Glutathione peroxidase, selenium, and prostaglandin synthesis in platelets

Abstract

Glutathione peroxidase (GSH-Px) contains 4 selenium atoms/molecule; its activity is increased by selenium dietary intake. The enzyme destroys H2O2 and organic hydroperoxides, contributing to the integrity of biological membranes. GSH-Px activity increased (+100%) in washed platelets of rats administered selenium (0.3 ppm given as sodium selenite) for 60 days from 10.44 +/- 1.10 U/g protein (control rats fed a standard diet) to 20.50 +/- 1.21 U/g protein (mean +/- SE; P less than 0.001). GSH-Px in washed erythrocytes was also stimulated (+70%) after 80 days of selenium dietary intake from 11.60 +/0 0.82 U/g Hb to 19.74 +/- 0.94 U/g Hb (P less than 0.001). Malondialdehyde (MDA), the typical breakdown product of peroxidized lipid and a suitable indicator of platelet prostaglandin production, increased from 0.343 +/- 0.035 nM/3 X 10(8) platelets (control) to 0.478 +/- 0.052 nM/3 X 10(8) platelets after 30 days of selenium treatment (P less than 0.05) and to 0.527 +/- 0.051 nM/3 X 10(8) platelets after 80 days (P less than 0.01). MDA was measured by the thiobarbituric acid method after stimulation with 25 X 10(-4) M arachidonic acid. It is concluded that platelets are very rich in GSH-Px, i.e., activity is greatly increased by oral administration of selenium and that the synthesis of prostaglandins is stimulated too.

Regulation of vascular prostaglandin synthesis by metabolites of arachidonic acid in perfused rabbit aorta.

“…Our data do not, however, indicate whether a "critical level" of arachidonate metabolism exists below which antioxidant mechanisms are sufficient to prevent oxidative enzyme damage, or whether this level can be modified by antioxidant treatment. Previous studies of the effects of antioxidants on arachidonic acid metabolism have yielded variable results, depending on tissue, species, and specific antioxidant (18,21,33,(35)(36)(37)(38)(39)(40). This finding is not surprising given the potential of oxidative intermediates to both stimulate and inhibit the enzymes of the arachidonic acid cascade.…”

Glutathione Peroxidase Blockage Inhibits Prostaglandin Biosynthesis in Rat Platelets and Aorta

“…GSH-Px activity dosage was performed in washed and lysed erythrocytes, as previously described [6] by using tert-butyl-peroxide as reaction initiator.…”

“…Platelet malondialdehyde (MDA) production was measured with the thiobarbiturate method, as pre viously described [6].…”

“…It is present in various mamma lian tissues, including erythrocytes [4], blood platelets [6], and arterial vessel wall [11],…”

“…It was suggested that, together with other per oxidases, the enzyme is implicated in prosta glandin production catalyzing the reaction: PGG2-» PGH2 [9] and HPETE-> HETE [1], Recent investigations also support the view that antioxidants have a physiological effect on arachidonic acid metabolism [3,6]. This study presents new lines of evidence on the connection between GSH-Px activity and prostaglandin production in rat platelets and arterial vessel wall by using an inhibitor: 3-amino-1,2,4-triazole (AMT).…”