Fundamental studies of adrenal retinoid-X-receptor: Protein isoform, tissue expression, subcellular distribution, and ligand availability.

Adrenal gland reportedly expresses many nuclear receptors that are known to heterodimerize with retinoid-X-receptor (RXR) for functions, but the information regarding the glandular RXR is not adequate. Studies of rat adrenal homogenate by Western blotting revealed three RXR proteins: RXRα (55kDa), RXRß (47kDa) and RXR (56kDa). RXRγ was not detectable. After fractionation, RXRα was almost exclusively localized in the nuclear fraction. In comparison, substantial portions of RXRß and RXR were found in both nuclear and post-nuclear particle fractions, suggesting genomic and non-genomic functions. Cells immunostained for RXRα were primarily localized in zona fasciculata (ZF) and medulla, although some stained cells were found in zona glomerulosa (ZG) and zona reticularis (ZR). In contrast, cells immunostained for RXRß were concentrated principally in ZG, although some stained cells were seen in ZR, ZF, and medulla (in descending order, qualitatively). Analysis of adrenal lipid extracts by LC/MS did not detect 9-cis-retinoic acid (a potent RXR-ligand) but identified all-trans retinoic acid. Since C20 and C22 polyunsaturated fatty acids (PUFAs) can also activate RXR, subcellular availabilities of unesterified fatty acids were investigated by GC/MS. As results, arachidonic acid (C20:4), adrenic acid (C22:4), docosapentaenoic acid (C22:5), and cervonic acid (C22:6) were detected in the lipids extracted from each subcellular fraction. Thus, the RXR-agonizing PUFAs are available in all the main subcellular compartments considerably. The present findings not only shed light on the adrenal network of RXRs but also provide baseline information for further investigations of RXR heterodimers in the regulation of adrenal steroidogenesis.

Choline treatment affects the liver reticuloendothelial system and plasma fatty acid composition in diabetic rats.

PURPOSE: This study investigated effects of choline treatment on hepatic reticuloendothelial and biliary functions and plasma fatty acid composition in diabetic rats. METHODS: Diabetes was induced by streptozotocin (STZ). Choline was administered to untreated rats and a portion of STZ-treated rats for two sequences of five consecutive days, separated by a 2-day interval. Hepatic functions were studied using (99m) Tc Tin (II) colloid (TIN) and 99 mTc mebrofenin [bromo-iminodiacetic acid (BrIDA)] imaging. The TIN-uptake ratios (organ/whole body) of heart, liver and spleen, and the BrIDA-uptake ratios (organ or tissue/whole body) of liver, biliary tree and abdomen were obtained following imaging studies. Fatty acids were analysed by GC/MS. RESULTS: Choline treatment did not attenuate hyperglycaemic development. Diabetic rats showed (i) a decreased TIN-uptake ratio in liver with co-increased ratios in heart and spleen; choline treatment diminished these changes, (ii) elevated BrIDA-uptake ratios in biliary tree and abdomen but not in liver; choline treatment did not attenuate the elevations and (iii) decreases in plasma palmitoleic acid and oleic acid, reflecting an impaired stearoyl-CoA desaturase function; choline treatment did not affect the diminutions, but caused a decrease in arachidonic acid with a co-increase in linoleic acid. Some rats developed hypoproteinemia (HPO). HPO rats also exhibited decreases in plasma palmitoleic acid and oleic acid. Diabetes caused almost absence of palmitoleic acid in HPO rats. Choline treatment exerted no effect on the plasma fatty acid composition of diabetic HPO rats. CONCLUSIONS: Choline treatment affected hepatic reticuloendothelial function and plasma fatty acid composition, but not hepatobiliary function, in diabetic rats. Whether choline treatment is beneficial requires further studies.

Detection of thiopental in the steroid fraction of serum from neonates following maternal exposure.

To follow up an investigation which studied effects of antenatal dexamethasone therapy on neonatal respiratory performance in multifetal gestations, neonatal serum steroids were determined by HPLC. A major peak (X) whose retention time coincided with that of dexamethasone was observed in many, but not all, serum samples. However, there was no correlation between the neonates whose serum samples displayed this X-peak and the mothers who had actually received the steroid therapy, indicating that the X-substance was not dexamethasone. An alternate mobile phase was employed which separated the X-substance and dexamethasone validating the indication. Among ten clinical conditions of the neonate birth, the X-substance was found to correlate only with the mothers who had the cesarean operation for delivery, suggesting that the substance was not necessarily a steroid. Four anesthetic agents used for cesarean operations were studied; the X-substance was identified as thiopental using a LC/MS technique. This was based on the same retention times, the same negative ions at m/z 240.9 and the same daughter ions at m/z 100.8 between the two substances. Thus, caution must be exercised when HPLC is employed to study serum steroids of patients who have previously been exposed to thiopental. Moreover, recent reports have shown that thiopental affects certain metabolic reactions in the rat; the present findings also suggest a need for further investigations of thiopental effect on neonates.