Heme Oxygenase Activity and Heme Binding in a Neonatal Mouse Model.

BACKGROUND: Severe hemolytic disease of the newborn leads to the release of pro-oxidative free heme (FH). Heme oxygenase (HO) is primarily responsible for detoxifying FH. OBJECTIVE: To investigate the protective effects of HO in a model of heme overload. METHODS: For in vitro studies, NIH3T3 HO-1-luc cells were incubated with 10, 30, or 60 µM FH or methemalbumin (MHA). HO-1 promoter activity was assessed 3, 6, and 24 h after treatment. Cell survival was indexed by viability assays. For in vivo studies, 1- and 5-week-old wild-type (Wt) or HO-1-heterozygous (Het, HO-1+/-) mice were given 60 µmol FH or MHA/kg intraperitoneally. After 24 h, plasma aspartate aminotransferease (AST)/alanine transaminase (ALT) and hemopexin, liver HO activity, and lipid peroxidation (LP) were determined. RESULTS: In HO-1-luc cells, HO-1 promoter activity peaked 6 h after incubation with 30 µM FH (1.6-fold) or 60 µM MHA (2.1-fold) over baseline. Twenty-four hours after exposure to 60 µM FH, a decrease in viability of 80% was found, compared with no decrease after exposure to 60 µM MHA. In 1-week-old Wt and HO-1 Het pups given 60 µmol FH/kg, HO activity significantly increased 3.5- and 3.1-fold, respectively. No changes in LP or AST/ALT levels were observed. In adult Wt and HO-1 Het mice, HO activity increased (3.0- and 2.6-fold, respectively). LP and AST levels significantly increased 28.4- and 2.7-fold, respectively, in adult HO-1 Het mice. Hemopexin levels at baseline were higher in adults compared with newborns for both Wt and Het mice. In addition, FH induced hemopexin levels in both adults and newborns, but to a lesser degree in newborns. CONCLUSIONS: FH is highly toxic in vitro, but its toxicity is abolished when bound to albumin. Newborns appear to be protected from the pro-oxidative effects of FH, which may be mediated by heme binding and a higher absolute HO activity at baseline and after FH-mediated induction.

Increased erythrocyte deformability in fetal erythropoiesis and in erythrocytes deficient in glucose-6-phosphate dehydrogenase and other glycolytic enzymes.

Erythrocyte deformability was determined in more than 500 clinical samples, and was found to be elevated in conditions in which fetal-like red cells are produced: aplastic anemia (3/3 cases), myelodysplastic syndromes, polycythemias, sickle cell anemia during treatment with hydroxyurea, paroxysmal nocturnal hemoglobinuria, and recovery from B12 deficiency. Elevated deformability was observed in neonatal erythrocytes, and during recovery from transient erythroblastopenia of childhood, when fetal-like red cells are known to be produced. Increased deformability appears to be a feature of fetal and fetal-like red cells. Forty-eight cases of enzymatically verified glucose-6-phosphate (G-6-PD) deficiency were also examined. Thirty out of 32 G-6-PD(A-) individuals, including both heterozygotes and hemizygotes, exhibited increased deformability during the steady state. In contrast, G-6-PD(Med) hemizygotes had normal deformability. Increased deformability was also found in G-6-PD(Huron) (n=3), G-6-PD(Wayne) (n=4), triose phosphate isomerase deficiency (n=2), and pyruvate kinase deficiency (n=2). An elevated osmoscan was found in more than 90% of female G-6-PD heterozygotes, affording a simple screening test for heterozygotes. Deformability remained high during hemolytic episodes, when older enzyme deficient cells are removed from the circulation. In four cases of G-6-PD deficiency with normal deformability, evidence for co-existing hereditary spherocytosis was found. The combination of conditions with opposing effects on deformability resulted in nearly normal deformability. Because increased red cell deformability is a feature of fetal erythrocytes, these results suggest that the red cells in many cases of glycolytic enzyme deficiency are fetal-like.

[Oxytocinase: levels in normal and pathological pregnancies]. / Ocytocinase: valeurs au cours de la grossesse normale et pathologique.

The author has determined the levels of plasma oxytocinase in a series of normal and pathological pregnancies. It appears from studying these levels that it is useful to measure the oxytocinase particularly in cases where there is failure of intra-uterine growth.

[Activity and isoenzyme composition of lactate dehydrogenase and malate dehydrogenase in the blood and erythrocytes of newborn children with hemolytic disease]. / Aktivnost' i izofermentnyi sostav laktatdegidrogenazy i malatdegidrogenazy v syvorotke krovi i éritrotsitakh novorozhdennykh detei s gemoliticheskoi bolezn'iu.

Activities of lactate dehydrogenase (LDH) and NAD-dependent malate dehydrogenase (MDH) were considerably increased in blood serum of healthy children within the first 10 hrs after their birth. Content of LDH4 and LDH5 isoenzymes was increased, along with a decrease in LDH1 content, in blood serum. Differences in LDH isozyme spectra between blood serum and hemolysate in healthy newborns became more distinct within the perinatal period. In blood serum of newborns with hemolytic disease high activity of LDH and MDH was found immediately after birth. As distinct from healthy children, high content of LDH1 and very low concentrations of LDH4 and LDH5 were observed in blood serum of the impaired children within the perinatal period. The dissimilarity in LDH spectra became less distinct in blood serum and hemolysate of children with hemolytic disease. The composition of MDH isoenzymes was not distinctly altered in blood serum and hemolysate of both healthy and impaired newborn children within the perinatal period.

The value of amniotic fluid diamine oxidase estimations in the management of severe rhesus iso-immunization.

Serial estimations of the enzyme, diamine oxidase (D.A.O.) in liquor amnii were made in 82 rhesus sensitised women. Normal levels were found in severe disease with a favourable fetal outcome, but abnormal levels were found in 50% of the pregnancies in which severe disease was associated with fetal death. In addition, when liquor bilirubin levels predicted moderate-severe disease, D.A.O. levels were abnormal in 75% of the pregnancies in which the fetus succumbed. Abnormally low D.A.O. levels in amniotic fluid were frequently associated with the subsequent development of disseminated intra-vascular coagulation in the infant. Serial estimations of D.A.O. in amniotic fluid could be a helphful adjunct to serial liquor bilirubin estimations in the management of severe rhesus iso-immunisation.