The absorption of pyridoxamine from the intestine of the mouse was studied in whole animals. [3H] Pyridoxamine was orally administered and the distribution of isotope between the six recognized forms of vitamin B6 was determined in portal blood after the administration. When small doses (1.4 or 14nmol) were administered, labeled pyridoxamine could hardly be found in the portal blood, although labeled pyridoxal and pyridoxal phosphate were found in the same blood. However, when a large amount (46 or 140nmol) was given, a significant amount of labeled pyridoxamine was found with labeled pyridoxal and pyridoxal phosphate in the portal blood. These results suggest that a physiological dose of pyridoxamine is rapidly transformed to pyridoxal in the intestial tissues and then released in the form of pyridoxal into the portal blood.
The vitamin C activity of 2-O-α-D-glucopyranosyl-L-ascorbic acid (AA-2G), which is one of chemically stable derivatives of L-ascorbic acid (ASA), in guinea pigs was investigated. Male guinea pigs were divided into 9 groups and fed AsA-deficient diet for 24 days with the following supplement: AA-2G- or AsA-supplemented groups were orally supplemented with 0.96, 1.92, 9.6 and 192 AA-2G mg/animal/day or equimolar amounts of AsA (0.5, 1, 5 and 100mg/animal/day, respectively); AsA-deficient group received neither of them. The body weight gain, serum alkaline phosphatase activity, and the concentration of AsA and AA-2G in the liver, adrenals and urine of the guinea pigs were measured at the end of the experimental period. The AA-2G-supple-mented guinea pigs showed similar body weight gain to the animals sup-plemented with equimolar amount of AsA. Serum alkaline phosphatase activity in both AA-2G- and AsA-supplemented groups was significantly higher than that of AsA-deficient group. But there was no significant difference between the groups supplemented with AA-2G and the equimolar amount of AsA. AA-2G-supplemented guinea pigs showed no apparent symptoms of scurvy. In AA-2G-supplemented groups, AA-2G was not detected in the liver, adrenals and urine, but AsA was found and the AsA concentration increased with increasing AA-2G dosage. The AsA concentration in the tissues of each AA-2G-supplemented groups was higher than that of AsA-deficient group, which was similar to that of the groups supplemented with equimolar amount of AsA. These results showed that AA-2G has the same vitamin C activity as AsA on a molar basis for the orally supplemented guinea pigs.
The effect of dietary protein on the body fat accumulation was studied in rats. Adult rats weighing about 300 g were fed 21% protein (casein or soybean protein isolate) and 5% oil diets by pair-feeding for 65 days in Experiment 1. In Experiment 2, only protein and oil contents were changed, 25 and 10%, respectively. Final body weights of the two dietary groups were similar in both experiments, especially in Experiment 2. Total body fat was slightly lower in the soybean protein diet group than in the casein diet group in Experiment 2, only when it was expressed as the percentage against body weight. However, intra-abdominal fat was significantly lower in the soybean protein diet groups than in the casein diet groups in both experiments. Serum lipid levels were greatly lower in the soybean protein diet group than in the casein diet group in Experiment 2 (the data were not available in Experiment 1). The results suggest that dietary soybean protein has the effect to lower the intra-abdominal fat accumulation as compared with casein.
We studied the effects of a synthetic adrenocortical steroid, dexamethasone, on the development of experimental atherosclerosis in cholesterol-fed rabbits. Daily intramuscular injection of dexamethasone (0.125mg/day) remarkably inhibited the aortic atherosclerosis induced by feeding a 1% cholesterol-rich diet for 8 weeks, although it aggravated diet-induced hyperlipidemia. Histologically, less foam cell accumulation was observed in the atherosclerotic lesions of the dexamethasone-treated rabbits as compared with the control animals. When rabbits were fed a normal chow diet for 10 weeks after receiving the 1% cholesterol-rich diet for 8 weeks, no regression of atherosclerotic lesions was observed with the daily injection of dexamethasone (0.125mg/day); however, the drug again tended to inhibit further progression of atherosclerosis. The anti-atherogenic mechanism of dexamethasone may involve an inhibition of recruitment of blood monocytes and the insudation of atherogenic lipoproteins, mainly β-very low density lipoprotein (β-VLDL) in the present experiments, into the aortic intima, or it may involve a change in the size and structure of the lipoproteins, resulting in their decreased passage through the aortic endothelium into the intima.
The small intestinal disaccharidase activity and its daily variation in the diabetic rat have not been well described. Therefore, the small intestinal disaccharidase (maltase, lactase and sucrase) activity and its daily profile were studied in streptozotocin-induced diabetic rats under physiological conditions. In diabetic rats, a similar pattern of diurnal variation of disaccharidase activity to control rats was observed, while the relationships between daily change of disaccharidase activity and that of food consumption suggested that there was a different mechanism of diurnal variation in diabetic rats. On the other hand, a significant increase of mean 24-h lactase and sucrase activities was noted in diabetic rats, while that of maltase was not significant. Using the in vitro incubation method, a significant correlation between glucose concentration and lactase or sucrase activity but not maltase activity was observed. However, insulin showed no effect on disaccharidase activity. Thus we clarified the presence of a diurnal variation of disaccharidase activity and an increase in its activity in diabetic rats. This change was suggested to be derived from high plasma glucose level.
To examine whether sugar alcohol affects intestinal calcium absorption, 5-week-old male Wistar rats were fed a basal diet (66% starch) or the diets containing either 10% maltitol, 10% sorbitol or 10% lactose. At 2 and 6 weeks after the start of feeding, the animals were subjected to 5-day-period calcium balance study. Feeding maltitol diets as well as sorbitol diet led to a significantly elevated intestinal calcium absorption and calcium retention. Lactose diet did not produce an increased intestinal calcium absorption in the condition used in the present study. To explore whether maltitol can exert its effect in a short period of time, the rats were starved for 16 h and were fed by a poly-ethylene tube the diet containing 0.44% calcium together with either 10% maltitol or 10% glucose. The total calcium remaining in the gastroin-testinal tract at 6 h after feeding was significantly decreased in the rats given maltitol diet as compared to the rats given glucose diet. When 10μCi of 45CaCl2 was given orally with the diets containing maltitol or glucose, the amount of 45Ca remaining in the gastrointestinal tract at 6 h after its administration was smaller in the rats fed maltitol diet than in the rats fed glucose diet. These results suggest that both di- and mono-saccharide alcohols might affect intestinal epithelium, resulting in an enhanced intestinal calcium absorption.
Pectin, guar gum, transgalactosylated oligosaccharide and glucose were estimated as substrate for hindgut fermentation by meas-uring the volume of gas released from a 1ml scale batch culture using rat cecal contents. The amount of short-chain fatty acids (SCFA) in cultures of glucose and pectin was also measured. The amount of SCFA (Y μmol/ culture) or volume of gas released (Y ml/culture) was expressed as an exponential function of incubation time (t) (Y=A+B× (1-e-kt); A, B and k are constants). The amount of potential production of gas and SCFA (B) for glucose was higher than that for pectin and the rate constant of gas and SCFA (k) for pectin was higher than that for glucose. The volume of gas released (ml/culture) correlated positively and linearly with the amount of total SCFA (acetic, propionic and n-butyric acids, μmol/culture). A single regression stood for both glucose and pectin. The gas release followed saturation kinetics. The half maximal concen-tration and maximal velocity for gas release from pectin were higher than those from other substrates (glucose, guar gum and transgalactosylated oligosaccharide).
Japanese soybean paste miso, which has been reported to prevent gastric and mammary cancer and chronic nephritis, was dem-onstrated by electron spin resonance spectrometry using 5, 5'-dimethyl-1 -pyrroline-N-oxide as a scavenger of free radicals. Fifty mg/ml of miso scavenged 100% of 1, 1-Biphenyl- 2 -picrylhydrazyl radicals (3.9×1015 spins/ml); 45 mg/ml quenched 92% of hydroxyl radicals (7.9×1016 spins/ml); and 50 mg/ml quenched 50% of superoxide anion (6.7×1016 spins/ml). In the system of rat cerebral cortex homogenate supplemented with 2mM each of Fe2+ and ascorbic acid, 90% and 82% of the hydrogen and carbon-centered radicals having 1.7×1013 spins/ml and 3.9×1013 spins/ml, respectively, were quenched by 180mg/ml of miso. The thiobarbituric acid-reactive substances, an index of lipid peroxidation in the brain, was inhibited by 10mg/ml of miso. These results showed that miso acts as an antioxidant by scavenging free radicals.