Ascorbic acid pancreas

Scheller et al. (1986a) combined polyurethane-immobilized LOD with an Au/Pd-sputtered carbon electrode. The electrode modification permits H2O2 to be electrochemically oxidized at a potential as low as +450 mV, where interferences by other anodically oxidizable compounds such as NADH and ascorbic acid are largely reduced (Fig. 57). This increased selectivity also enables the measurement of LDH activity. The sensor has been introduced in an FIA manifold. A sample frequency of 200Ai (Fig. 58) and a CV below 1% were obtained with this setup. A platinum electrode with LOD covalently bound to a nylon membrane has been employed for continuous blood lactate determination in an artificial pancreas by Mascini et al. (1985b, 1987). 

In a screening procedure for characterization of lipase selectivity, Bradoo et al. [90] esterified sucrose and ascorbic acid with different fatty acids in a microwave oven using porcine pancreas, B. stearothermophilus SB-1 and B. cepacia RGP-10 lipases. Microwave-assisted enzyme catalysis was found to be an attractive procedure for rapid characterization of a large number of enzyme samples and substrates this would otherwise have been a cumbersome and time-consuming exercise. 

The so-called activation of lipase action by proteins such as egg albumin or gelatin (322), by serum (65), and by inactivated serum (323) is probably primarily the restilt of better emulsification of the substrate. Amino acids and polypeptides, especially those containing glycine, are reported as very effective activators (324). Of several amino acids tested, histidine was found to be the most effective and more so than histamine (325, 326). The activation of lipase action by gall bladder extracts may also be a result of amino acids present in the extract (327). Extracts of small intestine or pancreas of the chick lost from a third to a half of their lipase activity after 2 hours of dialysis, and the activity was partially restored by ad tion of histidine or ascorbic acid (328). Wills (280), however, was unable to activate a preparation of purified lipase by histidine or any other amino acid tested, but found that histidine and several other amino acids were excellent protectors of lipase against the toxic effects of small amounts of metals such as Cu++. He concluded that amino aeid activation effects might be explained on this basis. 

On the basis of assays made by Yavorsky et al. (1934), the ascorbic acid concentration of the human pancreas shows a definite tendency to decrease with age. The mean values found for infants, children, adults, and persons aged 46-77 years were, respectively, 37, 23, 15, and 10 mg %. 

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. 

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