of rats with spontaneous, estrogen‐induced and grafted pituitary tumors and, for a base, in sera of normal rats of both sexes, in various physiologic states, following oophorectomy and treatment with gonadal hormones.The characteristic sharp rise of MtH during proestrus was confirmed. This was not accompanied by a rise in StH.Following oophorectomy the levels of both hormones dropped. After estrogen treatment of normal rats, both hormones rose gradually, reaching very high levels with development of pituitary tumors. Similar increases were found with spontaneous mammotropic tumors (MtH) in rats of both sexes.Seven MtT's, originating in six different strains, were studied in the course of successive transplantations. All exhibited mammary gland stimulation, with very high MtH and StH levels, depending on the tumor size and tumor strain. In general, hormone secretion decreased in the course of successive transplantations.One variant of the originally typical MtT.W5, MtT.W5/H, markedly lost the ability to produce MtH while maintaining the ability to produce StH, as indicated by both radioimmunoassays and biological changes in the tumor hosts. The oldest transplantable tumor of this series (MtT.F4), secreted large quantities of AtH and StH without biological evidence of somatotropic effects. The StH effect became “unmasked” by adrenalectomy. Biological evidence of AtH secretion by the other MtH strains was inconstant and variable. It was often present in the first transplant generation but vanished in the course of successive transplantations with the exception of the F4 strain.The MtH values in normal as well as MtT‐bearing hosts were higher in female than in male rats. There was relatively more StH in males than in females.