Dynamics of renal excretion of phenol and major metabolites in the rainbowtrout (Oncorhynchus mykiss)

Renal excretion of phenol (PH), phenyl glucuronide (PC), phenyl sulfate (PS ), and hydroquinone (HQ) was determined in 600-900 g rainbow trout (Oncorhy nchus mykiss) continuously exposed (144-h) to waterborne PH (5 mg l(-1) or 53.2 mu mol l(-1)) in respirometer-metabolism chambers. The 'free' plasma c oncentration time course was obtained from samples withdrawn from a dorsal aortic cannulae, while the urine concentration time course was acquired usi ng a bladder catheter. Microdialysis and HPLC techniques were used to isola te and identify PH and metabolites. Plasma and urinary PH were at steady-st ate in 4 h. PG aad HQ in both plasma and urine continued to rise throughout 144 h. PS values in plasma reached a maximum around 48 h, while urine PS p lateaued near 24 h. Of the net PH gill uptake at steady-state (144 h), as m uch as 50% was eliminated in the urine (PG = 81, PS = 16, PH = 4%) and the rest extrarenally. PS kinetics suggested the existence of a high affinity/l ow capacity pathway, while PG production was suggestive of a low affinity/h igh capacity formation pathway. Rainbow trout glomerular filtration rate (G FR) was 6.10 ml kg(-1) h(-1), which was 30% higher than the mean urine flow rate (UFR) of 4.28 ml kg(-1) h(-1). Renal Clearance (Cl-x) calculated for PH, PG, PS and HQ were 4.12, 8.67, 24.33 and 1.85 ml kg(-1) h(-1), respecti vely. Urine Clearance Ratios (Cl-x/GFR) were 0.69, 1.56, 5.49 and 0.30 for PH, PG, PS and HQ, respectively. The results of this study support in vivo tubular secretion in freshwater adapted trout for both PG and PS, and sugge st a possible kidney secretory transport maxima for sulfate conjugates. (C) 1999 Elsevier Science B.V. All rights reserved.