Increased calcium uptake in the red cells of unsplenectomized patients with hereditary spherocytosis: significant contribution of reticulocytosis.

The presence of abnormal calcium (Ca) metabolism in the red cells of hereditary spherocytosis (HS) patients has long been in dispute. Thus, to clarify the discrepancies of experimental results published previously, Ca metabolism in the red cells was investigated in 12 unsplenectomized and 6 splenectomized HS patients. A marked increase of Ca uptake was observed in the ATP-depleted red cells of the unsplenectomized HS patients. The increased red cell Ca uptake was normalized after splenectomy in the same HS patients. The extent of increased Ca uptake was well correlated to the degree of reticulocytosis (p less than 0.001). The observation was confirmed by the fractionation studies of the HS red cells. Ca uptake was not increased in the spherocyte-rich bottom fraction, if reticulocytosis was not present. No significant difference was observed in red cell calcium content between normal and HS patients, neither unsplenectomized nor splenectomized.

Disappearance of microspherocytes in peripheral circulation and normalization of decreased lipids in plasma and in red cells of patients with hereditary spherocytosis after splenectomy.

A possible mechanism of the formation of microspherocytosis in unsplenectomized patients with hereditary spherocytosis (HS) was investigated in relation to lipid metabolism in plasma and in red cells of these patients. Plasma lipids (total cholesterol, free cholesterol, high density lipoprotein cholesterol, free fatty acids, and phospholipids) were markedly reduced in unsplenectomized HS patients with microspherocytosis. Red cell membrane lipids (free cholesterol and phospholipids such as phosphatidyl ethanolamine, sphingomyelin, phosphatidyl choline, and lysophosphatidyl choline) were also decreased in these unsplenectomized HS patients. After splenectomy, microspherocytosis disappeared concomitant to substantial normalization of plasma and red cell membrane lipids. These observations suggest that plasma lipid decrement in the unsplenectomized HS patients is at least one of the causative factors in pathogenesis of the formation of microspherocytosis. So-called "splenic conditioning" may not imply a physical "loss" of membrane by fragmentation or pitting of the once-formed HS red cells in the peripheral circulation. Instead, the decreased plasma lipids in the presence of the spleen may affect the de novo synthesis of red cell membrane lipids, resulting in the formation of microspherocytosis.

Decreased sodium influx and abnormal red cell membrane lipids in a patient with familial plasma lecithin: cholesterol acyltransferase deficiency.

Red cell membrane metabolism in familial lecithin:cholesterol acyltransferase (LCAT) deficiency was investigated. The family presented here is the third case discovered in Japan. An increase of free cholesterol was observed in the red cell membranes, concomitant with increased phosphatidyl choline. Osmotic fragility of the patient's red cells was diminished rather than increased. Red cell survival (51Cr T1/2) was shortened (15 days). Sodium influx was markedly decreased, although sodium efflux, both ouabain-sensitive and ouabain-insensitive, was normal. The activity of acetyl-cholinesterase as a marker of the outer leaflet of the red cell membranes was decreased, while the activity of glyceraldehyde-3-phosphate dehydrogenase as a marker of the inner leaflet was normal. No abnormalities of adenosine triphosphatases in red cell membranes were observed. These results suggest that the alteration of cholesterol metabolism in the plasma of LCAT deficiency increases the red cell membrane cholesterol and affects the functions of the red cell membranes, especially of the outer leaflet, which may result in decreased sodium influx.

Self-adaptive modification of red-cell membrane lipids in lecithin: cholesterol acyltransferase deficiency. Lipid analysis and spin labeling.

In a patient with lecithin: cholesterol acyltransferase deficiency, free cholesterol was markedly increased, and esterified cholesterol was diminished. In the patient's plasma, an increase in phosphatidylcholine (PC) and a decrease in sphingomyelin were observed. Concomitantly, an increase in a shorter acyl chain 16:0 was noted in PC, sphingomyelin and phosphatidylethanolamine (PE). In contrast to these results, longer chains such as 22:0 and 24:0 were decreased, especially in sphingomyelin. Unsaturated double bonds such as 18:1 was also increased in PC and PE. In the red-cell membrane lipids, the increase in free cholesterol was counteracted by an increase in PC and by a decrease in sphingomyelin and PE, reflecting changes in the patient's plasma lipids. Increased 16:0 (in PC) and decreased 18:0 and 24:0 were observed. The increased plasma free cholesterol due to metabolic defect (lecithin: cholesterol acyltransferase deficiency) led to decreased red-cell membrane fluidity. This effect appeared to be counteracted by changing phospholipid composition (increased PC and decreased sphingomyelin and PE), by increasing shorter chains (16:0), by decreasing longer chains (18:0 and 24:0) and by increasing unsaturated double bonds (18:2). These results can be interpreted as a self-adaptive modification of lecithin: cholesterol acyltransferase deficiency-induced red-cell membrane abnormalities, to maintain normal membrane fluidity. This speculation was supported by the ESR spin-label studies on the patient's membrane lipids. The normal order parameters in intact red cells and in total lipid liposomes were decreased if cholesterol-depleted membrane liposomes were prepared. Thus, the hardening effect of cholesterol appeared to be counteracted by the softening effects described above. Overall membrane fluidity in intact red cells of the lecithin: cholesterol acyltransferase-deficient patient was maintained normally, judged by order parameters in ESR spin-label studies.

Membrane protein phosphorylation and protein kinases in normal and hereditary spherocytosis red cells.

Membrane protein phosphorylation by protein kinases in normal red cells takes place mainly on band 2 at the basal activity, and on bands 1 and 2.1 in the presence of cyclic 3':5'-adenosine monophosphate. Calcium precipitates preferentially bands 1 and 2.1 on extracted membrane proteins, and inhibit the membrane protein phosphorylation. Phosphorylation of endogeneous membrane proteins is diminished in red cells of some patients with hereditary spherocytosis (HS), partly corresponding reciprocally to MCHC, % spherocytes and reticulocytosis in peripheral blood of these patients, although the enzymatic activities of glyceraldehyde-3-phosphate dehydrogenase as a marker of the inner surface of red cell membranes are maintained normally in these red cells. The pattern of membrane protein fractions in HS red cells as endogeneous substrates for phosphorylation reactions is almost identical to that in normal red cells. Activities to phosphorylate casein or histone as exogeneous substrates are normal in HS red cell ghosts.