Inhibition of cells in culture by polyamines does not depend on the presence of ruminant serum.

Using T-lymphocyte (T-LC) and granulocyte colony (GC) assays with truly proliferating cells, the inhibitory dose-response relationships of spermine and spermidine in the presence of selected sera have been examined. In contrast to previous studies which used [3H]thymidine uptake as an index of proliferation, in vitro inhibition by polyamines was shown to require neither foetal calf serum (FCS) nor the addition of any exogenous polyamine oxidase. Cells grown in the absence of FCS were between 5-50% as sensitive to polyamines as in its presence. By using specific inhibitors of polyamine oxidase, it was shown that polyamine-elicited mitotic inhibition in the absence of FCS was still dependent on a polyamine oxidase, and evidence is presented to show that the source of the enzyme is the cells themselves.