Erythrocytes may contain a ouabain-insensitive K+-ATPase which plays a role in internal K+ balance
Braz. j. med. biol. res
;
36(12): 1769-1772, Dec. 2003. ilus, tab
Artículo
en Inglés
| LILACS
| ID: lil-350467
RESUMO
Erythrocytes are useful in evaluating K+ transport pathways involved in internal K+ balance. Several forms of H+,K+-ATPase have been described in nephron segments active in K+ transport. Furthermore, the activity of a ouabain-insensitive isoform of H+,K+-ATPase expressed in collecting duct cells may be modulated by acid-base status. Various assays were performed to determine if a ouabain-insensitive K+-ATPase is present in rat erythrocytes and, if so, whether it plays a role in internal K+ balance. Kinetic studies demonstrated that maximal stimulation of enzyme activity was achieved with 2.5 mM K+ at pH 7.4. Subsequent experiments were performed on erythrocyte membranes collected from animals submitted to varying degrees of K+ homeostasis control rats, K+-depleted rats, K+-loaded rats, and rats rendered hyperkalemic due to acute renal failure. As observed in the collecting duct cell studies, there was a significant decrease in the activity of ouabain-insensitive K+-ATPase in the erythrocytes of both K+-loaded and metabolically alkalotic K+-depleted rats. However, this enzyme activity in erythrocyte membranes of rats with metabolic acidosis-related hyperkalemia was similar to that of control animals. This finding may be interpreted as resulting from two potentially modulating factors the stimulating effect that metabolic acidosis has on K+-ATPase and the counteracting effect that hyperkalemia and uremia have on metabolic acidosis. In summary, we present evidence of a ouabain-insensitive K+-ATPase in erythrocytes, whose activity is modulated by acid-base status and K+ levels.
Texto completo:
Disponible
Índice:
LILACS (Américas)
Asunto principal:
Ouabaína
/
Potasio
/
ATPasa Intercambiadora de Hidrógeno-Potásio
/
Eritrocitos
Límite:
Animales
Idioma:
Inglés
Revista:
Braz. j. med. biol. res
Asunto de la revista:
Biologia
/
Medicina
Año:
2003
Tipo del documento:
Artículo
/
Congreso y conferencia
/
Documento de proyecto
País de afiliación:
Brasil
Institución/País de afiliación:
Universidade de São Paulo/BR
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