Antagonistic effect of polyamines on ABA-induced suppression of mitosis in Allium cepa L.

Effect of abscisic acid (ABA) and polyamines (PAs) [putrescine (Put), spermidine (Spd) and spermine (Spm)] on mitosis in root tips of A. cepa was studied. Treatment with ABA (0.1 to 100 microM) for 24 hr suppressed the mitosis, measured as mitotic index (MI), in a concentration-dependent manner with approx. 50% suppression at 10 microM of ABA. Treatment with different PAs (1 to 100 microM) had differential mitosis suppression effect. Spm was most inhibitory followed by Spd and Put, respectively. The higher concentrations of PAs (1 mM Put; 0.1 and 1 mM Spd or Spm) caused cell distortion. Remarkably, a 24 hr pretreatment of root tips with PAs prior to ABA (100 microM) treatment resulted in a general concentration-dependent reversal of ABA-induced suppression of MI. Catalase (CAT) activity in the root tips, an indicator of redox metabolism, increased due to ABA treatment in a concentration-dependent manner, remained unaltered in response to Put and declined due to Spd and Spm (> or = 0.1 mM). However, all PAs, irrespective of their individual effects, generally antagonized the ABA-dependent increase in CAT activity. Data indicate the possibility of ABA-PA interaction in the regulation of mitosis.

Polyamines in human breast cancer, effects of an anticancer drug

The polyamines putrescine, spermidine and spermine are ubiquitous amines, involved in cell growth and tumourogenesis. Their catabolism occurs via acetylation by Polyamine acetyl transferase [PAT], a cytosolic enzyme. Methyl glyoxal Bis [guanyl hydrazone] MGBG, is an antineoplastic agent known to inhibit polyamine biosynthesis. We studied the effect of MGBG on cell growth, polyamine content and PAT enzyme in ZR-75-1 cells a breast cancer cell line in culture. The cells were grown in monolayer for up to 120h. Twe cell growth was determined by estimating total protein content by the method of Lowry et al [1951]. Polyamines were analysed using reversed phase high performance liquid chromatography. PAT activity was assayed using [H]3 acetyl CoA and spermidine [3mM] as substrate. PAT activity was significantly increased [P <0.001] in MGBG-treated cells. It could be that MGBG exerts its cytotoxic effect on breast cancer cells by induction of their catabolism along with inhibition of their biosynthesis