Renal dopamine production and release in the rat: a microdialysis study

Interstitial fluid analysis for assessment of organ function

Evaluation methods are required for non-heart-beating donor (NHBD) kidneys to ensure the success of transplantation. In this study, the microdialysis technique was employed for the ex-vivo assessment of hypothermically preserved NHBD kidney function. Microdialysis probes were placed in the renal cortex of 2 h warm ischaemic porcine kidneys to monitor interstitial pyruvate dynamics during hypothermic machine perfusion with perfusate containing 29.4 mM fructose-1,6-diphosphate (FDP). The presence of exogenous FDP in the perfusate induced no changes in the renal flow rate and vascular resistance, renal artery effluent biochemistry, or pyruvate concentration relative to untreated control kidneys. Significant increases in pyruvate production (P < 0.05), however, were observed after 12 h of perfusion in the interstitial fluid of FDP-treated kidneys relative to control kidneys. After 24 h of perfusion, interstitial fluid concentrations of pyruvate were 149.1 +/- 58.4 vs. 55.6 +/- 17.9 micro M (P < 0.05) in the FDP and control group, respectively. The microdialysis probe collected the interstitial fluid directly from the cellular sites of metabolic and synthetic activity, where perfusate dilution was minimal. Consequently, the biochemical changes induced by the organ metabolic activity were detected only at the interstitial level, in the microdialysates. Interstitial fluid pyruvate may be a good indicator of kidney function. The addition of FDP to the perfusion solution during ischaemic kidney preservation resulted in enhanced pyruvate production in the extracellular space, indirectly reflecting an increase in anaerobic ATP production. The pyruvate will be transformed during organ reperfusion into acetyl Co-A enzyme allowing an immediate start of aerobic metabolism. This in turn can increase the amount of ATP available to the cells and may help prevent reperfusion injury upon transplantation.

Understanding renal dose dopamine

Low-dose dopamine is a widely administered drug used often in critical care settings to prevent or treat patients with low urinary output. There are new data to support that low-dose dopamine may have side effects and not always increase renal perfusion to the kidneys. This article is a review of the current use of low-dose dopamine, the role of dopamine in the kidneys, and the potential risks of infusing this drug to patients.

Simultaneous determination of 3,4-dihydroxyphenylacetic acid and homovanillic acid using high performance liquid chromatography-fluorescence detection and application to rat kidney microdialysate

We established a sensitive and simultaneous determination method of 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) using HPLC-fluorescence detection. This method adopted the column-switching system, which included an on-line extraction of carboxylic acids by a strong anion-exchange column followed by separation on an ODS column, coulometric oxidation, fluorogenic reaction with ethylenediamine, and fluorescence detection. The detection limits were 50 and 100 fmol/injection for DOPAC and HVA, respectively (a signal-to-noise ratio of 3). The method was applicable to 50 microl of rat kidney microdialysate with a sufficient accuracy and precision. The concentrations of DOPAC and HVA in rat kidney microdialysate were 131+/-29 and 404+/-44 nM, respectively (n=5). This is the first report of DOPAC and HVA quantified in rat kidney microdialysate.