Inhibition of the in Vitro Synthesis of Pituitary Prolactin and Growth Hormone by Mouse Pituitary Isografts 1

Summary

Pituitary glands from mice bearing pituitary isografts in the renal capsule for 6-74 weeks were incubated with ¹⁴C- labeled amino acids, and the incorporation into prolactin and growth hormone was determined. Mice with isografts for 23 weeks synthesized 60% less prolactin and growth hormone than did normal intact mice. Implantation of isografts for periods up to 74 weeks further decreased the ability of the pituitary gland to synthesize the prolactin hormone; however, at 74 weeks, the extent of this inhibition in growth hormone synthesis was some-what decreased. It is proposed that the decrease in prolactin and growth hormone synthesis is mediated by hormone(s) secreted by the tumor acting at the hypothalamo-pituitary level through an autofeedback process.

The author thanks Prof. O. Muhlbock and Drs. L. M. Boot and H. W. Kwa for providing the laboratory facilities and fruitful discussions during his visit to the Netherlands Cancer Institute.