Suppressive effect of culture supernatant of erythrocytes and serum from dogs infected with Babesia gibsoni on the morphological maturation of canine reticulocytes in vitro

The present study evaluated the effects of infected culture supernatant of erythrocytes, fractionation of culture supernatant and serum from dogs infected with Babesia gibsoni (B. gibsoni) on the maturation of canine reticulocytes in vitro. The SDS-PAGE demonstrated that significantly broader bands were generated by both the infected culture supernatant of erythrocytes and the serum from dogs chronically infected with B. gibsoni. The culture supernatant of erythrocytes infected with B. gibsoni strongly suppressed the maturation of reticulocytes. Prior studies showed that chronically infected serum had inhibitory effects on both the maturation of reticulocytes and the canine pyrimidine 5'-nucleotidase subclass I and purine-specific 5'-nucleotidase activity. In addition, serum free infected culture supernatant of erythrocytes had an inhibitory effect on the morphological maturation of reticulocytes. These results suggest that infected serum and culture supernatant of erythrocytes might accumulate excess proteins and/or metabolites as a result of the inhibited maturation of reticulocytes and decreased activity of erythrocyte 5'-nucleotidase. Furthermore, the fractions observed at >150 kDa- and 150-70 kDa- in the infected culture supernatant and serum retarded the maturation of canine reticulocytes in vitro. The results obtained from the in vitro examinations, in the present study, suggested that B. gibsoni itself and/or its metabolites might release certain proteins in the infected culture supernatant and serum from infected dogs and as a result delay morphological maturation of canine reticulocytes

(Na,K)-ATPase and Ouabain binding in reticulocytes from dogs with high K and low K erythrocytes and their changes during maturation.

The present study demonstrated that dog reticulocytes had considerable amounts of (Na,K)-ATPase, but lost it rapidly during maturation into erythrocytes. Furthermore, reticulocytes from dogs possessing erythrocytes characterized with high (Na,K)-ATPase activity and high K, low Na concentrations (HK dogs; Maede, Y., Inaba, M., and Taniguchi, N. (1983) Blood 61,493-499) had more ouabain binding sites than cells from normal dogs (LK dogs). Our results were as follows: i) The maximal binding capacities (Bmax) for ouabain binding at equilibrium were approximately 0 and 1,500 binding sites/cell in LK and HK dog erythrocytes, respectively. ii) Reticulocytes from LK dogs possess approximately 5,700 ouabain binding sites/cell. iii) The Bmax value for ouabain in HK reticulocytes was about 10,000 sites/cell, being 2-fold that in LK reticulocytes. iv) Ouabain-sensitive fluxes of 24Na and 42K in each type of reticulocyte were compatible with the number of ouabain binding sites on the cells. v) Ouabain binding capacity, as well as (Na,K)-ATPase activity, in the reticulocytes from LK dogs fell rapidly to nearly zero during the maturation into erythrocytes. vi) Although reticulocytes from HK dogs also showed a similar regression of (Na,K)-ATPase during maturation, they retained a certain number of ouabain binding sites even after maturation, resulting in the high activity of (Na,K)-ATPase in HK erythrocyte membrane

Increase of Na+ gradient-dependent L-glutamate and L-aspartate transport in high K+ dog erythrocytes associated with high activity of (Na+, K+)-ATPase.

As reported previously, some dogs possess red cells characterized by low Na+, high K+ concentrations, and high activity of (Na+, K+)-ATPase, although normal dog red cells contain low K+, high Na+, and lack (Na+, K+)-ATPase. Furthermore, these red cells show increased activities of L-glutamate and L-aspartate transport, resulting in high accumulations of such amino acids in their cells. The present study demonstrated: (i) Na+ gradient-dependent L-glutamate and L-aspartate transport in the high K+ and low K+ red cells were dominated by a saturable component obeying Michaelis-Menten kinetics. Although no difference of the Km values was observed between the high K+ and low K+ cells, the Vmax values for both amino acids' transport in the high K+ cells were about three times those of low ones. (ii) L- and D-aspartate, but not D-glutamate, competitively inhibited L-glutamate transport in both types of the cells. (iii) Ouabain decreased the uptake of the amino acids in the high K+ dog red cells, whereas it was not effective on those in the low K+ cells. (iv) The ATP-treated high K+ cells [(K+]i not equal to [K+]o, [Na+]i greater than [Na+]o) showed a marked decrease of both amino acids' uptake rate, which was almost the same as that of the low K+ cells. (v) Valinomycin stimulated the amino acids' transport in both of the high K+ and the ATP-treated low K+ cells [( K+]i greater than [K+]o, [Na+]o), suggesting that the transport system of L-glutamate and L-aspartate in both types of the cells might be electrogenic. These results indicate that the increased transport activity in the high K+ dog red cells was a secondary consequence of the Na+ concentration gradient created by (Na+, K+)-ATPase

Na,K-ATPase in dog red cells. Immunological identification and maturation-associated degradation by the proteolytic system.

The Na,K-ATPase of red cells from high K+ and low K+ dogs was studied immunologically by using antibodies raised against dog kidney enzyme. Anti-alpha subunit IgGs, which also recognized alpha (+) from brain enzyme, identified the larger subunit of erythrocyte Na,K-ATPase as a homogeneous polypeptide with Mr = 96,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by immunoblotting. In addition, erythrocyte Na,K-ATPase, purified by immunoaffinity chromatography on a monoclonal antibody-coupled column, showed the identity of its polypeptide composition to that of the renal enzyme. Furthermore, it was shown that reticulocyte lysates from high K+ and low K+ dogs substantially degraded 125I-Bolton-Hunter reagent-labeled Na,K-ATPase. This degradation of the enzyme protein was significantly enhanced by the addition of ATP and Mg2+. These results indicate that dog reticulocytes possess some mechanism for protein breakdown involving an ATP-dependent proteolytic system, resulting in the dramatic breakdown of Na,K-ATPase activity during dog reticulocyte maturation into erythrocytes (Maede, Y., and Inaba, M. (1985) J. Biol. Chem. 260, 3337-3343)

A CASE OF MEGALOBLASTIC ANEMIA IN THE GIBBON (HYLOBATES FOOLOCK)

An adult female gibbon kept in a zoo for six years was affected with a disease showing diarrhea and anemia. Blood examinations revealed that she was diseased by the macrocytic megaloblastic anemia associated with a marked left shift in neutrophils. Nuclei of the neutrophils were large and bizarre, and Dohle bodies and toxic granules were observed in the cytoplasm. By the treatment with vitamin B_ injection for two days, the megaloblasts in peripheral blood disappeared and instead normoblasts increased. Autopsy findings showed no significant gross changes, however histopathologically, focal edematous induration in the liver and subacute catarrhal enterocolitis were markedly noticed

Increase of Na-K-ATPase activity, glutamate, and aspartate uptake in dog erythrocytes associated with hereditary high accumulation of GSH, glutamate, glutamine, and aspartate.

We have found convincing evidence for the presence of Na-K-ATPase and high potassium (K) and low sodium (Na) concentrations in the erythrocytes of some dogs associated with hereditary high concentrations of erythrocyte glutathione and some amino acids, glutamate, glutamine, and aspartate. The Na-K-ATPase activity of the erythrocyte membranes of the dogs was about 3 times that of human erythrocyte membranes, whereas the enzyme activity was not detected in control dogs with a normal level of blood glutathione. The Michaelis constant of the enzyme for ATP (Km ATP) was 6.6 X 10(-3)M in the dogs' erythrocytes and 5.0 X 10(-4)M in the human erythrocytes. The concentration of K in the erythrocytes in the dogs examined was about 11 times that of the controls, whereas the erythrocyte Na concentration in the dogs was about one-third that of the controls. The concentrations of K and Na in the plasma of the dogs were equal to those of the controls. Furthermore, L-3H-glutamate and L-3H-aspartate uptake by those cells with high activity of Na-K-ATPase greatly increased, while L-3H-glutamine uptake was unchanged. It appeared that Na+ and K+ gradients created by Na-K-ATPase across the cell membrane might stimulate glutamate and aspartate uptake by the cells, thus causing the high accumulation of such amino acids in the cells

MITOGENIC RESPONSIBILITIES OF LYMPHOCYTES IN CANINE BABESIOSIS AND THE EFFECTS OF SPLENECTOMY ON IT

In order to clarify the mechanisms of immune-responses in canine babesiosis, mitogen-induced transformation of lymphocytes from peripheral blood and its relation to parasitemia were chiefly examined in both intact and splenectomized dogs suffering from Babesia gibsoni. The lymphocyte responses to PHA-P, Con A and PWM in dogs infected with B. gibsoni were all extremely depressed as the parasite increased in their peripheral blood. The lymphocyte responses to the mitogens greatly decreased after splenectomy in both groups infected and noninfected with B. gibsoni. Furthermore, severe relapse of parasitemia appeared in the infected dogs after splenectomy. Mild parasitemia and moderate anemia were prolonged for at least 3 months with a high serum IFA titer to the parasite in splenectomized dogs

Hereditary high concentration of glutathione in canine erythrocytes associated with high accumulation of glutamate, glutamine, and aspartate

We have found a dog family in which there were five cases of increased red cell glutathione corresponding to four to five times the normal concentration without any clinical signs. In the present study, we mainly examined the concentrations of free amino acids in the erythrocytes, plasma, and urine of two of the dogs, and we demonstrated that the concentrations of glutamate, aspartate, and glutamine in their erythrocytes increases to 92, 63, and 13 times the mean value in the normal blood, respectively. There were no changes observed in the other amino acids as compared to normal, although the glycine and histidine in the erythrocyte showed slight increases. The concentrations of amino acids in the plasma and urine of the dogs were almost equal to normal ones. The activities of some of the enzymes involved in the glutathione metabolism in the erythrocytes from the two dogs were all within the normal range. The increased level of glutathione could be explained by the fact that the feedback inhibition of gamma-glutamyl cysteine synthetase by glutathione was released by the high levels of glutamate in the erythrocytes

THE RELATIONSHIP BETWEEN REDUCED GLUTATHIONE LEVEL AND GLUTATHIONE S-TRANSFERASE ACTIVITY IN SHEEP ERYTHROCYTES

The relationship between reduced glutathione (GSH) level and glutathione S-transferase (GST) activity in erythrocytes was examined, using sheep erythrocytes, which have varying GSH concentrations, and dog erythrocytes with an inherited high concentration of GSH. There was a positive correlation (r=0.529,p<0.001) between the GSH level and GST activity in sheep erythrocytes. In dog erythrocytes, the GST activity in high-GSH cells was significantly (p<0.001) higher than that in normal-GSH cells. These results indicate that the activity of GST in erythrocytes is directly correlated with the intracellular GSH level