[Biological activity of chalone-like proteoglycans during ontogeny]

A chalone-like proteoglycan was isolated from the liver of 2 and 24 month old cattle and Wistar rats which inhibited mitoses in the liver cells of C57BL mice starting from 5-6 days after birth. The effect of this proteoglycan was tissue but not species specific. We failed to isolate this proteoglycan from the liver of newborn rats, thus suggesting that either this substance is not produced by the cells of newborn animals or is produced in insignificant quantities. The proteoglycan isolated from the liver of the old rats, unlike that from the liver of 2 month old rats, was not effective in the same doses and this suggests changes in its chemical composition.