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Glucocorticoid administration decreases renal sodium/phosphate cotransport in the proximal tubule due to a down-regulation of the sodium/phosphate cotransporter but has no effect on the sodium-dependent transport of glucose or proline. The objectives of the present investigation were to determine the effects of the glucocorticoid methylprednisolone (MPL) on 1) inorganic sulfate renal clearance in rats in vivo, 2) sodium/sulfate cotransport in kidney cortex membrane vesicles, and 3) the cellular mechanism of the MPL-induced alterations in sulfate renal transport. Male adrenalectomized Wistar rats received an i.v. dose of 50 mg/kg MPL or the vehicle. Urine samples were collected for 12 h after the administration of MPL, and blood samples were collected at the midpoint of the urine collection. Other animals were sacrificed at 4, 6, and 12 h after MPL administration, and the kidney cortex was removed for RNA or membrane preparations. Kidney cortex sodium/sulfate cotransporter (NaSi-1) mRNA levels were determined by reverse transcription-polymerase chain reaction and NaSi-1 protein levels were determined by enzyme-linked immunosorbent assay. The urinary excretion rate and renal clearance of sulfate were significantly increased in MPL-treated animals (144.0 +/- 27.0 versus 65.3 +/- 21.3 micromol/12 h/kg and 0.208 +/- 0.038 versus 0. 078 +/- 0.025 ml/min/kg, mean +/- S.E., n = 9-12 in treated versus control). The V(max) value for sodium-dependent sulfate transport in brush border membrane vesicles (representing reabsorption in the proximal tubules) was significantly decreased in MPL-treated animals compared with controls (0.68 +/- 0.07 versus 0.88 +/- 0.05 nmol/mg of protein/10 s, mean +/- S.E.). There was no change in the K(m) value for sodium/sulfate cotransport in brush-border membrane and no change in sulfate/anion exchange in basolateral membrane vesicles. Membrane fluidity in brush border membrane and basolateral membrane vesicles, determined by the fluorescence polarization of 1, 6-diphenyl-1,3,5-hexatriene was unaltered by MPL treatment. NaSi-1 mRNA levels were significantly decreased at 4 and 6 h, but not 12 h, after MPL administration, whereas NaSi-1 protein expression was significantly decreased at 4, 6, and 12 h. Therefore, MPL treatment increases the renal clearance of inorganic sulfate, at least in part, due to down-regulation of NaSi-1 mRNA and protein expression in the kidney.

The renal transport and fractional reabsorption of inorganic sulfate is altered under conditions of sulfate deficiency or excess. The objective of this study was to examine the cellular mechanisms of adaptation of renal sodium/sulfate cotransport after varying dietary intakes of a sulfur containing amino acid, methionine. Female Lewis rats were divided into four groups and fed diets containing various concentrations of methionine (0, 0.3, 0.82 and 2.46%) for 8 days. Urinary excretion rates and renal clearance of sulfate were significantly decreased in the animals fed a 0% methionine diet or a 0.3% methionine diet, and significantly increased in the animals fed a 2.46% methionine diet when evaluated on days 4 and 7. Serum sulfate concentrations were unchanged by diet treatment in all animals. The fractional reabsorption of sulfate was significantly increased in the animals fed the 0% methionine diet and the 0.3% methionine diets, and decreased in the animals fed the 2.46% methionine diet. Increased mRNA and protein levels for the sodium/sulfate transporter (NaSi-1) were found in the kidney cortex following treatment with the 0 and 0.3% methionine diet groups. Sulfate homeostasis by renal reabsorption is maintained by an up-regulation of steady state levels of NaSi-1 mRNA and protein when the diet is low in methionine.

The disposition of conjugated metabolites (sulfate and glucuronide) was investigated in Eisai hyperbilirubinemic rats (EHBR) and normal Sprague-Dawley (SD) rats by in vivo and liver perfusion methods. EHBR are mutant rats that have conjugated hyperbilirubinemia as an autosomal recessive trait inheritance, and they show impaired excretion of organic anions into the bile. 6-Hydroxy-5,7-dimethyl-2-methylamino-4-(3-pyridylmethyl) benzothiazole (E3040), a novel dual inhibitor of 5-lipoxygenase and thromboxane A2 synthetase, was used as a model compound, because the major metabolites of E3040 are glucuronide and sulfate. After the i.v. injection of [14C]E3040 to EHBR and SD rats, the plasma AUC for glucuronide was greater in EHBR than in SD rats. The cumulative biliary excretion of the glucuronide was impaired to a great extent in EHBR, and the urinary excretion was enhanced. There was no significant difference in the cumulative biliary and urinary excretion of sulfate between EHBR and SD rats. The influx, efflux and sequestration rates of E3040, measured by a multiple indicator dilution method in the perfused rat liver, were similar in EHBR and SD rats. The biliary excretion of the glucuronide formed in the liver, measured by the liver perfusion method, was also severely impaired in EHBR, so the recovery of the glucuronide in the outflow specimens was markedly enhanced. The disposition of the sulfate did not change in either type of rat.(ABSTRACT TRUNCATED AT 250 WORDS)

Proximal tubular reabsorption is of primary importance in the regulation of the homeostasis of inorganic sulfate, an electrolyte that is necessary for biosynthetic and detoxification reactions. The objective of the present investigation was to determine the effect of dietary sulfate deprivation, produced by a diet low in methionine, on the renal transport of sulfate. Female Lewis rats were fed a diet containing negligible amounts of sulfate and cystine and low in methionine (0.37%) or a control diet (methionine 1.12%, cystine 0.07%) for 8 days to examine the urinary excretion rate and renal clearance of sulfate. The sulfate excretion rate was decreased by day 4 of the low methionine diet and remained low. Both the urinary excretion rates and renal clearance values were significantly decreased on day 8 (144 +/- 71 vs. 517 +/- 264 mumol/12 hr in controls, mean +/- S.D., n = 7, P < .005 and 0.38 +/- 0.19 vs. 1.07 +/- 0.61 ml min-1 kg-1 in controls, n = 5-6, P < .05, respectively), although the serum sulfate concentrations were unchanged. In vitro transport studies were performed in kidney cortex brush border membrane (BBM) and basolateral membrane vesicles isolated from rats fed either the low methionine or control diet for 7 to 9 days. The Vmax for BBM sodium/sulfate cotransport was increased in kidneys from animals that received the low methionine diet (1.1 +/- 0.10 vs. 0.75 +/- 0.08 nmol mg of protein-1 10 sec-1 in controls, n = 5, P < .001); there were no significant differences in the Km.(ABSTRACT TRUNCATED AT 250 WORDS)

A method is described for the isolation and measurement of dopamine 3-O-sulfate and dopamine 4-O-sulfate. The sulfate isomers of dopamine were synthesized chemically by the reaction of dopamine with sulfuric acid. The isomers were isolated by anion-exchange column chromatography and the identities of the two isomers were confirmed by gas chromatography coupled with mass spectrometry. A method is described for the assay of the two isomers by high-pressure liquid chromatography. When Parkinsonian patients were treated with 4.0 g/day of L-dopa, the amount of dopamine 3-O-sulfate excreted in the urine was 19.6 times that of dopamine 4-O-sulfate. When untreated Parkinsonian patients received tracer quantities of 3H-L-dopa either intravenously or orally, 3H-dopamine 3-O-sulfate was the predominant isomer but the amounts were only 3 times those of the 4-isomer. Greater quantities of both isomers were excreted when 3H-L-dopa was given orally as compared to intravenous administration. Since dopamine 3-O-sulfate is the predominant sulfate isomer, it is concluded that sulfate conjugation of dopamine could possibly compete with 3-O-methylation in determining the resultant conjugated product.

2-Butoxyethanol (BE) is a massively produced glycol ether of which more than 230 million pounds was produced in the United States in 1983. It is extensively used in aerosols and cleaning agents intended for household use. This creates a high potential for human exposure during its manufacturing and use. A single exposure of rats to BE causes severe hemolytic anemia accompanied by secondary hemoglobinuria as well as liver and kidney damage. Butoxyacetic acid (BAA) was earlier identified as a urinary metabolite of BE. In addition, we have recently identified two additional urinary metabolites of BE, namely, BE-glucuronide and BE-sulfate conjugates. The current studies were undertaken to investigate the metabolic basis of BE-induced hematotoxicity in male F344 rats. Treatment of rats with pyrazole (alcohol dehydrogenase inhibitor) protected rats against BE-induced hematotoxicity and inhibited BE metabolism to BAA. Pyrazole inhibition of BE metabolism to BAA was accompanied by increased BE metabolism to BE-glucuronide and BE-sulfate as determined by quantitative high-performance liquid chromatography analysis of BE metabolites in urine. There was approximately a 10-fold decrease in the ratio of BAA to BE-glucuronide + BE-sulfate in the urine of rats treated with pyrazole + BE compared to rats treated with BE alone. Pretreatment of rats with cyanamide (aldehyde dehydrogenase inhibitor) also significantly protected rats against BE-induced hematotoxicity and modified BE metabolism in a manner similar to that caused by pyrazole. Administration of equimolar doses of BE, the metabolic intermediate butoxyacetaldehyde, or the ultimate metabolite BAA caused similar hematotoxic effects. Cyanamide also protected rats against butoxyacetaldehyde-induced hematotoxicity. Further evidence of the involvement of metabolism in hematotoxicity was demonstrated by the administration of deuterium-labeled BE (1,1-dideuterio-2-BE) which resulted in a significant delay in the development of hematotoxicity. It is therefore concluded that: a) there is a strong correlation between the amount of BAA in the urine and BE-induced hematotoxicity; b) metabolic activation of BE via alcohol and aldehyde dehydrogenases is a prerequisite for the development of BE-induced hematotoxicity; and c) hematotoxicity induced by BE can be attributed to its metabolite BAA. Finally, the current studies may prove beneficial in the treatment of acute glycol ethers poisoning with alcohol dehydrogenase inhibitors.