- 作者: Mieczystaw Pokorski Magdalena Marczak Aneta Dymecka Piotr Suchocki
- 作者服務機構: Department of Respiratory Research, Medical Research Center, Polish Academy of Sciences, Warsaw, and Deparment of Drug Analysis, Warsaw Medical University, Warsaw, Poland
- 中文摘要: --
- 英文摘要:
We have investigated the hypothesis that a lipid-soluble
derivative of ascorbic acid, ascorbyl-6-palmitate (AP),
could serve as a carrier of ascorbate into neural tissues.
Ascorbate could then exert its physiological effects in the
biomembranes that are the target sites of the cellular sig-
naling pathways which are normally hardly accessible to
this water-soluble compound. The potential role of AP
would require that it penetrates into tissues. The major
objective of the study was to determine whether ascor-
bate could be recovered from cerebral cortex and carotid
body tissues, both sensitive to the hypoxic stimulus,
after AP given by gavage. Biological samples were ana-
lyzed by HPLC for the determination of ascorbate. We
found that ascorbate was recovered from the tissues
studied. Its content was higher in both tissues, by nearly
an order of magnitude, after ingestion of AP than after
ingestion of ascorbic acid, and the ascorbate level was
higher in the carotid body than in the cortex. Hypoxia
decreased the ascorbate content which implies physio-
logical activity of ascorbate carried alongside the AP
molecule. The lipophilic AP was able to cross biological
The physiologicl importance of L-ascorbic acid (AA)
or ascorbate chiefly stems from its ability to act as an
antioxidant or reducing agent. AA accumulates most at
key functional sites, for instance, in the brain, where it
reaches levels far higher than in blood [10,19]. AA does
not cross the blood-brain barrier. It is moved against the
concentration gradient due to the action of a glucose
transporter in endothelial cells and a Na+-dependent AA
transporter in neuroepithelial cells [7]. Both transport sys-
tems require energy which may limit ascorbate's tissue
availablility, in particular during increased functional de-
mand. Another limitatioin is that ascorbate, as a water-
soluble molecule, is hardly able to penetrate phospholipid
bilayers of biomembranes. These membranes, especially
neuronal ones, are not only the target sites for signaling
cascades, but also the most molecularly dense cellular
areas and as such highly vulnerable to free radical attacks
and the disintegration action of stressful conditions, such
as hypoxia[8]. - 中文關鍵字: --
- 英文關鍵字: Antioxidants. Ascorbate. Ascorbyl palmitate. Carotid Body. Cat. Ascorbate synthesis. Cellular Membranes. HPLC. Hypoxia. Cerebral Cortex