Mitotic variations in the lens epithelium of the frog IV. Studies with isolated anuran pituitary factors.

Proteins corresponding to growth hormone and prolactin have been electrophoretically separated from the pituitary gland of the frog (Rana pipiens berlandieri and Rana catesbeiana). These substances can independently stimulate mitosis in the lenses of animals where it had previously been inhibited by means of hypophysectomy. DNA synthesis is greatly augmented six days after the start of hormone administration to intact animals. Nine days are required before this occurs in hypophysectomized ones. No other anterior pituitary hormone has been found to achieve the effect described. Initial attempts at amino acid analysis, though incomplete, indicate that the two frog hormones are different from each other as well as from their bovine counterparts. Pituitary factors do not affect mitotic activity in either corneal epi or endothelium of the frog.