Hepatic function tests in children with sickle cell anaemia during vaso occlusive crisis

Thirty children with sickle cell anaemia had their serum alanine aminotransferase, alkaline phosphatase, total protein, albumin and bilirubin, assayed during vaso-occlusive crisis and at recovery. Alanine aminotransferase, alkaline phosphatase and bilirubin levels were significantly higher during crisis than at recovery, (p < 0.005) especially in the young patient. However, the total protein and albumin levels were not significantly different in crisis and at recovery. A transient hepatic functional derangement during vaso-occlusive crisis is a probable explanation for the reported changes.

Increased activity of 5' nucleotidase in serum of patients with sickle cell anaemia

Fifty-nine patients with homozygous sickle cell anaemia, 17 heterozygous individuals and 22 controls were investigated in respect to serum (S) 5'nucleotidase (5'NT, EC 3.1.3.5). The patients showed a significantly higher mean value of S-5'NT compared to the controls. However, this rise was heterogeneous as it occurred only among a subgroup of patients. The heterozygous individuals were not different from either the patients or the controls generating a situation which puts the heterozygous individuals in an intermediate position between the patients and the controls. S-5'NT showed significant correlation with S-bilirubin, S-aspartate aminotransferase, S-alanine aminotransferase and especially S-gammaglutamyl transferase. However, it was not correlated with S-alkaline phosphatase, which is another marker for hepatobiliary disease. These results suggest that the liver involvement in a subgroup of patients with sickle cell anaemia is a mixture of hepatocyte damage and the biliary tree involvement.

Prenatal diagnosis of sickle cell anemia using PCR and restriction enzyme Dde I

Prenatal diagnosis of sickle cell anemia was carried out in four fetuses using DNA technology. Fetal chorionic villus specimen were obtained at the 10th week of pregnancy from women at risk of giving birth to children with sickle cell anemia. Whole cellular DNA was obtained and the part of the DNA presumed to have a mutation increased after PCR was performed. After the application of Dde I restriction enzyme, mini gel electrophoresis was performed. The study of the electrophoretic patterns of the DNA indicated that one of the four fetuses was unaffected, one was a carrier and the remaining two were affected.

[Fatal course of a sequestration crisis in hemoglobin SC disease]

A 14 year-old patient developed severe anemia and splenomegaly 2 days after the onset of a febrile upper airway infection. The hemoglobin concentration had dropped to 1.1 g/dl. Death occurred as consequence of the acute anemia and peripheral circulatory failure. The crisis was caused by an acute splenic sequestration. Hemoglobin SC disease could be identified as the underlying disorder. Hemoglobin SC disease usually has a milder course than sickle cell disease. However the patients may develop the same crisis-like symptoms. Splenic sequestration is caused by the occlusion of the splenic sinuses due to sickled and aggregated erythrocytes with subsequent trapping of large blood volumes and circulatory failure. Regular transfusions and/or splenectomy are recommended to prevent splenic sequestration crisis.

Characterization of phosphoinositide kinases in normal and sickle anaemia red cells

PtdIns and PtdInsP kinases from normal erythrocyte (AA) membranes and sickle cell anaemia erythrocyte (SS) membranes have been characterized. PtdIns kinase was studied in native membranes under conditions in which PtdInsP kinase and PtdInsP phosphatase do not express any activity. Kinetic analysis of the AA and SS PtdIns kinases indicate similar Km values for PtdIns and ATP but higher Vmax values for SS PtdIns kinase. PtdInsP kinase was partially purified from erythrocyte ghosts by NaCl extraction. The kinetic parameters of PtdInsP kinase determined under these conditions were similar in AA and SS NaCl extracts. These data suggest the presence of some effector of PtdIns kinase in SS cell membranes, resulting in a greater activity of the enzyme. This leads consequently, to increase the PtdIns4P pool and to activate PtdInsP kinase, in agreement with our previous observations of a greater [32P]Pi incorporation in both polyphosphoinositides in SS cells relatively to AA cells.

Increased membrane activity of glyceraldehyde 3-phosphate dehydrogenase in erythrocytes of patients with homozygous sickle cell anaemia

Membrane-bound glyceraldehyde 3-phosphate dehydrogenase activity was measured in erythrocytes from 43 patients with sickle cell anaemia, 24 heterozygous and 27 controls. A significant increase of the activity was found among the patients but no such difference was observed between the heterozygous and the control individuals. The patients showed nearly non Gaussian distribution of the enzyme activity and were subgrouped on the basis of these results, subgroup I had normal values and subgroup II showed markedly increased activities. The patients in subgroup II had significantly lower blood haemoglobin concentrations and significantly higher lactate dehydrogenase activities in serum than subgroup I. The subgroups did not differ in blood reticulocyte counts, serum bilirubin, serum iron concentrations or band 3 protein content of erythrocyte membranes.

Pedigree analysis and involvement of peroxidase in sickle cell disease

Routine hematological tests were performed in a family which was at risk for sickle cell disease. Cellulose acetate electrophoresis and Triton PAGE were employed to differentiate between various variants of hemoglobin. Based on the data a pedigree was constructed which indicated that few members of the respectively had received the S gene, some of them were sickle cell disease while few were sickle cell trait. Elevated levels of peroxidase enzyme in affected individuals reflect its involvement in RBCs destruction. Statistical analysis strengthen this statement.

Decreased pyrimidine nucleoside monophosphate kinase activity in sickle erythrocytes

We have previously shown that physiologic concentrations of hemin cause marked inhibition of several red blood cell (RBC) enzymes. Because endogenous heme content is elevated in sickle RBCs, we have examined the activity of hemin-sensitive enzymes in these RBCs. One of the hemin-sensitive enzymes, pyrimidine nucleoside monophosphate kinase (PNMK), was shown to have decreased activity in sickle RBCs relative to RBCs of equivalent cell age. The other hemin-sensitive enzymes, including adenylate kinase (AK), pyrimidine 5'-nucleotidase (P5N), 6-phosphogluconate dehydrogenase (6PGD), and aldolase, had activities that were appropriate for cell age. We have also examined the affinity of the hemin-sensitive enzymes to hemin. Using two different methods, PNMK was shown to have the highest binding affinity to hemin. The exquisite sensitivity of PNMK to inhibition by hemin, coupled with the enzyme's high affinity to hemin, may account for the decrease in PNMK activity and the lack of significant decrease in the other hemin-sensitive enzymes in sickle RBCs. These results suggest that the increased endogenous heme content in sickle RBCs may be responsible for the decrease in PNMK activity. Whether the increased endogenous heme content of sickle RBCs can cause hemolysis indirectly by inhibiting RBC enzymes remains to be determined.

Ca2+ accumulation and loss by aberrant endocytic vesicles in sickle erythrocytes

Sickle cells contain internal vesicles which accumulate Ca2+. As shown here, the membrane enclosing the vesicles contains the plasma membrane Ca(2+)-ATPase, or Ca2+ pump, as judged by staining with an antibody directed against the protein. Moreover, the number of cells containing such vesicles increases upon deoxygenation. These findings argue strongly that the vesicles arise by endocytosis from the plasma membrane, and explain how they accumulate Ca2+. When sickle cells are depleted of ATP, Ca2+ is lost from the vesicles, as judged by the disappearance of staining with the Ca2+/membrane probe chlortetracycline (CTC), without a corresponding loss of antibody staining. This loss of Ca2+ can be inhibited by nitrendipine, a Ca2+ channel blocker. These results suggest that the vesicle membrane allows outward passage of Ca2+ by a nitrendipine-sensitive pathway, which can be overcome by the inward-directed activity of the Ca2+ pump of the vesicle membrane. If so, the Ca2+ which vesicles contain is in dynamic equilibrium with the cytoplasm of the sickle erythrocyte.

Erythrocyte fructose 2,6-bisphosphate content in congenital hemolytic anemias

We have investigated the levels of fructose 2,6-bisphosphate and its synthesizing enzyme 6-phosphofructo-2-kinase in red blood cells from different congenital anemias. Fructose 2,6-bisphosphate concentration and 6-phosphofructo-2-kinase activity are markedly influenced by the number of reticulocytes in all the cases studied with the exception of homozygous pyruvate kinase deficiency, where no correlation was observed with the percentage of reticulocytes.

Erythrocyte membrane enzymes in sickle cell anemia. 2. Acetylcholinesterase and ATPase activities

The activity level of acetylcholinesterase in the erythrocytes of 32 patients homozygous for sickle cell anemia was determined and compared with that of normal AA controls as well as with that of AS individuals. Acetylcholinesterase activity was markedly higher in erythrocyte membrane from SS individuals than in those from AS individuals or AA controls. Additionally, ATPase activities were also significantly higher in sickle cell erythrocytes as compared to normal cells. These higher values of acetylcholinesterase and ATPase activities in SS erythrocytes may be explained as a consequence of the abnormally high cation levels in sickle cell erythrocytes.

Impaired erythrocyte methemoglobin reduction in sickle cell disease: dependence of methemoglobin reduction on reduced nicotinamide adenine dinucleotide content

We have examined aspects of methemoglobin (metHb) reduction in sickle and in thalassemic red blood cells (RBCs). NADH metHb reductase activity in sickle and thalassemic RBCs was significantly increased compared with normal RBCs. Because in vitro enzyme activity does not necessarily represent in vivo activity, we measured the rate of metHb reduction in intact RBCs. Intact thalassemic RBCs demonstrated a significantly increased rate of metHb reduction compared with normal RBCs. In contrast, intact sickle RBCs had a rate of metHb reduction that was similar to normal RBCs and significantly decreased relative to high reticulocyte RBCs of equivalent cell age. To determine the mechanism for the relative impairment of metHb reduction in sickle RBCs, we measured intraerythrocytic NADH, a cofactor in the metHb reduction reaction. Thalassemic RBCs had a significantly increased NADH content relative to normal RBCs. In contrast, sickle RBCs did not have an increase in NADH content. Furthermore, incubating normal RBCs under conditions that increase the NADH content resulted in an increased rate of metHb reduction. In contrast, conditions that decrease the NADH content in normal RBC resulted in a decreased rate of metHb reduction. These data and other results suggest that metHb reduction in intact RBCs is dependent on NADH content, and that the impaired metHb reduction rate in sickle RBCs may be a result of a lack of increase in NADH content. The dependence of metHb reduction on RBC NADH content and the ability to manipulate NADH content in vitro suggest a new strategy for decreasing oxidant damage to sickle RBCs in vivo.

Selenium and glutathione peroxidase levels in sickle cell anemia

Levels of plasma selenium (Se) and glutathione peroxidase were measured in 20 sickle cell anemia (SCA) patients not in crisis and in 14 nonanemic control subjects. The results show that the levels of Se and glutathione peroxidase were significantly (p less than 0.005) lower than those of controls in both plasma and whole blood. These data are consistent with the previous reports that there is increased oxidative stress in SCA. Low blood Se levels and glutathione peroxidase activity observed in this research suggest that a weakened antioxidant potential may be associated with SCA patients. The low Se status in SCA patients may also affect the phenotypic expression of these patients.

Erythrocyte membrane Ca2+ ATPase: reactivities of human A, AS, and S erythrocytes with steroid hormones

In a preliminary study we reported a significant enhancement of Ca2+ ATPase activity in sickle cell membranes in the presence of progesterone and testosterone. In this work the reactivity of various classes of steroid hormones with the membranes of hemoglobin variants was investigated. A consistent universal stimulation of Ca2+ ATPase activity in sickle cell membranes by the different classes of steroid hormones does not appear to correlate with any major structural differences of the hormones or the presence of reactive functional groups. The universal interaction of the hormones with sickle cell membranes probably enhances Ca2+ efflux through the Ca2+ ATPase without directly affecting the characteristics of the pump.

Sequestrocytes: a manifestation of transcellular cross-bonding of the red cell membrane in sickle cell anemia

An unusual form of red cells (called sequestrocytes) that circulate in the peripheral blood of patients with sickle cell anemia has been identified. In wetmount light microscopy preparations, sequestrocytes appear as massively vacuolated erythrocytes. We have shown by transmission electron microscopy and scanning electron microscopy that the morphology of sequestrocytes can be accounted for on the basis of transcellular cross-bonding of the cell membrane. Initially, endocytotic vesicles span the cytoplasmic space, forming putative cytoskeletal fusion zones. Points of fusion of the membrane skeleton bridging the cytoplasmic compartment expand laterally to form linear fusion zones that entrap lakes of hemoglobin within pseudovacuoles. Sequestrocytes can be isolated in the densest layer (1.159 g ml-1 or greater) of an arabinogalactan density gradient. These cells can be generated in increased numbers in sickle cell blood by incubating samples in 1.5 mM-acetylphenylhydrazine (APH) solution for two hours at 37 degrees C. Their formation is partially blocked by incubation with the reducing agent, dithiothreitol (DTT). Our results suggest that these cells represent an expression of oxidative membrane injury in sickle cell anemia.

Alteration in protein kinase C activity and subcellular distribution in sickle erythrocytes

In agreement with previous data, membrane protein phosphorylation was found to be altered in intact sickle cells (SS) relative to intact normal erythrocytes (AA). Similar changes were observed in their isolated membranes. The involvement of protein kinase C (PKC) in this process was investigated. The membrane PKC content in SS cells, measured by [3H]phorbol ester binding, was about 6-times higher than in AA cells. In addition, the activity of the enzyme, measured by histone phosphorylation was also found to be increased in SS cell membranes but decreased in their cytosol compared to the activity in AA cell membranes and cytosol. The increase in membrane PKC activity was observed mostly in the light fraction of SS cells, fractionated by density gradient, whereas the decrease in cytosolic activity was only observed in the dense fraction. PKC activity, measured in cells from the blood of reticulocyte-rich patients, exhibited an increase in both membranes and cytosol, thus explaining some of the effects observed in the SS cell light fraction, which is enriched in reticulocytes. The increase in PKC activity in the membranes of SS cells is partly explained by their young age but the loss of PKC activity in their cytosol, particularly in that of the dense fraction, seems to be specific to SS erythrocytes. The relative decrease in membrane PKC activity between the dense and the light fractions of SS cells might be related to oxidative inactivation of the enzyme.

Creatine kinase activity in sickle cell disease

Creatine kinase activity was measured in 28 patients in the steady state of sickle cell disease and ranged from 4-45 IU/l, comparable with that found in healthy adult caucasians. Creatine kinase activity was also measured in 14 patients admitted consecutively for the treatment of vaso-occlusive sickle cell crises. Creatine kinase activity remained within the normal range in eight of these 14 patients throughout their admission; none had muscle pain or a chest syndrome. In the remaining six, three with muscle pain and three with a chest syndrome, increased activity was found on one or more days. A further 17 patients with vaso-occlusive sickle cell crises, associated with muscle pain, were studied. Creatine kinase activity was significantly raised in all 17, the mean creatine kinase activity for men was 578.8 IU/l and 210.6 IU/l for women, with the highest values (up to 1790 IU/l) found in those who had exercised before admission. Measurement of creatine kinase activity may therefore be a useful marker of muscle perturbation due to sickling.

Red cell membrane phosphatidylinositol kinase activity in hemolytic anemias and myeloproliferative diseases

Phosphatidylinositol kinase activity was determined in red cell membranes from 85 healthy individuals, 20 patients with hereditary hemolytic anemia and 24 patients with myeloproliferative disorder. Increased activity was found in all ten cases of sickle red disease and seven among ten cases of other hereditary hemolytic anemias. These increases had no correlation with the reticulocyte count nor with the red cell shape. An unexpected decreased activity was found in several cases of myeloproliferative disorders, especially in polycythemia vera, with a negative correlation with the reticulocyte count. The mechanism(s) and significance of the phosphatidylinositol kinase abnormalities in these different groups of diseases remain to determine.

Endogenous calcium in sickle cells does not activate polyphosphoinositide phospholipase C

Sickle-cell-anaemia erythrocytes (SS cells) are known to have a high Ca2+ content (particularly the dense cell fraction) and to take up Ca2+ on deoxygenation. It has been reported that this high Ca2+ was responsible for the activation of the Ca2+-dependent K+ loss, and of the Ca2+-sensitive polyphosphoinositide phospholipase C (PIC) in dense SS cells. We found that, either in the total population of SS cells or in the light or dense fractions, the content of phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] was not changed, whereas that of phosphatidylinositol 4-phosphate was increased and that of phosphatidic acid (PtdOH) was decreased compared with normal (AA) erythrocytes. Deoxygenation-induced Ca2+ entry into SS cells did not change the concentration or, in 32P-prelabelled cells, the radioactivity of polyphosphoinositides and PtdOH. It also failed to induce the formation of inositol 1,4,5-trisphosphate, the product of PtdIns(4,5)P2 hydrolysis by PIC, which was measured by an original method using ion-pair reverse-phase h.p.l.c. Thus there was no evidence of an endogenous Ca2+ effect on the PIC activity in SS cells, in agreement with the demonstration that the excess Ca2+ in SS cells is compartmentalized into internal vesicles and unavailable as free Ca2+. The 32P incorporation in polyphosphoinositides and PtdOH was markedly higher in SS than in AA cells, but this increase was the same in both dense and light SS cells. The increase in the turnover of these phospholipids in SS cells is consistent either with an activation of the lipid kinases and phosphatases or with perturbation in the metabolic compartmentation of these lipids.

Tissue type plasminogen activator antigen and activity in sickle cell disease

To investigate the hypothesis that diminished endothelial fibrinolysis is present in sickle cell (SS) disease plasma, tissue type plasminogen activator (t-PA) antigen titres were measured before and after a standard stimulus of endothelial t-PA release (venous occlusion of the arm), and plasma t-PA activities after venous occlusion in 33 subjects with SS disease and in 32 healthy subjects. Mean plasma t-PA antigen titres before and after venous occlusion, and mean plasma t-PA activities after venous occlusion did not differ significantly between SS patients and normal subjects. No significant differences in mean t-PA antigen and activity were observed between samples taken from inpatients being treated for acute pain crisis (18 subjects, 30 samples) and samples taken from subjects in the steady state (23 subjects, 26 samples). No consistent differences were seen between painful crisis and steady state samples in eight SS patients studied while in crisis and in the steady state. No correlation was observed between any fibrinolytic variable in SS patients and the overall severity of microvascular occlusive disease as measured by a standard scoring system. It is concluded that the capacity of endothelium to synthesise and release t-PA is not impaired in SS disease, and that excessive inhibition of released t-PA, leading to reduced t-PA activity in plasma is also not a feature of SS disease, either in the steady state or during painful crisis.

Altered amount and activity of superoxide dismutase in sickle cell anemia

The amount and activity of superoxide dismutase (SOD) (EC 1.15.1.1) were measured in red cells collected from 50 white controls, 101 black controls, 50 patients with sickle hemoglobin (SS Hb), 12 with sickle trait, and 11 with other sickling hemoglobinopathies. Red cells from normal black subjects had more SOD amount and activity than normal whites (1.77 U/mg Hb and 2.96 micrograms/mg Hb vs. 1.47 U/mg Hb and 2.64 micrograms/mg Hb, respectively) or blacks with SS Hb or other sickling hemoglobinopathies. Patients with more severe manifestations of SS Hb had lower levels of SOD activity than those with milder symptoms but had the same amount of enzyme protein. Individuals with sickle trait had amounts and activities of SOD comparable to black controls. An alteration in defense to free radical oxygen may play a role in the severity of symptoms experienced by patients with homozygous sickle cell disease.

Variations in the relative activities of erythrocyte membrane ATPase with changes in severity of sickle cell anemia

Red blood cells from 31 patients with sickle cell anemia whose hemoglobins were ascertained as SS were assayed for Mg-, Ca-, Na-, and total ATPase activities. The ATPase activities were correlated with the various stages of severity in each patient as determined by clinical parameters. The results demonstrate that increases in ATPase activities were associated with increases in the percentage severity of sickle cell anemia. Severity correlated inversely with fetal hemoglobin levels in the sickle cell patients. ATPase activities were generally higher in SS genotypes than in AS and AA normal individuals.

Increased membrane-associated phorbol-12,13 dibutyrate (PDBu) receptor function in sickle red cells

A four-fold increase in the binding of 3H-PDBu by red cell membrane ghosts isolated from sickle red cells compared to that from normal controls is presented. Phosphorylation studies with gamma-32P-ATP indicate a similar (two to three-fold) increase in the radiolabelling of the acid-precipitable membrane proteins in sickle red cells. When red cells were loaded with Ca2+ using Ionophore A23187, both normal and sickle red cells enhanced their phosphorylation and sickle red cells to a greater extent than normal red cells. Polyacrylamide slab gel electrophoretic separation of the phosphoproteins and autoradiography also reveal phosphorylation, predominantly of protein bands 3, 4.1 and 4.9 which are known in the red cells as specific substrates for the PDBu receptor, protein kinase C. These results indicate that membrane association of protein kinase C in sickle red cells is increased, possibly as a consequence of the pathological change in their ability to accumulate intracellular calcium.

The prevalence of atypical serum cholinesterase in a Nigerian population

The prevalence of the atypical phenotype of pseudocholinesterase was looked for in 345 individuals living in Zaria district of Northern Nigeria by the differential inhibitory actions of dibucaine and sodium fluoride. The frequency of the atypical gene, Ea1 was found to be 0.9% and the frequency of the fluoride insensitive phenotype Ef1, was 0.74%. The atypical enzyme or the intermediate phenotype was not observed in any of the 42 patients with sickle-cell disease.

Serum enzymes of collagen synthesis and type III procollagen aminopropeptide in Nigerian patients with sickle cell disease

Serum immunoreactive prolyl hydroxylase protein (S-IRPH), galactosylhydroxylysyl glucosyltransferase activity (S-GGT), and the aminoterminal propeptide of type III procollagen (S-Pro(III)-N-P) were measured in 20 patients with sickle cell disease and the values were compared with those in 20 apparently healthy Nigerians. The means for the two enzymes and S-Pro(III)-N-P were significantly elevated in the sickle cell disease patients. Significant correlations were found between the values of the two enzymes and the protein (S-Pro(III)-N-P) within the sickle cell disease patients. The data confirm that collagen formation is found in the bone, liver, or other organs of patients with this disease. The measurement of S-GGT and S-Pro(III)-N-P in prospective studies might be helpful in predicting general and hepatic fibrogenesis in sickle cell disease.

Serum ferritin concentration in sickle cell crisis

Serum ferritin, aspartate aminotransferase (AST), alkaline phosphatase and hydroxybutyrate dehydrogenase (HBD) were studied during 21 vaso-occlusive crises in 12 adults with sickle cell disease (11 SS, 1 S beta degrees). The patients comprised three groups: those who had been untransfused (4), those who had received occasional exchange transfusion in crisis (3), and those who had been multiply transfused (5). Serum ferritin concentrations in crisis were compared with those of the steady state value. Rises in serum ferritin concentrations occurred in all crises in all groups. Although AST, alkaline phosphatase, and HBD rose, there was no correlation between these and log ferritin concentrations. The clinical impression was that the degree of rise in ferritin related to the severity of the particular crisis, and the above results showed that haemolysis and liver damage were not causally related to this rise. An estimate of serum ferritin cannot be used to assess the state of iron balance in sickle cell disease unless the patient is in the steady state. The considerable rise in serum ferritin concentration found in crisis, however, may be a useful marker of the extent of vaso-occlusion and tissue damage.

Tissue damage in sickle cell disease as assessed by serum acid phosphatase

The extent of tissue damage caused by vaso-occlusion in sickle cell disease in those organs rich in acid phosphatase was assessed by measuring serum acid phosphatase in 33 patients with homozygous sickle cell disease Hb-SS (sicklers) and comparing the result with that of 31 persons with normal haemoglobin-AA (non-sicklers) matched for age and sex. The result showed a decrease in the level of total, labile and tartrate-resistant serum acid phosphatase in sicklers compared to non-sicklers, though the decrease is not statistically significant (p greater than 0.1). Though serum acid phosphatase is unlikely to be a useful index for the assessment of organ damage, the result is in consonance with reported decreases in other body secretions such as serum testosterone or aldosterone due to organ damage by vaso-occlusion of the micro-circulation by sickled red cells in sickle cell disease.

Association of red cell glucose-6-phosphate dehydrogenase with haemoglobinopathies

A total of 1,112 randomly selected Saudi Arabs, of both sexes, living in Jeddah and the surrounding areas were screened for the phenotypic distribution of red cell glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD). They were also investigated for haemoglobin and for thalassaemia. Phenotyping of the haemoglobins and the red cell enzymes was carried out by starch gel electrophoresis and the dye-decolouration screening test, while the investigation for thalassaemia was carried out by globin-chain biosynthesis, followed by column chromatography. The red cell Gd- alleles were significantly associated with the sickle-cell gene in both the males (chi 2(1): AS-28.80; SS-4.89) and females (chi 2(1): AS-10.99; SS-13.16). A similar association was also observed between G6PD deficiency and thalassaemias in males (chi 2(1): alpha-thalassaemia - 3.13; beta-thalassaemia - 11.06) and females (chi 2(1): alpha-thalassaemia - 6.63). However, no such association was detected between red cell 6PGD types and haemoglobin genes. The results suggest that the red cell G6PD deficiency, sickle-cell and thalassaemia genes might have evolved as a result of the same ecological factor, probably malaria.

Sickle-cell membrane-bound (Ca2+ + Mg2+)-ATPase: activation by 3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-6-butyric acid, a novel antisickling agent

The effects of 3,4-dihydro-2,2-dimethyl-2H-1-benzopyran-6-butyric acid (DBA), an antisickling agent, on the rates of Ca2+-dependent ATP hydrolysis by the human red cell (Ca2+ + Mg2+)-ATPase, have been studied in membranes (normal and sickle-cell) stripped of endogenous calmodulin. The activity of the enzyme is increased by DBA in a manner which is dependent on both the concentrations of DBA and Ca2+. At 37 degrees C, the normal red cell (Ca2+ + Mg2+)-ATPase activity is stimulated maximally by 133% in the presence of 1 mM DBA and 0.2 mM CaCl2, while the sickle-cell enzyme is stimulated maximally by 81% in the presence of 0.5 mM DBA and 0.2 mM CaCl2. The stimulation of the enzyme in both systems is antagonized by increasing the CaCl2 concentration in the medium to 0.5 mM, in contrast to the well established mode of activation by the modulator protein, calmodulin. This suggests that the two effectors, DBA and calmodulin, probably act by different mechanisms. From our present observations, we suggest that the antisickling effect of DBA may be connected with the mobilization of calcium within red cells.

Red cell superoxide dismutase and sickle cell anemia symptom severity

Patients with sickle cell anemia vary in the severity of their symptoms but the basis of this variability is unknown. We have tested the hypothesis that this variability is related to differences in the activity of the antioxidant superoxide dismutase (SOD). The amount of superoxide dismutase I (SOD) enzyme activity in red cells of patients with different degrees of symptom severity and healthy black and white controls was measured and correlated with symptom severity in SCA patients. Blacks with normal (AA) hemoglobin had significantly (p less than .001) more SOD activity (1.82 U/mg Hb) than white controls (1.44 U/mg Hb). Patients with moderate or severe symptoms had less SOD activity (1.16 and 0.95 U/mg Hb, respectively) than control blacks or SCA patients with mild symptoms (1.62 U/mg Hb). The correlation of SOD activity and symptom severity was not a function of age or sex and was unrelated to reticulocyte count or fetal hemoglobin level.

Erythrocyte porphobilinogen synthase activity as an indicator of lead exposure in children

The European standardized method for measuring porphobilinogen synthase (PBGS, EC 4.2.1.24) activity in peripheral erythrocytes is widely used in epidemiological studies of low-level Pb absorption. We have modified it to include activation with dithiothreitol (DTT). In children with concentrations of Pb in whole blood ranging from 0.29 to 1.93 mumol/L, we found the following statistically significant correlations (r): blood Pb vs nonactivated PBGS activity = -0.773 (p less than 0.005); blood Pb vs DTT-activated PBGS activity = -0.265 (p less than 0.005); blood Pb vs the ratio of DTT-activated/nonactivated PBGS activity = +0.818 (p less than 0.005). At a DTT-activated/nonactivated PBGS activity ratio of 1, which indicates no Pb-dependent inhibition of PBGS, a corresponding blood Pb concentration of 0.24 mumol/L (50 micrograms/L) would be predicted. In individuals with hematological disorders, the DTT-activated/nonactivated ratio better predicted blood concentration of Pb than did the nonactivated PBGS activity, and largely compensated for the high variability in PBGS activity. We also describe techniques to minimize contamination by Zn and Pb and to stabilize enzyme activity during collection, transport, storage, and analysis of samples.

Serum aminotransferase activities in sickle cell children during crises

A total of 78 children with diagnosis of sickle cell disease (HbSS) aged 1-12 years were involved in this study; while 60 normal children (HbAA) of the same age range served as controls. Serum levels of alanine aminotransferase (EC 2.6.1.2), aspartate aminotransferase (EC 2.6.1.1), total protein and albumin were assayed in all the sickle cell children both in crises and steady state and in all the normal children. During crises, most of the sickle cell children had significantly raised levels of serum aminotransferases together with reduced levels of serum total protein and albumin. When these levels are compared with the ones observed during the steady state, the differences are highly significant. On the other hand, when the results obtained during the steady state are compared with those of the control group, the differences are not significant. These results are discussed in relation to the hepatic degenerative changes observed in sickle cell crises. It is clear from this study that the more clinical painful crises the children experience, the hepatic cells would be exposed to persistent injury which may eventually result in cell death.

Depressed erythrocyte glutathione reductase activity in sickle cell disease

In a group of 27 sickle cell disease patients ranging in age from 2 yr 3 months to 43 yr, 13 (48%) were found to have depressed erythrocyte glutathione reductase activity suggesting riboflavin deficiency. Glutathione reductase activity coefficients did not correlate with riboflavin intakes which were calculated from 3-day diet records returned by 16 patients. Other causes of riboflavin deficiency including decreased absorption, altered metabolism, or increased excretion of the vitamin must be considered. The potential effect of depressed erythrocyte glutathione reductase activity in the sickle cell disease process is discussed.

Calcium-dependent association of glutathione S-transferase with the human erythrocyte membrane

Elevations in intracellular calcium increase the adsorption of a cytoplasmic protein to human red blood cell membrane. This protein migrates on SDS polyacrylamide gels at 23,000 daltons and has been called band 8. The association of this protein with the membrane is increased in sickle cell anemia. This protein is extracted from the membrane with EGTA, a calcium chelator. Enzymatic and immunological studies identify band 8 as a glutathione S-transferase.

Protein kinases and membrane protein phosphorylation in normal and abnormal human erythrocytes: variation related to mean cell age

Protein kinase activities and membrane autophosphorylation reactions of normal and abnormal human erythrocytes were analyzed. Erythrocytes from patients with high reticulocytosis due to sickle cell anemia and other disorders (n = 13) exhibited elevated activities of total and membrane-bound cAMP-independent casein kinase and cAMP-stimulated histone kinase. Relative to normal controls (n = 10), the average total activities in these abnormal cells were increased 50% and 81%, respectively. The casein and histone kinase activities of normal and abnormal erythrocytes declined significantly with increasing age and buoyant density in Stractan density gradients. Casein kinase activity was highly correlated (r = 0.88; n = 23) with the percentage of reticulocytes in the fraction, consistent with either a progressive loss of activity in mature erythrocytes or an abrupt decline during reticulocyte maturation. The cAMP-independent and cAMP-stimulated autophosphorylation activities of isolated membranes also declined with increasing erythrocyte age. On average, the initial rate of spectrin labeling was 36% lower in ghosts from Stractan gradient bottom fractions, relative to ghosts from top fractions similarly incubated with gamma-32P-ATP. Incorporation into the "band 4.5 zone" (primarily labeling bands 4.8 and 4.9, mol wt 47,800 and 44,600) was also age-dependent. In membranes of unfractionated sickle cells, spectrin autophosphorylation was within normal limits, while 4.5 zone autophosphorylation was increased. Membranes from high reticulocytosis controls (vitamin B-12 deficiency) exhibited similar autophosphorylation patterns, suggesting that the altered autophosphorylation pattern of sickle cell membranes may be attributed to the predominance of very young cells.

Anergy, zinc deficiency, and decreased nucleoside phosphorylase activity in patients with sickle cell anemia

Cell-mediated immunity was evaluated in 26 patients with sickle cell anemia using skin tests for delayed hypersensitivity reactions. Patients with impaired delayed hypersensitivity reactions had lower zinc levels in plasma, erythrocytes, and neutrophils than patients with normal delayed hypersensitivity reactions or controls. The activity of nucleoside phosphorylase, an enzyme essential for T-lymphocyte function, was significantly lower in zinc-deficient patients with anergic sickle cell anemia. We conclude that zinc deficiency in patients with sickle cell anemia is associated with impaired delayed hypersensitivity. Decreased activity of nucleoside phosphorylase may be partially responsible for lymphocyte dysfunction in these patients.

Antioxidant system in sickle red cells

Erythrocytes containing abnormal haemoglobins with high affinity for red cell membrane are subjected to enhanced oxidant stress. Since HbS is known to have high affinity for red cell membrane and sickle cells are particularly susceptible to membrane lipid peroxidation, the behaviour of erythrocyte antioxidant system has been evaluated in 20 subjects, heterozygous for sickle cell anaemia. These subjects have shown normal levels of reduced glutathione, increased superoxide dismutase and glutathione peroxidase activities and low catalase activity. These data suggest that such an unbalanced antioxidant system can not prevent damage by the enhanced production of oxygen free radicals by membrane-bound HbS molecules.

The interaction between (Ca2+ + Mg2+)-ATPase and the soluble activator (calmodulin) in erythrocytes containing haemoglobin S

In normal erythrocytes, a membrane-bound (Ca2+ + Mg2+)-ATPase is stimulated by a soluble activator, calmodulin. Since cells containing Hb S accumulate excessive Ca2+, the defect could lie in either the (Ca2+ + Mg2+)-ATPase or calmodulin. To decide between these two possibilities, we prepared (Ca2+ + Mg2+)-ATPase from erythrocytes of normal (AA), sickle cell trait (AS) and sickle cell disease (SS) individuals. Calmodulin was prepared from haemolysates from AA and SS erythrocytes. The enzyme prepared from SS ghosts had lower specific activity than that from AA membranes. Furthermore, calmodulin from either source did not stimulate the ATPase of SS erythrocytes. Enzyme from AS cells had specific activity similar to that of enzyme prepared from SS membranes. The enzymatic activity of a mixed cell population obtained from an SS patient 8 d following exchange-transfusion was proportional to the per cent Hb A. These results indicate that calmodulin is unable to interact with the enzyme site on the SS membrane. This inability is believed to be due to a specific property of the membrane and not an abnormality of calmodulin itself.

Glutathione peroxidase activity in whole blood of patients with sickle cell anaemia

Whole blood glutathione peroxidase was found significantly increased relative to controls in a group of 21 black patients with sickle cell anaemia. One control group consisted of 15 normal black subjects. A second control group, consisting of 21 black patients with various abnormal haemoglobins including alpha-thalassaemia, also showed a tendency to enhanced glutathione peroxidase activity, confirming previous reports that elevated glutathione peroxidase levels are secondary to a variety of haemolytic conditions, rather than typical of sickle cell anaemia.

Serum alpha-hydroxybutyrate dehydrogenase levels in children with sickle cell disease

Serum alpha-hydroxybutyrate dehydrogenase (alpha-HBDH) levels were determined in 28 children with homozygous sickle cell disease (SCD) during the steady state, crisis, and postcrisis periods. Serum alpha-HBDH levels were also studied in 20 patients with infection. In patients during the steady state, serum alpha-HBDH levels were significantly above control values. During the vaso-occlusive crisis there was a significant further increase in the alpha-HBDH levels. In patients with infection, however, there was no significant increase in serum alpha-HBDH levels. These findings clearly indicate that the level of serum alpha-HBDH in patients with SCD permits differentiation between vaso-occlusive crises, infection, and spurious symptoms.

Human red cell membrane adenylate cyclase in normal subjects and patients with hereditary spherocytosis, sickle cell disease and unidentified hemolytic anemias

We have investigated adenylate cyclase in ghosts from normal and pathologic human red blood cells. Basic parameters such as specific activity, apparent Michaelis constant (KMapp), and response to effectors: sodium fluoride (NaF), 5'-guanylyl imidodiphosphate (Gpp (NH)p), isoproterenol, and PGE1 were investigated. Basal and NaF-stimulated activities were measured in ghosts from patients with hereditary spherocytosis, sickle cell disease, and various unidentified hemolytic anemias. Both activities were increased in any of these pathologic conditions as compared with those of normal red blood cells. Normal values were found in patients with hereditary spherocytosis after splenectomy and in patients with heterozygous sickle cell disease. There was a good correlation between the reticulocyte count and adenylate cyclase activity in hereditary spherocytosis and in sickle cell disease with reticulocyte count lower than 10%. The enzyme activity of the first group was about three times that of the second group. There was no correlation at all in sickle cell disease with higher reticulocytosis and in the group of unidentified hemolytic anemias. These results suggest that increased adenylate cyclase activities are not specific of any of these diseases. In the patients with hereditary spherocytosis, the adenylate cyclase activity seems to be essentially related to younger mean age of red blood cell population while in the patients with sickle cell disease and in others with unidentified hemolytic anemias some additional factors might interfere directly with the enzyme and alter its activity.

Glucose-6-phosphate dehydrogenase deficiency and homozygous sickle cell disease in Jamaica

The relationship between D-glucose-6-phosphate: NADP oxido-reductase (E.C.1.1.1.49; glucose-6-phosphate dehydrogenase; G6PD) deficiency and homozygous sickle cell (SS) disease was examined in 120 patients. The proportions of hemizygotes (22.6%) was slightly more than that observed, and the combined proportions of heterozygotes and homozygotes (28.3%) were slightly less than would be expected, in the general population, but the differences were not significant. However, the proportion of patients of abnormal G6PD status in the 10-19 years age group was 41.7%, significantly more than that found in the 20-29 years age group (0.02 less than P less than 0.05), or expected in the general population (P=0.05). Possible reasons for this are discussed. Difference in G6PD status did not affect the total haemoglobin concentration, reticulocyte count, unconjugated serum bilirubin or Hb F concentration, irreversibly sickled cell counts or plasma haemoglobin concentration, and there was no demonstrable correlation between clinical severity or leg ulceration and abnormal G6PD status.

A new isoenzyme of lactate dehydrogenase associated with sickle cell hemoglobin

Electrophoretic fractionation of lactate dehydrogenase in the cytoplasm of red blood cells containing various types of hemoglobin has revealed a sixth isoenzyme occurring regularly in individuals in whom the major part of the hemoglobin is of the sickle cell type. The newly discovered fraction occurs between the normally present third and fourth components. This discovery marks the first time that an additional lactate dehydrogenase isoenzyme has been found in connection with a clinical abnormality. The isoenzyme may serve as a genetic and clinical marker.

Superoxide dismutase, glutathione peroxidase, catalase and lipid peroxidation of normal and sickled erythrocytes

Sickled erythrocytes showed reduced glutathione peroxidase and catalase activities in comparison to normal erythrocytes. In addition, increased levels of superoxide dismutase and 'peroxidation potential' as well as fluorescent lipid pigments and malonaldehyde suggestive of membrane lipid peroxidation were found in sickled erythrocytes. Finally, sickled erythrocytes showed membrane 'bound' Heinz bodies as well as reduced membrane lipids and unsaturated fatty acids. From these observations, it is suggested that membrane lipid peroxidation occurs in sickled cells.

(Ca2++Mg2+)-ATPase activity of sickle cell membranes: decreased activation by red blood cell cytoplasmic activator

Human red blood cells (RBCs) contain a cytoplasmic protein that activates membrane-bound (Ca2+ + Mg2+)-ATPase and the transport of Ca2+. The (Ca2+ + Mg2+)-ATPase of sickle cells showed a less than normal response to this activator. This was true whether the activator was obtained from normal or sickle cells. Activator present in sickle cell hemolysates fully activated the (Ca2+ + Mg2+)-ATPase of normal RBC membranes. These results demonstrate that membranes of sickle cells are defective in their response to the activator. Neither the apparent affinity for calcium nor the apparent affinity for activator was different comparing the (Ca2+ + Mg2+)-ATPase of sickle and normal membranes. Young, mature, and irreversibly sickled cells were separated by density gradient centrifugation, and membranes were prepared from each of these cell populations. No significant differences in ATPase activities were found based on cell age (density). The (Ca2+ + Mg2+)-ATPase of all populations of sickle cells showed a decreased response to the activator. Thus, it appears unlikely that the decreased response of the (Ca2+ + Mg2+)-ATPase of sickle cells is due to membrane damage caused by repeated sickling during the life-span of the cell. Reduced activation of (Ca2+ + Mg2+)-ATPase by the cytoplasmic activator may account for calcium accumulation in sickle cells.

Membrane components in the red cells of patients with sickle cell anemia. Relationship to cell aging and to irreversibility of sickling

Cholesterol, phospholipid and sialic acid were measured in red cells from patients with sickle cell anemia to determine whether the cells had abnormal concentrations of these components and whether the amounts of these compounds differed in irreversibly sickled cells as compared to non-irreversibly sickled cells. Sickle cells had significantly higher levels of both lipids than similar populations of normal cells, however, comparisons to populations of young control cells showed that the differences were generally not significant. Sialic acid levels in sickle cells were not significantly different from normal cells. Irreversibly sickled cells had lower lipid and sialic acid concentrations than those not irreversibly sickled, but the differences were either not significant or did not occur when compared to young control cells. The studies show that the increased lipid concentrations in the membrane of sickle cells are not abnormal but are related to cell age and that the decrease in membrane components in irreversibly sickled cells is no greater than would be predicted for similarly aged populations of cells.