Apoptosis is regulated by polyamines in the cell cycle of Chinese hamster ovary cells

ABSTRACT

This paper deals with the relationship between the polyamine metabolism and apoptosis in the different phases of the cell cycle in a Chinese hamster ovary (CHO) cell line. Synchronously growing cells were obtained by the addition of 1.2 mM hydroxyurea and the progression through the cell cycle was monitored by determining the incorporation of 3H-thymidine in the DNA. Ornithine decarboxylase (ODC) activity showed a peak in S phase, while intracellular putrescine and spermine contents increased constantly, reaching to a maximum level at G2 phase; spermidine content doubled during G2 and increased four times during M, compared to G1. The increment in the endogenous polyamine content was associated to a diminished uptake from the medium. The apoptotic index was higher in G2 phase, coinciding with the maximum level observed in putrescine content. The results support the idea that intracellular putrescine level is closely related to apoptosis