[Formation of pyridine hemochromogen from protohemin methylester]

Fluorescent lipid oxidation products and heme spectra index antioxidant efficacy in kidney tissue of hamsters

Studies ranging from epidemiological to molecular suggest that dietary antioxidants protect against chronic diseases. The hypothesis was investigated that hamster kidney homogenate are better protected against induced oxidative damage after animals were fed a purified vitamin E deficient diet supplemented with 30 international units (IU) vitamin E/kg (30 IU diet) than fed the minimum required 3 IU vitamin E/kg (3 IU diet). The addition of 200 mg (+)-catechin to the 3 IU diet may offer protection. The effects of dietary (+)-catechin and alpha-tocopherol on tissue oxidizability were investigated by measuring (i) fluorescent products in lipid extracts, (ii) heme protein oxidation and (iii) heme destruction. A rapid initial increase of oxidation markers was measured over the 4 h incubation period for iron + ascorbate induced oxidation and a constant increase for lipoxygenase catalyzed products. Analysis of covariance over time and comparison at specific incubation times showed that iron + ascorbate induced homogenates from hamsters fed the 30 IU diet generated less fluorescent products and oxidized heme proteins than homogenates from the 3 IU or the 3 IU plus (+)-catechin fed animals. Incubation with lipoxygenase produced more lipid fluorescent products and heme protein oxidation in the 3 IU than in the 30 IU vitamin E group. In conclusion, supplementary dietary vitamin E but not supplementary (+)-catechin in a diet containing the minimum requirement of vitamin E for the species enhances oxidative resistance of kidney tissue.

Measuring the oxidation of heme compounds in heart homogenates from rats supplemented with dietary antioxidants

Protection by antioxidant nutrients against oxidative damage in rat heart homogenates was studied. Following spontaneous oxidation of heart homogenates from rats fed vitamin E, selenium, or beta-carotene, oxidized heme proteins (OHP) and thiobarbituric acid reactive substances (TBARS) were measured. The absorbance spectra of oxidized and reduced heme proteins were analyzed with a heme spectral analysis program (HSAP) developed in this laboratory. HSAP is a multicomponent analysis program that uses successive approximations and computer spread-sheet solver functions to deconvolute a complex absorbance spectrum into individual heme protein spectra. Vitamin E markedly decreased formation of OHP, and vitamin E, selenium, or beta-carotene significantly lowered the production of TBARS during spontaneous oxidation of heart homogenates compared with homogenates from rats fed antioxidant-deficient diets. Pyridine hemochrome analysis showed that the total amounts of heme proteins present in the homogenates decreased during the oxidative incubation period. The formation of OHP correlated significantly with the amount of TBARS produced and could be simulated as a function of the oxidative and protective reactions involved in the oxidation of rat heart homogenates.

Effects of haem infusion on biliary secretion of porphyrins, haem and bilirubin in man

Employing a continuous bile collection, we measured the bile secretion of porphyrins, haem (iron protoporphyrin IX regardless of oxidation state) and bilirubin in five healthy subjects. The baseline values for the flow of porphyrins in the bile were: 4.7 +/- 1.9 nmol/h uroporphyrin, 27.3 +/- 3.8 nmol/h coproporphyrin and 39.2 +/- 11.7 nmol/h protoporphyrin. Bile haem flow was 59.7 +/- 12.6 nmol/h, and that of bilirubin 23.8 +/- 8.2 mumol/h. Following haem injection (6.4 mumol/kg) the flow of protoporphyrin but not of the other porphyrins was reduced, and the bile haem flow increased (232 +/- 109.5 nmol/h), while the flow of bilirubin did not increase significantly. A few patients with representative porphyrias showed the expected increase in copro- and protoporphyrin in the bile. The patient with coproporphyria exhibited a bile flow of coproporphyrin of 1470 +/- 133 nmol/h and of protoporphyrin of 334 +/- 29 nmol/h; haem infusion significantly reduced the bile flow of both porphyrins (to 649 +/- 101 for copro- and 215 +/- 36 nmol/for protoporphyrin). The patient with protoporphyria had an increased protoporphyrin flow, yet haem infusion caused no reduction in protoporphyrin flow (106 +/- 7 after v. 81.4 +/- 13 nmol/h before haem). In conclusion, we found that haem and porphyrins are normal constituents of bile, and that injected haem appears in bile. Bile bilirubin did not rise within 12 h after haem infusion a finding which warrants further investigation.