EFFECT OF D-GLUCOSE AND L-GLUTAMATE ON THE KINETICS OF BICARBONATE REABSORPTION IN VAT PROXIMAL TUBULES

EFFECT OF D-GLUCOSE AND L-GLUTAMATE ON THE KINETICS OF BICARBONATE REABSORPTION IN VAT PROXIMAL TUBULES

Author Gomes, Guiomar Nascimento Autor UNIFESP Google Scholar
Aires, Margarida de Mello Autor UNIFESP Google Scholar
Institution Universidade de São Paulo (USP)
Universidade Federal de São Paulo (UNIFESP)
Abstract The effect of D-glucose or L-glutamate on the kinetics of bicarbonate reabsorption in the early (EPT) and middle proximal tubule (MPT) was studied in vivo in Munich-Wistar rats by microperfusion techniques. The presence of 20 mM D-glucose in the lumen increased acidification half-time (t/2) (from 2.54 +/- 0.09 s to 3.11 +/- 0.17 s in EPT and from 4.75 +/- 0.20 s to 6.04 +/- O.49 s in MPT). Bicarbonate reabsorption (JHCO(3)(-)) decreased as a consequence of this change (from 3.80 +/- 0.17 to 2.46 +/- 0.20 nmol cm(-2) s(-1) in EPT and from 2.30 +/- 0.10 to 1.64 +/- 0.10 nmol cm(-2) s(-1) in MPT). In this situation the basolateral membrane potential difference (BLMPD) in the MPT decreased from -41.6 +/- 2.47 to -29.7 +/- 2.45 mV and returned to control values after perfusion with D-glucose. The addition of 20 mM L-glutamate to the luminal perfusion caused an opposite effect, i.e., a decrease in t/2 (1.54 +/- 0.21 s in EPT and 3.25 +/- 0.26 s in MPT) and a consequent increase in JHCO(3)(-) in both segments (5.09 +/- 0.58 nmol cm(-2) s(-1) in EPT and 3.92 +/- 0.30 nmol cm(-2) s(-1) in MPT). The BLMPD of MPT increased during L-glutamate perfusion (-39.0 +/- 2.48 mV in control and -52.0 +/- 2.72 mV with L-glutamate) and returned to control values after perfusion. The results observed may be the consequence of coupled Na+-substrate transport altering the BLMPD which modifies the electrical driving force for coupled Na+-HCO3- efflux across the basolateral membrane. The alteration of this process may in turn affect intracellular pH, which is an important modulator of luminal Na+/H+ exchange. This possibility is supported by the observed depolarization of BLMPD by D-glucose (electroneutral molecule), and hyperpolarization by glutamate anion.
Keywords PROXIMAL TUBULAR
ACIDIFICATION
GLUCOSE REABSORPTION
GLUTAMATE REABSORPTION
Language English
Date 1995-07-01
Published in Brazilian Journal Of Medical And Biological Research. Sao Paulo: Assoc Bras Divulg Cientifica, v. 28, n. 7, p. 805-811, 1995.
ISSN 0100-879X (Sherpa/Romeo, impact factor)
Publisher Assoc Bras Divulg Cientifica
Extent 805-811
Access rights Closed access
Type Article
Web of Science ID WOS:A1995RT00500013
URI http://repositorio.unifesp.br/11600/43088

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