Interaction of ascorbate with the radioprotective effect of mercaptoethylamin. An exploratory study in mice, whole animals and cell cultures

Testicular and plasma ascorbic acid levels in mice following dietary intake: a high-performance liquid chromatographic analysis

A modified buffer system is reported for the analysis of vitamin C in mouse plasma and testes, on a reversed-phase high-performance liquid chromatographic column with ultraviolet detection. The buffer, consisting of 0.1 M NaH2PO4 and 0.2 mM Na2EDTA adjusted to pH 3.1 with orthophosphoric acid, resolved the ascorbic acid (AA) peak allowing clear quantitation of the chemical. The method is also applicable to the assay of dehydroascorbic acid after its reduction to ascorbic acid, and overcomes problems of AA stability encountered in previously reported procedures. Using the present technique, variations in the vitamin levels of plasma and testes are studied from 3 to 29 days after the commencement of feeding a vitamin C-rich diet (1%, w/w) in mice. The plasma AA levels were elevated above the controls by a factor of 2.5 by day 8. Contrary to this, testicular AA levels increased marginally (1.2-fold) by day 12 and were maintained at levels close to the control values thereafter. It appears that the feedback inhibition mechanism which is effective in plasma is not operational in the testes. The findings are of clinical significance in that testicular AA levels do not change significantly as a result of dietary intake of vitamin C, whereas plasma AA levels do show an increase.

Inhibition of recA induction by the radioprotector 2-mercaptoethylamine

Our earlier finding that the radioprotective action of 2-mercaptoethylamine (MEA) is counteracted by ascorbate suggests a biochemical mechanism of action, which is supported by observations that MEA is not radioprotective in Rec- E. coli strains. In this study we show that MEA inhibits the induction of the recA gene by UV- or gamma-irradiation or by nalidixic acid in Escherichia coli strain GE94, which contains a recA-lacZ fusion. This effect, which may be counteracted by cysteine, indicates that in general MEA inhibits the induction of SOS functions.

Suppressing effect of cysteamine on the TSH-stimulated mitotic activity of the rat thyroid follicular cells in vivo

We have examined the effect of the thiol agent-cysteamine, known to deplete the hypothalamus, the pancreas, the gut of somatostatin--on the basal and TSH-stimulated mitotic activity of the thyroid follicular cells (TFC) in adult male rats in vivo. The animals of different groups were administered cysteamine alone (300 mg/kg BW, s.c.), TSH alone (2IU, i.p.), or cysteamine with TSH jointly, the former agent being injected 2 hrs prior to the latter. In order to evaluate the thyroid mitotic activity, the metaphase-arrest technique was used in the study. It was shown that: 1. TSH significantly increased the mitotic activity of TFC, as compared to controls, 2. cysteamine alone had no effect on the TFC proliferation, 3. unexpectedly, cysteamine, when administered 2 hrs prior to TSH, suppressed the stimulatory effect of TSH on the mitotic activity of TFC.

Iron release from ferritin and lipid peroxidation by radiolytically generated reducing radicals

Iron is involved in the formation of oxidants capable of damaging membranes, protein, and DNA. Using 137Cs gamma radiation, we investigated the release of iron from ferritin and concomitant lipid peroxidation by radiolytically generated reducing radicals, superoxide and the carbon dioxide anion radical. Both radicals released iron from ferritin with similar efficiencies and iron mobilization from ferritin required an iron chelator. Radiolytically generated superoxide anion resulted in peroxidation of phospholipid liposomes as measured by malondialdehyde formation only when ferritin was included as an iron source and the released iron was found to be chelated by the phospholipid liposomes.