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Am J Physiol Regul Integr Comp Physiol 280: R1627-R1631, 2001;
0363-6119/01 $5.00
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Vol. 280, Issue 6, R1627-R1631, June 2001

In vitro and in vivo evaluation of proximal tubular acidification in aging rats

Myriam Mac Laughlin1, María Cristina Damasco2, Pilar Igarreta2, and Carlos Amorena1,3

1 Instituto de Investigaciones Cardiológicas, Facultad de Medicina, 1122 Buenos Aires; 2 Programa de Regulacion Hormonal y Metabólica, Consejo Nacional de Investigaciones Centíficas y Técnicas, Departamento de Química Biológica, Facultad de Ciencias Exactas y Naturales, 1428 Universidad de Buenos Aires, Buenos Aires; and 3 Escuela de Ciencia y Tecnología, Universidad Nacional de Gral San Martín, 1650 San Martín, Argentina

The normal aging process is accompanied by a progressive deterioration of renal function. We studied the kinetics of proximal tubular acidification of young (3 mo) and aging (22 mo) rats using in vivo and in vitro techniques. Blood acid-base parameters were similar in both groups. The maximum velocity of the Na+/H+ exchange (NHE) in brush-border membrane vesicles (BBMV) showed a 72% decrease in aging compared with young rats, whereas the Michaelis constant remained unchanged. The NHE3 isoform of the Na+/H+ exchanger was detected in BBMV by Western blot in both groups, and a decrease of 90% in the abundance was observed in aging rats. Micropuncture experiments with simultaneous luminal and peritubular perfusion with phosphate Ringer and continuous measurement of intratubular pH showed an acidification rate constant 34% smaller in aging compared with young rats. Proton flux was 48% lower in aging than in young rats. The present results suggest that proximal tubular acidification is impaired with aging.

Na+/H+; vesicles; micropuncture


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 Am. J. Physiol. Regul. Integr. Comp. Physiol.Home page
P. B. Persson
Aging
Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2002; 282(1): R1 - R2.
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