Endothelial cells may play a potential role in cholesterol efflux from peripheral tissues to liver. Cholesterol efflux from cells is essential for activation of the reverse cholesterol transport pathway and cardiovascular health. One of the cholesterol transporters is steroidogenic acute regulatory protein (StAR) which promotes intramitochondrial delivery of cholesterol to the cholesterol side-chain cleavage system. The aim of the present study was to determine the effects of a niacin-chromium complex on aortas of hyperlipidemic rats and on the cholesterol efflux from aorta endothelial cells by examination under light and transmission electron microscopes and evaluating the StAR immunoreactivity, respectively. Aorta lipid peroxidation (LPO) and glutathione (GSH) levels were determined by spectrophotometric methods. After treating hyperlipidemic animals with the complex, the StAR immunoreactivity in endothelial cells increased to achieve cholesterol homeostasis and efflux. Combined treatment with niacin and chromium resulted in an inhibition in the mast cell secretion and a decrease in lipid vacuole size in unilocular adipose tissue surrounding aorta, as well as in a decrease in morphological degenerations observing in aorta of hyperlipidemic rats. Aorta LPO levels increased and GSH levels decreased in the hyperlipidemic group, whereas treatment with niacin and chromium reversed these effects. In conclusion, this study reveals that combined treatment with niacin and chromium prevents the morphological and biochemical changes observed in thoracic aorta of hyperlipidemic rats, and may regulate effectively cardiovascular diseases inducing an increase in StAR levels on endothelial cells.
Abstract:The dorsal and ventral skin in amphibians plays an important role in osmoregulation. Prolactin hormone is involved in regulation of amphibian skin functions, such as water and electrolyte balance. Therefore, amphibians may be useful as a model for determining the sites of the prolactin receptor. In this study, prolactin receptor was detected in frog dorsal and ventral skin using immunohistochemical staining method. Prolactin receptor immunoreactivity was localized in all epidermal layers except stratum corneum of dorsal skin epidermis, stratum germinativum layer of ventral skin epidermis, myoepithelial cells, secretory epithelium and secretory channel cells of granular glands in both skin regions. The mucous glands and secretory granules of granular glands did not show immunoreactivity for the prolactin receptor. According to our immunohistochemical results, the more widespread detection of prolactin receptor in dorsal skin epidermis indicates that prolactin is more effective in dorsal skin. Presence of prolactin receptors in epidermis points out its possible osmoregulatory effect. Moreover, detection of receptor immunoreactivity in various elements of poison glands in the dermis of both dorsal and ventral skin regions suggests that prolactin has a regulatory effect in gland functions.
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