ABSTRACT
Polyamines have been shown to be essential for nucleic acid synthesis and proliferation in a wide variety of cell systems. Ornithine decarboxylase (ODC), the rate-limiting enzyme in polyamine synthesis, generally attains a transient peak in activity shortly before the initiation of DNA synthesis. In Asterias vulgaris, ODC activity increases greatly during the proliferative phase of spermatogenesis. Intact testes near the beginning of the proliferative phase were supplied with exogenous polyamines and subsequently showed a significant increase in incorporation of H-thymidine into DNA. However, prior intracoelomic injection of polyamines showed no sustained effect on thymidine incorporation; after 24 hours incubation in polyamine-free medium, the rate of thymidine incorporation was statistically indistinguishable from that in control specimens. These results suggest a direct role for polyamines in the regulation of spermatogenic proliferation in A. vulgaris.
