Characterization and partial purification of a substance in the pineal gland which inhibits cell multiplication in vitro.

A substance which inhibits the in vitro multiplication of 3 cell strains, 37 RC, KB and NCTC clone 929, was characterized in the sheep pineal gland and partially purified using three successive chromatography techniques, respectively on Sephadex G-25, CM-cellulose and Biogel P 60 columns. The sheep cerebral cortex and liver also contain, but at much lower concentration than in the pineal, substance(s) that behave in different tests like the factor isolated from the pineal. The nature of the antimitotic substance from the pineal is as yet unknown. It is not destroyed by treatment with proteolytic enzymes, nor by boiling with 6 M HC1. It was established that it is different from the known antiblastic drugs such as Daunomycin and Methotrexate and from some active substances known to be present in the pineal, such as melatonin, secotonin and norepinephrine, which, in the same conditions, did not show any antimitotic activity. It was shown that when the concentration of the pineal factor in the culture medium was high enough (10 mug/ml), the inhibition of the KB cells multiplication was complete and irreversible. Microscopic examination of the treated cells showed that the morphological alteration was rapid (3--6 h) and deep, with shrinkage of both cytoplasm and nucleus, while with antiblastic drugs, morphological alteration proceeded slower (1--3 days) and appeared less pronounced.