Mitogenic Stimulation

The mitogenic effect of a new growth factor that we recently isolated from the acellular ascitic fluid of the Ehrlich ascites carcinoma grown in vivo was examined. We have called this fac tor EACF (Ehrlich ascites c a r c i n o m a f a c t o r ) . EACF caused in i t ia t ion of DNA s y n t h e s i s in the l iver 9 submandibular gland, exo rb i t a l lacrimal gland and epithelium of the tongue of adult mice after i.p. injection at a protein concentration of 3 pg per 25 g of body weight. For all tissues examined, except the tongue, EACF init iated DNA synthesis at about 48 to 60 h after injection, with the maximum e f fec t at approx. 85 h, and the stimulatory effect lasting approx. 60 h. The init iat ion of DNA synthesis in l iver, which is normally characterized by only an occasional cell passing through the S phas% by EACF is of particular interest. The init iat ion of DNA synthesis in the l iver was not prevented by hypophysectomy. Evidence also indicates that a similar heat-labile growth promoting factor(s) is present in calf serum.