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Immunoreactive ß-Endorphin in the Rat Mammotropic Transplantable Tumor (MtT-F4)¹

Clinical Research Institute of Montreal, Montreal H2W 1R7,^,3 Canada

Raised levels of what appeared to be ß-lipotropin (ß-LPH), ß-melanotropic hormone, and ß-endorphin were detected by radioimmunoassay in the plasma of rats bearing the mammotropic transplantable pituitary tumor MtT-F4. The immunoreactivity to anti-ß-endorphin in the assay was displayed by a substance with the molecular weight of ß-LPH, as determined by gel filtration. Isolated cells of MtT-F4 tumor incubated in vitro released immunoreactive ß-LPH and ß-endorphin, with the expected molecular weights, into the incubation medium. These results suggest that the pituitary transplantable rat tumor MtT-F4 secretes peptides structurally related to ß-LPH.

¹ This work was supported by the National Cancer Institute of Canada.

² To whom requests for reprints should be addressed.

³ Affiliated with the "Université de Montréal" and the Hôtel-Dieu Hospital of Montreal.

Received 10/14/77. Accepted 3/ 1/78.