Normal erythrocyte calpain I activity on membrane proteins under near-physiological conditions in patients with essential hypertension

CONTEXT: It has been reported that the equilibrium between the erythrocyte protease calpain I and its physiological inhibitor calpastatin is disrupted in patients with essential hypertension. OBJECTIVE: To investigate the activity of non-purified calpain I in hemolysates against the erythrocytic membrane proteins, rather than against other substrates. DESIGN: Evaluation of calpain I red cell activity upon its own physiological substrates in hypertensive patients, in a near-physiological environment. SETTING: LIM-23 and LIM-40 of Hospital das Clinicas of the Faculty of Medicine of USP. SAMPLE: Patients with moderate primary hypertension over 21 years of age who were given amlodipine (n:10) and captopril (n:10) for 8 weeks, plus normal controls (n:10). MAIN MEASUREMENTS: Red cell membrane proteins were incubated with and without protease inhibitors and with and without calcium chloride and underwent polyacrylamide gel electrophoresis. RESULTS: Digestion of bands 2.1 and 4.1 was observed, indicating calpain I acitivity. No statistical differences regarding bands 2.1 and 4.1 were observed before treatment, between the controls and the hypertensive patients, either in ghosts prepared without calcium or with increasing concentrations of calcium. Nor were statistical differences observed after treatment, between the controls and the patients treated with amlodipine and captopril, or between the patients before and after treatment with both drugs. CONCLUSION: The final activity of non-purified calpain I upon its own physiological substrate, which was the approach utilized in this study, may more adequately reflect what happens in red cells. Under such conditions no imbalance favoring calpain I activity increase was observed. The protective factor provided by calpastatin against calpain I activity may diminish under hypertension

Membrane Na+ K+ ATPase inhibition related dyslipidemia and insulin resistance in neuropsychiatric disorders.

There are several reports in literature implicating cholesterol metabolism in the pathogenesis of neuronal degenerations, oncogenesis, functional neuropsychiatric disorders and multiple sclerosis. Biosynthesis of cholesterol takes place by the isoprenoid pathway, which also produces digoxin, an inhibitor of membrane Na(+)-K+ ATPase. Inhibition of this enzyme results in intracellular Mg++ deficiency which can influence cholesterol metabolism. Digoxin also influences transport of tryptophan and tyrosine which are precursors of various neurotransmitters. Alterations in digoxin, membrane Na(+)-K+ ATPase and also in neurotransmitters have been reported in the disorders mentioned above. In view of this, serum lipid profile, activity of plasma HMG CoA reductase (the major rate limiting step in the isoprenoid pathway), RBC membrane Na(+)-K+ ATPase activity, serum Mg++ concentration, concentration of digoxin and concentration of serum neurotransmitters were studied in some neuropsychiatric disorders. The serum serotonin level was increased while that of serum dopamine and noradrenaline was reduced. Serum digoxin levels were high and RBC membrane sodium-potasium ATPase activity and serum magnesium were reduced. There was a reduction in HDL cholesterol and increase in plasma triglycerides (pattern similar to insulin resistance and syndrome X) in most of the disorders studied. The HMG CoA reductase activity was high, the serum total cholesterol was increased while RBC membrane cholesterol was reduced in most of the cases. The significance of increased digoxin with consequent inhibition of membrane Na(+)-K+ ATPase in relation to changes in cholesterol metabolism and insulin resistance type of dyslipidemia is discussed in this paper.

Endogenous strychnine, nicotine, and morphine--description of hypo and hyper-strychninergic, nicotinergic and morphinergic state in relation to neuropsychiatric diseases.

Previous work from this laboratory had demonstrated the presence of endogenous morphine, strychnine and nicotine in the mammalian brain and human serum samples. Morphine is synthesised from tyrosine and strychnine and nicotine from tryptophan. This study examines the role of strychnine, nicotine and morphine in neuropsychiatric disorders. The blood levels of tyrosine, tryptophan, strychnine, nicotine and morphine were studied as also RBC membrane Na(+)-K+ ATPase activity. It was found that serum tyrosine levels were reduced and tryptophan levels elevated in all neuropsychiatric disorders studied with a reduction in RBC Na(+)-K+ ATPase activity. Nicotine was present in significant amounts in serum of patients with schizophrenia, CNS glioma and syndrome X with multiple lacunar state. Morphine was present in significant amounts only in the serum of patients with multiple sclerosis and MDP. Strychnine was present in significant amounts in the serum of patients with epilepsy, Parkinson's disease and MDP. The presence of nicotine and strychnine in significant amounts could be related to elevated tryptophan levels suggesting the synthesis of these alkaloids from tryptophan. Morphine was not detected in most of the disorders owing to low tyrosine levels noted in them. Na(+)-K+ ATPase inhibition noticed in most of the disorders could be related to decreased hyperpolarising morphinergic transmission and increased depolarising nicotinergic and strychinergic transmission. The role of morphine, strychnine and nicotine in the pathogenesis of these disorders in the setting of membrane Na(+)-K+ ATPase inhibition is discussed.

Enzymes and membrane proteins of ADSOL-preserved red blood cells

CONTEXT: The preservative solution ADSOL (adenine, dextrose, sorbitol, sodium chloride and mannitol) maintains red cell viability for blood trans-fusion for 6 weeks. It would be useful to know about its preservation qualities over longer periods. OBJECTIVE: To determine some red cell biochemical parameters for peri-ods of up to 14 weeks in order to determine whether the red cell metabo-lism integrity would justify further studies aiming at increasing red cell preservation and viability. DESIGN: Biochemical evaluation designed to study red cell preservation. SETTING: Sao Paulo University erythrocyte metabolism referral center. SAMPLE: Six normal blood donors from the University Hospital of the Universidade Federal do Paranß, Curitiba, Brazil. MAIN MEASUREMENTS: Weekly assay of erythrocyte adenosine-5Ý-triphosphate (ATP), 2,3-diphosphoglycerate (2,3DPG), hexokinase (HX), phosphofructokinase (PFK), pyruvate kinase (PK), glucose-6-phosphate dehydrogenase (G-6-PD), 6-phosphogluconic dehydrogenase (6-PGD), glyceraldehyde-3-phosphate dehydrogenase (GAPD), glutathione reduc-tase (GR), glutathione peroxidase (GSHPx), plasma sodium and potas-sium, blood pH, and membrane proteins of red cells preserved in ADSOL were studied during storage for 14 weeks storage. RESULTS: During ADSOL preservation, erythrocyte ATP concentration decreased 60 percent after 5 weeks, and 90 percent after 10 weeks; the pH fell from 6.8 to 6.4 by the 14th week. 2,3-DPG concentration was stable during the first week, but fell 90 percent after 3 weeks and was exhausted after 5 weeks. By the end of the 5th week, an activity decrease of 16-30 percent for Hx, GAPD, GR, G-6-PD and 6-PGD, 35 percent for PFK and GSHPx, and 45 percent for PK were observed. Thereafter, a uniform 10 percent decay was observed for all enzymes up to the 14th week. The red blood cell membrane pro-teins did not show significant alterations in polyacrylamide gel electro-phoresis (SDS-PAGE) during the 14 weeks. CONCLUSION: Although the blood viability was shown to be poor from the 6th week up to the 14th week of storage due to ATP and 2,3-DPG depletion, the other biochemical parameters remained in fairly good condition for longer storage. As there is a gradual and uniform decay in activity throughout these 14 weeks, it seems that ADSOL-preserved red cells may be used as red cell enzyme standards and membrane proteins as well

Alteraciones en la actividad del calcio-magnesio ATPasa en la membrana de los eritrocitos en pacientes litiasicos con hipercalciuria / Alterations in the calcium-magnesium activity ATPase in the membrane of the erytrosites in lithiasic patients with hypercalciuria

La CaMgATPasa es una enzima involucrada en los movimientos de calcio a través de las membranas biológicas. Nosotros testeamos la actividad de dicha enzima en membranas de eritrocitos de 17 pacientes hipercalciúricos y la comparamos con 8 controles sanos. Los pacientes con hipercalciuria tuvieron una actividad de CaMgATPasa que fue significativamente superior a los controles (18,02 2,83 vs 14,69 1,78 nM . mg-1 p<0,01). La excreción de urinaria de calcio en 24 hs (UCa.V) estuvo directa y significativamente relacionada con la actividad de la enzima (UCa.V: 36,31 x CaMgATPasa - 371,08 r:0,65 p<0,05) sólo en pacientes con hipercalciuria. Cuando agrupamos los pacientes acorde al diagnóstico fisiopatológico en hipercalciuria absortiva (HCA) e hipercalciuria renal (HCRT) encontramos que la actividad enzimática estuvo sólo significativamente elevada en aquellos portadores de HCA al compararlos con los controles (19,17 3,49 vs 14,68 1,79 nM . mg-1 .min-1 p<0,025).No encontramos diferencias estadísticamente significativas entre HCRT y controles (16,83 1,99nM . mg-1 . min-1; p:NS) y en HCRT vs HCA (p<0,14). Concluimos que las alteraciones en el transporte de calcio en la hipercalciuria dependería de anormalidades en la actividad de la CaMgATPasa

Ca(2+)-induced alterations in the activity of membrane (Ca(2+)-Mg2+)-ATPase of human and rat erythrocytes.

Effect of intraerythrocyte Ca2+ elevation on human and rat erythrocyte membrane (Ca(2+)-Mg2+)-ATPase along with that of incubation of the erythrocyte ghosts in their own hemolysates enriched with Ca2+ has been studied. While the membrane (Ca(2+)-Mg2+)-ATPase levels of Ca(2+)-loaded human erythrocytes showed an initial increase and subsequent decline, membranes incubated in their own hemolysate showed a consistent decrease in the enzyme activity. Calmodulin sensitivity was retained by the preparations in contrast to the earlier observations made with washed erythrocyte membranes. Similar changes in (Ca(2+)-Mg2+)-ATPase activity but of greater magnitude were observed in response to Ca2+ in the calpain-rich rat erythrocytes. Considerable crosslinking and proteolysis was observed in case of human and rat erythrocytes exposed to high Ca2+ concentrations. The Ca(2+)-activable transglutaminase, however, did not play any role in the activation of the (Ca(2+)-Mg2+)-ATPase.

Intracellular calcium homeostasis in Leishmania mexicana. Identification and characterization of a plasma membrane calmodulin-dependent Ca(2+)-ATPase

The intracellular Ca2+ concentration in different trypanosomatids is about 50 nanomolar, which concentration in different trypanosomatids is about 50 nanomolar, which is 4 orders of magnitude lower than in the extracellular milieu. This fact implies the existence of well developed mechanisms for the maintenance of such a high calcium gradient. In higher eukaryotics a number of different structures have been implicated in this function. Some of them are located in intracellular organelles, and others in the plasma membrane. Since intracellular organelles are limited by their storage capacity, long-term Ca2+ homeostasis resides solely in the plasma membrane. In higher eukaryotics, a calcium pump or Ca(2+)-ATPase located in the plasma membrane, because of its high Ca2+ affinity, has been proposed as the structure responsible for the maintenance of the cytoplasmic Ca2+ concentration at the submicromolar level. The presence of a Ca(2+)-ATPase in trypanosomatids has been debated. While some groups have reported its absence, others have reported the existence of an enzyme which is Mg(2+)-independent or even inhibited by Mg2+. On the other hand, in none of these reports any correlation was shown between the Ca(2+)-ATPase activity observed and the Ca2+ transport function attributed to this enzyme. We have previously shown that a calmodulin-stimulated Mg(2+)-dependent Ca(2+)-ATPase is present in the plasma membrane of Leishmania braziliensis and of Trypanosoma cruzi. Plasma membrane vesicles from these parasites are able to accumulate Ca2+ in the presence of the ATP-Mg complex. The similarities found between the kinetics parameters and other properties of the Ca(2+)-ATPase and the Ca2+ transport activity strongly suggest a common molecular entity. The stoichiometry calculated from these parameters approaches the 1:1 stoichiometry for Ca2+ and ATP, as reported for the Ca2+ pump from higher eukaryotic cells. In this report we show that plasma membrane vesicles from Leishmania mexicana possess a Ca(2+)-ATPase with characteristics which are similar to that reported by us for other trypanosomatids. Thus, the enzyme has a high Ca2+ affinity which is further increased upon addition of calmodulin. The maximal velocity is also increased by calmodulin...

Abnormal erythrocyte Na, K-ATPase activity in a northeastern Thai population.

We studied the cellular membrane enzyme responsible for potassium transport in different Thai populations. We measured plasma and intraerythrocytic concentrations of sodium and potassium, activities of erythrocytic membrane Na, K-activated adenosine triphosphatase (Na, K-ATPase), ouabain-insensitive ATPase, total ATPase and the activity ratio of Na, K-ATPase/total ATPase in 25 healthy blood donors at Khon Kaen University Hospital, Khon Kaen (group 1), and in 32 donors at the National Blood Center, Thai Red Cross Society, Bangkok (group 2). Group 1 subjects had significantly higher concentrations of erythrocyte sodium (p < 0.001) and lower activity of Na, K-ATPase (p < 0.001) than group 2. When data of these 2 groups were combined, erythrocyte Na+ correlated inversely with Na, K-ATPase and the activity ratio of Na, K-ATPase/total ATPase. Our study suggests that there is a defect in membrane transport enzymes for sodium/potassium in certain northeast Thai populations.

Membrane-associated protease activity of human erythrocytes.

Membrane-associated protease activity capable of digesting a number of membrane cytoskeletal proteins including band 3 protein was identified in human erythrocytes, almost totally free from contaminating leucocytes and platelets. This enzyme was inhibited by aprotinin (a specific inhibitor for a class of serine protease) and was distinct from the cytosolic calcium-dependent thiol protease (calpain), which is also known to bind to red cell membrane.

Regulation of red cell acetylcholinesterase activity in diabetes mellitus.

Despite the fact that the significance of red cell membrane acetylcholinesterase (AChE) is unknown, this enzyme of red cell assumes importance since many of its properties have been found to be similar to purified enzyme form of brain tissues. Our investigations on the effect of insulin-dependent diabetes mellitus on red cell AChE revealed that the activity of this enzyme is significantly decreased in diabetes. Insulin treatment restored the activity to the normal level. Solubilization of normal, diabetic and insulin treated diabetic red cell membranes with Triton X-100 (0.2% v/v) caused a general decline in AChE activity, however the per cent decline in activity of diabetic enzyme was lower as compared to normal and insulin treated conditions. From our results it is inferred that the decreased red cell AChE activity in diabetes is due to lesser number of active enzyme molecules and also due to altered membrane microenvironment.

Tannic acid as a marker for membrane sidedness of human red cell vesicles

Membrane sidedness of human eythrocytes was investigated in inside-out vesicles (IOV's), ghosts and intact cells by means of transmission electron microscopy (e.m.) after tannic acid fixation. No gross difference in appeearance of either membrane surface was observed when IOV's were subjected to conventional e.m. preparation. This included in addition to tannic acid, a double fixation with glutaraldehyde and osmium, followed by "en bloc" and thin section staining with uranyl acetate and lead citrate. By contrast, if IOV's were treated with a high EDTA concentration (2-5 mM) before tannic fixation, granular, electron-dense deposits were found on one of the surfaces. The presence of such a meterial was unaffected by neuraminidase treatment prior to the EDTA step. On the hand, red cells show no electron-dense deposits when exposed to EDTA (5 mM) unless they presented a light cytoplasm and an altered membrane appearance. Such a material was only observed on the inner membrane surface. Furthermore, a similar distribution of such deposits following EDTA treatment was also found in white ghosts before being induced to vesiculate. These results indicate that tannic acid can be employed as a marker for the cytoplasmic surface of the human erythrocyte membrane when used in combination with EDTA