An improved procedure for the preparation and measurement of (Na+ + K+)-ATPase in human erythrocytes

Changes in erythrocyte membrane ATPases and plasma lipid peroxides in upper abdominal surgery under intravenous procaine-balanced anesthesia

AIM: To observe the changes in erythrocyte membrane ATPases and plasma lipid peroxides (LPO) patients with in abdominal surgery under intravenous procaine balanced anesthesia.

METHODS: By determining the ATPase activities of erythrocyte membrane, effects of upper abdominal surgery under intravenous procaine-balanced anesthesia on the function of erythrocytes were observed in 15 patients undergoing cholecystectomy and gastrectomy (5 males and 10 females, aged 45.9 ± 10.20 years and weighed 60.60 kg ± 11.93 kg). All patients were free from severe renal,hepatic, pulmonary, cardiac, metabolic and endocrinological diseases and acute infection for at least 2 weeks before surgery. Patients receiving any drug known to affect carbohydrate metabolism prior to anesthesia were excluded from the study.

RESULTS: Erythrocyte membrane Na⁺, K⁺-ATPase, Mg²⁺-ATPase, Ca²⁺, Mg²⁺-ATPase activities were not significantly changed 60 min-90 min after incision as compared with 30min before anesthesia, but were decreased markedly 10min and 24 h after completion of operation (P ＜ 0.01). Plasma lipid peroxides (LPO) were increased significantly 24 h after surgery (P ＜ 0.01) following an initially marked but transient reduction. Plasma LPO changes were not correlated with erythrocyte membrane ATPase activities, r = -0.0396, -0.0097 and 0.4383, respectively (P ＞ 0.05).

CONCLUSION: Abdominal surgical trauma under intravenous procaine-balanced anesthesia may be associated with the decreased ATPase activities of erythrocyte membrane and increased LPO in plasma.

Low erythrocyte Na/K-pump activity and number in northeast Thailand adults: evidence suggesting an acquired disorder

Healthy northeastern Thais have a higher erythrocyte sodium concentration and a lower erythrocyte membrane Na,K-adenosine triphosphatase (ATPase) activity than central Thais. To elucidate whether the defect is hereditary or acquired, we studied plasma sodium and potassium and erythrocyte sodium, potassium, Na,K-ATPase activity, and ouabain-binding sites (OBS) in the following groups: healthy newborns of ethnic central Thais (group 1), healthy newborns of ethnic northeast Thais (group 2), healthy adults of central Thailand ethnicity who lived in the rural central region (group 3) or in Bangkok (group 4), healthy adults of northeast Thailand ethnicity who lived in the rural northeast region (group 5) or who migrated to work in Bangkok for at least 1 year (group 6). Erythrocyte Na was higher in group 2 than in group 1. Group 3 had lower erythrocyte Na,K-ATPase activity than group 4, and it was lower in group 5 than in group 6. Among all groups, group 5 had the highest erythrocyte Na (11.6 mmol/L,F < 0.0001) and the lowest Na,K-ATPase activity (63 mmol Pi/mg x h, F < 0.0001) and erythrocyte OBS (397 sites per cell, F < 0.05) than the other adult groups. There was a positive correlation between erythrocyte Na,K-ATPase and erythrocyte OBS (r = .416, P < .0001). Multiple regression analysis demonstrated a correlation between erythrocyte Na as a dependent variable and erythrocyte OBS, plasma potassium, erythrocyte potassium, and erythrocyte Na,K-ATPase (r = .517, P < .0001). The erythrocyte Na,K-ATPase/OBS ratio, an expression of Na,K-ATPase activity equalized for the number of Na,K-pump units, was lowest among rural adults of the central region (group 3) and the northeast region (group 5) (F < 0.0002). Our data suggest that rural dwellers in Thailand tend to have lower erythrocyte Na,K-ATPase activity than urban dwellers and that this is probably acquired after birth. It was more severe among those from the northeast versus the central region, and was less severe among those who migrated to an urban area. This defect in northeast rural dwellers was probably associated with low numbers of Na,K-pump units and a defect of the pump to express activity, whereas in central rural dwellers it was probably associated with the latter condition. We postulate that there might be circulating Na,K-pump inhibitors and metabolic disturbances that cause attenuation of Na,K-ATPase function and synthesis in the northeast Thailand rural population, and that such substances may have an environmental origin. There may be a relationship between these abnormalities and sudden unexpected deaths.

Inhibitin: a specific inhibitor of sodium/sodium exchange in erythrocytes

An inhibitor of ouabain-insensitive sodium/sodium exchange in erythrocytes has been isolated from leukemic promyelocytes. To explore the specific effects of this inhibitor, named inhibitin, sodium transport experiments were carried out in human erythrocytes. Inhibitin reduced ouabain-insensitive bidirectional sodium transport. It did not change net sodium fluxes, had no significant effect on rubidium influx, and did not inhibit sodium-potassium-ATPase activity. The inhibitory effect of inhibitin was studied on sodium/sodium exchange and on sodium/lithium countertransport in 140 mM sodium and in sodium-free media. In the presence of sodium, inhibitin reduced sodium and lithium efflux to that observed in sodium-free medium. Inhibitin showed no reduction in sodium or lithium efflux when sodium was replaced by choline chloride or Mg2+. When inhibitin was combined with one or more of the other transport inhibitors (i.e., ouabain, furosemide, or bumetanide and amiloride), its inhibitable component remained distinct and it did not overlap with that of the other inhibitors. These studies show that inhibitin is a specific inhibitor of carrier-mediated sodium/sodium exchange and sodium/lithium countertransport processes in human erythrocytes.

Elevated skeletal muscle sodium-potassium-ATPase in human obesity

To determine whether muscle sodium-potassium-ATPase activity, an expression of energy turnover, is increased in obesity, we studied a group of nine non-obese and seven obese subjects undergoing elective cholecystectomy. The muscle ATPase activity was 87 per cent higher (p less than 0.001) in obese subjects compared with non-obese subjects. The increase in the ATPase activity positively correlated with both the body mass index (r = 0.81) and excess body weight (r = 0.75). No relationship was found between erythrocyte and muscle sodium-potassium-ATPase activities (r = 0.25). These findings demonstrate an increased ATPase activity in skeletal muscle obtained from obese subjects and that the erythrocyte is an inaccurate marker of this enzyme with respect to other body tissue.

Erythrocyte sodium pump activity in human obesity

In an attempt to resolve the prevailing confusion about erythrocyte sodium pump activity in obesity, we measured sodium-potassium-ATPase, ouabain-inhibitable (active) sodium efflux rate constant and intracellular sodium concentration in erythrocytes from 107 non-obese and obese subjects, with a body-mass index ranging from 17 to 54 kg X m-2. All the three independently measured variables were not significantly different between the two groups and no correlations were found between these three indices and body-mass index. The expression of ATPase activity in units of membrane protein allowed our previous data to be compared with this study and other reports. Our studies and most of the published reports suggest that there is no difference in erythrocyte sodium-potassium-ATPase and sodium transport between the vast majority of obese and non-obese subjects, but there is a subgroup of obese subjects (about 5%) with abnormally high erythrocyte sodium pump activity. The variable treatment of data from this subgroup and the small numbers of obese subjects studied by various investigators are largely responsible for the conflicting results about erythrocyte sodium pump activity.