Kinetics of system A amino acid uptake by muscle: effects of insulin and acute uremia.
Am J Physiol
; 258(5 Pt 2): F1304-10, 1990 May.
Article
en En
| MEDLINE
| ID: mdl-2186634
ABSTRACT
We found that acute renal failure (ARF) depresses maximal responsiveness to insulin of system A amino acid transport in muscle [Maroni, Karapanos, and Mitch. Am. J. Physiol. 251 (Renal Fluid Electrolyte Physiol. 20) F74-F80, 1986]. To examine mechanisms for this change, we measured the kinetics of system A in response to insulin and ARF in epitrochlearis muscle. Insulin stimulation increased the diffusion constant (KD) approximately twofold in muscles from both ARF and control rats, suggesting that insulin can modulate nonsaturable alpha-(methylamino)isobutyrate uptake. Compared with basal values, insulin did not significantly change maximal transport velocity (Vmax) in ARF or control rats; however, insulin decreased Michaelis constant (Km) by 79 and 63%, respectively. Inhibition of protein synthesis with cycloheximide did not prevent stimulation of system A by insulin. Acute uremia had no effect on nonsaturable uptake or basal system A kinetics. However, ARF produced opposing effects on insulin-stimulated system A kinetics. There was a approximately 47% decrease in Vmax, which was partially offset by a 66% reduction in Km. In summary, both insulin and ARF modulate system A kinetics by mechanisms that are independent of protein synthesis.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Uremia
/
Aminoácidos
/
Insulina
/
Músculos
Tipo de estudio:
Diagnostic_studies
Límite:
Animals
Idioma:
En
Revista:
Am J Physiol
Año:
1990
Tipo del documento:
Article