Erythrocytes may contain a ouabain-insensitive K+-ATPase which plays a role in internal K+ balance

Autor(es)

L.F.B.C. Seguro ^[1] ; D.L.B.C. Seguro ^[2] ; C.M.B. Helou ^[3]

Afiliação do(s) autor(es)

^[1] Universidade de São Paulo. Faculdade de Medicina. Hospital das Clínicas - Brasil

^[2] Universidade de São Paulo. Faculdade de Medicina. Hospital das Clínicas - Brasil

^[3] Universidade de São Paulo. Faculdade de Medicina. Hospital das Clínicas - Brasil

• Tipo de documento: Artigo Científico
• Fonte: Brazilian Journal of Medical and Biological Research; v. 36, n. 12, p. 1769-1772, 2003-12-00.

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. (AU)

• Processo FAPESP: 96/09424-0 - Identificação da H-K-ATPase em membranas eritocritárias de ratos
• Beneficiário: Debora Lucia Bernal da Costa Seguro
• Modalidade de apoio: Bolsas no Brasil - Iniciação Científica
• Processo FAPESP: 99/00036-6 - K-atpase ouabaina insensivel eritrocitaria: aplicacao fisiopatologica.
• Beneficiário: Luis Fernando Bernal da Costa Seguro
• Modalidade de apoio: Bolsas no Brasil - Iniciação Científica