Stereoselective sulphate conjugation of fenoterol by human phenolsulphotra nsferases

1. The objective of this study was to determine (1) the molecular site(s) of sulphoconjugati on of fenoterol; (2) the human phenolsulphotra nsferase (PST) isoform(s) involved; and (3) the stereochemistry of the enzymatic reaction. 2. Using the human Hep G2 cell line, hplc isolation and FAB/ms/ms, it was determined that fenoterol is sulphated both in the 4′-hydroxyphenylposition and in one of the 3′,5′-dihydroxyphenylpositions. 3. Recombinant human M-PST preferentially sulphated the 4′-hydroxyphenyl position. In contrast, recombinant P-PST exclusively sulphated the 3′,5′-hydroxyphenyl position. 4. The M-PST-catalysed sulphation of the 4′-hydroxyphenyl position was highly selective for the active RR-enantiomer, whereas the sulphation of the 3′,5′-dihydroxyphenyl position was slightly selective for the opposite SS-enantiomer. 5. The P-PST-catalysed sulphation of the 3′,5′-hydroxyphenyl position was selective for the inactive SS-enantiomer.     

Extensive Binding of the Bioflavonoid Quercetin to Human Plasma Proteins

Although the bioflavonoids, a large group of polyphenolic natural products, exert chemopreventive effects in cardiovascular disease and cancer, there is little information about the disposition of these dietary components in man. The objective of this study was to investigate the plasma-protein binding of the most abundant bioflavonoid, quercetin, using ¹⁴C-labelled quercetin. An ultracentrifugation assay (170 000 g for 16 h at 20°C) was shown to sediment plasma proteins. Binding of quercetin to normal plasma was extensive (99.1 ± 0.5%, mean ± s.d., n = 5). The unbound fraction varied as much as 6-fold, 0.3–1.8%, between subjects. This high binding was independent of quercetin concentration over the range 1.5–15 μM (0.5–5 μg mL^?1). Human serum albumin was the primary protein responsible for the binding of quercetin in plasma (99.4 ± 0.1%). Binding by α₁-acid glycoprotein (39.2 ± 0.5%) and very-low-density lipoproteins (< 0.5% of total quercetin) did not make substantial contributions to overall plasma binding. The equilibrium association constant for the binding of quercetin to serum albumin was 267 ± 33 times 10³ M^?1 (n=15). Thermodynamic data for the binding of quercetin to serum albumin indicated spontaneous, endothermic association. Displacement studies suggested that in man the ‘IIA’ subdomain binding site of human serum albumin was the primary binding site for quercetin. Association of quercetin with erythrocytes was significantly (P < 0.001) reduced by plasma protein binding. These data indicate poor cellular availability of quercetin because of its extensive binding to plasma proteins.     

ALTERATIONS IN SERUM PROLACTIN HETEROGENEITY BY PROVOCATIVE TESTS IN A PATIENT WITH A PITUITARY TUMOUR

The proportion of serum prolactin heterogeneity were investigated in a patient with a pituitary adenoma producing both prolactin and growth hormone. Glucose tolerance (GTT) and insulin tolerance (ITT) tests were performed alone and in combination with chlorpromazine both before and after hypophysectomy. Serum prolactin multiple forms were separated by Sephadex G-100 column chromatography at 3 degrees C. None of the provocative tests altered the already elevated serum prolactin either before (300 ng/ml) or after (100 ng/ml)hypophysectomy. Chlorpromazine or ITT did not alter the proportion of prolactin heterogeneity; GTT, whether in conjunction with chlorpromazine or alone and both before and after hypophysectomy, increased the proportions of the larger molecular species. In five tests in which the GTT was not performed the prolactin heterogeneity was as follows: 'void volume', 4.9%; 'big', 13.1%; 'little', 82.1%; in those experiments in which the GTT was performed the proportions of prolactin heterogeneity were: 'void volume', 13.5%, 'big', 19.2%; 'little', 67.3%.     

TATTOO REMOVAL: TANNIC ACID METHOD OF VARIOT

Background. There are many methods for tattoo removal (e.g., surgery, cryosurgery, laser, dermabrasion), but none can restore the skin to its original state. Methods. Tattoo removal was obtained with a combination of tattoo machine, tannic acid, and silver nitrate. Results. This technique proved to be effective for the removal of amateur tattoos of any size. The results with professional tattoos were much less satisfactory. The estimation of the depth of pigment in pretreatment biopsies showed no correlation with the success rate of treatment. No indication of systemic side effects on the liver from tannic acid was found in the concentration and amount used in this study. Conclusions. This technique is effective for the removal of amateur tattoos of any size and is comparable with cryotherapy, infrared coagulation, and focal salabrasion.