Sulphate conjugation of p-hydroxytriamterene by platelet phenol sulphotransferase: assay conditions and correlation with metabolism in man

Purification and characterization of human liver phenol-sulfating phenol sulfotransferase

The phenol-sulfating form of phenol sulfotransferase (P-PST) was purified and characterized from human liver cytosol using DEAE-cellulose, Sephacryl S-200, and 3',5'-diphosphoadenosine-agarose affinity chromatography. During the purification procedure, P-PST was resolved from the monoamine-sulfating form of phenol sulfotransferase (M-PST) and dehydroepiandrosterone sulfotransferase, which are also present in human liver cytosol. P-PST activity was purified 560-fold as compared to liver cytosol and the purified enzyme possessed a specific activity of 340 nmol phenol sulfated per minute per milligram protein. Enzymatically active P-PST has an apparent molecular size of 68,000 Da as determined by Sephacryl S-200 chromatography and a subunit molecular weight of 32,000 Da as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, suggesting that P-PST exists in vivo as a homodimer. Antibodies raised to human platelet M-PST cross-reacted strongly with pure P-PST suggesting the two PSTs are structurally closely related. Two types of P-PST activity have been identified in different human livers by their thermostability and elution during anion-exchange chromatography. Each of the livers examined possessed only one type of P-PST activity. Both types of P-PST were shown to possess the same subunit molecular weight and immunoreactivity, whereas the differences in thermostability of the two P-PST activities appeared to be related to the method of preparation of liver cytosol. Both types of P-PST activity were inhibited to similar extents by incubation with 50 microM N-ethylmaleimide or 5 mM phenylglyoxal. These results suggest that the two types of P-PST in different human livers are very similar and probably represent different allelic forms of the enzyme.

Deconjugation of p-hydroxytriamterene sulphate in the rat

1. The extent of deconjugation of p-hydroxytriamterene sulphate was studied in rats, by h.p.l.c., after i.v., i.p., and oral administration. 2. After i.v. administration, deconjugation accounted for 29-54% of the recovered dose as free p-hydroxytriamterene in urine and faeces. Following i.p. administration, 70-88% was deconjugated and 72-96% was deconjugated after oral administration. Most of the p-hydroxytriamterene was recovered in faeces.

Sulfation of minoxidil by human platelet sulfotransferase

In an attempt to determine whether (1) sulfotransferase activity in human platelets would convert minoxidil to minoxidil sulfate and (2) inter-subject variations in this sulfotransferase activity could be noted, platelet homogenates were incubated with minoxidil and 35S-PAPS in HEPES buffer at 37 degrees C for 30 min. Radioactivity which was extracted into ethyl acetate and shown by HPLC to elute with authentic minoxidil sulfate was counted by scintillation counting. Aliquots of the platelet homogenates were also preincubated at 43 degrees C for 15 min to determine the thermal stability of the sulfotransferase activity. Sulfotransferase activity in platelets from 48 adult males ranged from 0.9-13.2 pmol minoxidil sulfate produced/10(7) platelets per 30 min (mean 4.91 +/- 2.84 pmol/10(7) platelets per 30 min +/- SD). Thermal stable sulfotransferase activity ranged from 0.2-7.6 pmol minoxidil produced/10(7) platelets per 30 min and varied from 15 to 57% of the total sulfotransferase activity. Thus, the results indicate that human platelets can effect the sulfation of minoxidil and that sulfotransferase activity does show inter-subject variation.

The true composition of kidney stones passed during triamterene therapy

The potassium-sparing agent triamterene and its metabolites have been identified as components of kidney stones passed by patients receiving that drug. We have analyzed 66 such kidney stones by use of quantitative thin-layer chromatography. The stones contained not only the unchanged triamterene but also significant amounts of an intermediate metabolite, hydroxytriamterene, and large amounts of the sulfate ester of hydroxytriamterene. Of the stones 49 per cent contained less than 5 per cent triamterene and its metabolites, and no stone comprised 100 per cent triamterene-derived material. Of all the triamterene-related material unchanged triamterene dominated. However, the relative fractions of triamterene and hydroxytriamterene in the kidney stones exceeded the relative fractions of these 2 components in the urine.