Early cyclical changes in polyamine synthesis during sea-urchin development.

The polyamines, putrescine, spermidine, and spermine, undergo dramatic cyclical variation in both synthesis and accumulation during the early cleavage stages of sea-urchin development. Ornithine decarboxylase activity (putrescine synthesis) in developing Strongylocentrotus purpuratus exhibits maxima at •£• and 2 h after fertilization; increases in ornithine decarboxylase activity appear to correspond to the first and second S phases. Putrescine-stimulated S-adenosyl-L-methionine decarboxylase (spermidine synthesis) and spermidine-stimulated S-adenosyl-L-methionine decarboxylase (spermine synthesis) activities reflect rises during prophase-metaphase of the first and second divisions in two species of sea urchins. Cyclical changes in the concentrations of these three amines were evident also. In general, there were drops in the levels of the amines prior to cleavage. These rapid declines in polyamine concentrations may reflect (.1) selective degradation or (2) selective secretion.