IngentaConnect Effects Of Glycine On Glomerular Filtration Rate And Segmental Tu...

Abstract:

SUMMARY

1. Infusion of the amino acid glycine leads to an increase in effective renal plasma flow (ERPF) and glomerular filtration rate (GFR) by a mechanism that possibly involves stimulation of nitric oxide (NO). Because NO also increases proximal tubular fluid output (V_prox) by inhibition of proximal tubular Na⁺ reabsorption and modulation of the tubuloglomerular feedback system, we hypothesized that glycine would increase V_prox as measured by lithium clearance (C_Li).

2. In the first series of experiments, the effect of glycine infusion (4 mg/min) was examined in conscious, unstressed, chronically catheterized rats. In an additional series of experiments, the effect of glycine was examined under similar conditions in rats pretreated with a NO synthase (NOS) inhibitor (N^G-nitro-L-arginine methyl ester (L-NAME), 2.5 μg/min).

3. Glycine significantly increased ERPF (from 3268 to 4018 μL/min per 100 g bodyweight (BW)), GFR (from 874 to 1009 μL/min per 100 g BW), C_Li (from 275 to 461 μL/min per 100 g BW) and Na⁺ clearance (C_Na; from 2.9 to 14.0 μL/min per 100 g BW). Fractional excretion of lithium (FE_Li; from 32 to 46%) and C_Na/C_Li (from 0.99 to 2.99%) also rose, indicating inhibition of proximal and distal nephron Na⁺ reabsorption, respectively. In the rats pretreated withL-NAME, similar haemodynamic and tubular responses to glycine infusion were seen, suggesting that the effects were not mediated by NO.

4. We conclude, that glycine increases ERPF and GFR and it also inhibits proximal and distal nephron Na⁺ reabsorption leading to an increase in C_Li and C_Na. There was no indication that any of these effects were mediated by NO.

Keywords: conscious rats; glomerular filtration rate; kidney function; lithium clearance; nitric oxide; renal functional reserve

Document Type: Research article

DOI: 10.1046/j.1440-1681.2002.03683.x

Affiliations: 1: Institute for Basic Psychiatric Research, Department of Biological Psychiatry and 2: Medical Research Laboratories and Institute of Experimental Clinical Research, Aarhus University Hospital, Denmark

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Effects Of Glycine On Glomerular Filtration Rate And Segmental Tubular Handling Of Sodium In Conscious Rats