Pituitary autografts placed under the renal capsule of adult female rats in estrus were found to produce luteotrophin. Indirect evidence indicates that autografts in male and female rats which were operated on at puberty probably produce this hormone also. Studies on both the adult and
pubertal
animals indicate that pituitary autografts produce the other anterior lobe hormones either at a very low level or not at all.
The predominant chromophilic cell type in grafts known to be producing luteotrophin is an elongated acidophile staining selectively with orange G when the
azan
stain is used. Two types of acidophiles were found in the intact rat pituitary, one staining with azocarmine and the other with orange G. The latter has the same morphology as the predominant cell type in active autografts and is considered to be the source of luteotrophin in the rat.
This study was supported by research grant R. G. 4723 from the U.S. Public Health Service.