Changes in hormone sensitivity of pituitary mammotropes during progression from normal to autonomous.

The autonomous mammotropie tumors (3I tT) studied have retained responsiveness to estrogen. Optimal growth of such tumors occurs at doses one-tenth tha t necessary to induce tumorous proliferation of mammotropie cells (Sit) in p i tu i ta ry glands in situ or in grafts or normal t)i tuitary tissue beneath the kidney capsule. The similari ty in sensitivity between normal 3 I t in situ and M:t in subeapsular grafts of normal p i tu i tary tissue indicates tha t immediate circulatory connection with the hypothalaInus does not play a dominant role in the effects of estrogen on the 3ft . The estrogen sensitivity of grafts of dependent 5~[tT is similar to tha t of normal X[t or intermediate between autonomous and normal Mt . These results suggest tha t gain in estrogen sensitivity may be an adapt ive phenomenon acquired gradually and is not an exclusive characteristic of autonomous cells. Additional results indicate tha t the subcapsular site is superior to both intramusenlar and subcutaneous graft sites for such studies.