Modulation of Na, K-ATPase activity by immunoglobulins--1. Effects of IgM on the Na, K-ATPase activity in glomerulonephritis.
BACKGROUND
In the cases of acute glomerulonephritis unfavourable outcome is related to increased blood concentration of IgM. We assumed that pathologic changes in glomerulonephritis might result from direct binding of IgM antibodies to Na, K-ATPase in the nephron channels.


METHODS
The study involved 30 patients suffering from glomerulonephritis. Na, K-ATPase activity was studied in the erythrocytes of these patients and healthy controls at different concentrations of Mg2+ ions in the incubation media.


RESULTS
Na, K-ATPase activity in the erythrocytes of healthy subjects was shown to gradually diminish at the increasing concentrations of Mg2+ ions. Another pattern was displayed for the enzyme activity in glomerulonephritis patients--a sharp decrease of the enzymatic activity at 6 mM Mg2+, as compared with that at 3 mM, and restoration to essentially the starting level at 12 mM. Incubation of erythrocytes from healthy subjects with plasma from glomerulonephritis patients changed the response of Na, K-ATPase activity to Mg2+ concentration to that typical for glomerulonephritis patients. Analogous changes were caused by adding IgM antibodies to whole blood. It was demonstrated in vivo, that hypotonic artificial mineralised water "Marina" restores Na, K-ATPase activity in erythrocytes of glomerulonephritis patients and reduces proteinuria.


CONCLUSIONS
We have postulated, that the changes in the Na, K-ATPase activity, typical for glomerulonephritis patients are caused by the interaction of the enzyme with immunoglobulin M antibodies. The lack of difference between the Na, K-ATPase activity in erythrocyte ghosts from healthy subjects and glomerulonephritis patients suggests that the immunoglobulin M attachment site is on the outer membrane and that the toxic factor could be removed.
Ponomarenko
E
E
Latvian Academy of Medicine, Riga. jelena_p99@yahoo.com
Pletneva
T
T
Kalvins
I
I
D000328:Adult; D004912:Erythrocytes / Q000201:enzymology; D005260:Female; D005921:Glomerulonephritis / Q000097:blood / Q000201:enzymology*; D006801:Humans; D007075:Immunoglobulin M / Q000502:physiology*; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D007075:Immunoglobulin M; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium