Pituitary gland ascorbic acid

The adrenal glands and pituitary glands have the highest tissue concentration of ascorbic acid. The brain, Hver, and spleen, however, represent the largest contribution to the body pool. Plasma and leukocyte ascorbic acid levels decrease with increasing age (152). Elderly people require higher ascorbic acid intakes than children to reach the same plasma and tissue concentration (153). 

Ascorbic acid is photosensitive and unstable in aqueous solution at room temperature. During storage of foods, vitamin C is inactivated by oxygen. This process is accelerated by heat and the presence of catalysts. Ascorbic acid concentration in human organs is highest in adrenal and pituitary glands, eye lens, liver, spleen, and brain. Potatoes, citrus fruits, blade currants, sea buckthorns, acerola, rose hips, and red paprika peppers are among the most valuable vitamin C sources [1,2]. 

Different concentrations in compartments that can exchange ascorbic acid may also be achieved by nonlinear transfers such as active transport processes. Nonlinearity, however, cannot be determined by experimental designs using only one steady state level. The brain, adrenals, pituitary gland, and eyes take up ascorbic acid by an energy-dependent active transport mechanism (30,31). 

The oxidative product of ascorbic acid, dehydroascorbic acid, is the preferred form of the vitamin for uptake by neutrophils, erythrocytes, and lymphocytes (27). Once within the erythrocyte, dehydroascorbic acid is reduced to ascorbic acid by a glutathione-dependent, dehydro-ascorbic-acid-reducing enzyme (20,28). However, the reduced form of ascorbic acid is found in most other tissues, that is, liver, lungs, kidneys, skin, and pituitary and adrenal glands (20,29). From these studies, ascorbic acid is taken up by several tissues by an energy-dependent and Na -sensitive process, but the transport of the oxidized vitamin form follows the principles of diflFusion. 

The pituitary gland distinguishes itself by having a rather high content of ascorbic acid. The only systematic study on the variation with age in... 

Fig. 6. Variation with age in ascorbic acid concentration of human pituitary gland. The curve is constructed on the basis of data reported by Schaus (1957).

Ascorbate and Hormone Balance. The highest concentrations of ascorbate are found in the adrenal and pituitary glands, and the terminal stages of scurvy are just preceded by complete depletion of adrenal ascorbate, leading, it has been frequently stated, to scurvy death from adrenocortical failure. This has caused many to suggest that the ascorbic acid-dehydroascorbic acid system plays an important role in the synthesis and release of hormones of the adrenopituitary axis. The evidence for this is both conflicting and confusing (13, 72, 73,102, 277, 278). 

The human tissues with particularly high ascorbic acid concentrations are the organs with intensive metabolism like pituitary gland, adrenal glands, eye lens, liver, pancreas, spleen, and brain. 

Ascorbic acid (L-3-keto-threo-hexuronic acid-7-lactone. Formula 6.18, I) is involved in hydro-xylation reactions, e. g., biosynthesis of catecholamines, hydroxyproline and corticosteroids (11-P-hydroxylation of deoxycorticosterone and 17-P-hydroxylation of corticosterone). Vitamin C is fully absorbed and distributed throughout the body, with the highest concentration in adrenal and pituitary glands. 

In these experiments, the extract was injected intravenously into the test rats which were bled 10 min later from the jugular vein. The effect of the extract on plasma LH activity of the test animals was estimated by the ovarian ascorbic acid depletion test. The factor has been found to be effective in a variety of situations. It is active in normal female rats and in ovariectomized rats in which the release of LH has been inhibited either by administration of gonadal steroids or by lesions in the median eminence (ME) (2). This latter observation is important because it indicates that the LRF acts directly on the anterior pituitary to release LH. An indirect action via the nervous system would have been blocked by these lesions which interrupted neural control over LH secretion. Further evidence that the LRF acts directly on the gland to release LH has been provided by the experiments of Campbell t l. (7) in rabbits and Nikitovitch-Winer (8) in rats. They showed that infusion of hypothalamic extract directly into the anterior lobe of the pituitary could evoke ovulation. Systemic administration of the same dose of extract was without effect. Schally Bowers (9) have demonstrated an LH-releasing action of h3rpothalamic extracts on pituitaries incubated vitro and we have recently confirmed this observation (Watanabe Ratner, unpublished data, 1965). This provides further evidence that LRF acts directly on the h3rpophysis. 

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