Effect of palytoxin and serotonin on murine tumor cells

In vitro and in vivo effects of two fractions of a crude extract from the marine invertebrate Palythoa were investigated in Novikoff hepatoma and Ehrlich ascites tumor cells. These fractions, previously identified as serotonin and a partially purified toxin, inhibited thymidine incorporation into acid-precipitable material by tumor cells. Results from respiration studies indicated that the inhibitory effect was not toxic. The data suggested that: a) The partially purified toxin exerted its inhibitory effect at the membrane level; b) this inhibitory effect might have been accomplished through the Na+K+ transport mechanism, this conclusion being supported by data on the uptake of labeled amino acids by Ehrlich ascites tumor cells; and c) in an unconfirmed experiment, the partially purified toxin increased the survival time of 50% of 6 palytoxin-treated mice at least three times as long as 6 untreated control mice. All 12 mice had received 1 X 10(6) viable Ehrlich ascites tumor cells.