The effect of dietary calcium levels on fecal steroid excretion was examined in four-week-old male rats. We studied rats fed three levels of calcium (0.5, 1.0 and 1.5g/100g diet) with a 5.0% dietary lipid content. It was shown that increasing the calcium level in the diet increased fecal dry weight and decreased the gastrointestinal transit time. The daily fecal excretion of total lipids and cholesterols was increased by dietary calcium supplementation, but daily fecal excretion of total bile acids was not affected. These results suggest that high dietary calcium inhibits the absorption and reabsorption of total lipids and cholesterols in the gastrointestinal tract, but does not inhibit excretion total bile acids.

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Digestibilities of high-amylose corn starch (HAS) and normal corn starch (CS) were determined and compared in ileorectostomized and normal rats fed diets containing graded levels of HAS (10, 20, 40 and 65.5%, respectively). Dietary supplementation of HAS was done at the expense of sucrose. In the ileorectostomized rats, the digestibility of CS was more than 99%, irrespective of its dietary level, whereas that of HAS was reduced in accordance with the increase in the dietary level (67-74%). In normal rats, the digestibility of HAS was also reduced in accordance with the increase in the dietary level (83-99%). Regression analysis revealed significant negative correlations between dietary HAS intake and HAS digestibility in both ileorectostomized rats (r=-0.761, p<0.0001) and normal rats (r=-0.853, p<0.0001). The difference in the digestibilities of HAS between ileorectostomized and normal rats suggested that 16-25% of the ingested HAS was degraded in the cecum and colon through bacterial fermentation. When HAS was the sole dietary carbohydrate source (65.5% of the total diet), 66.5% of the HAS ingested was digested in the small intestine, 16.4% was degraded in the cecum and colon, and 17.1% was excreted into the feces.

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Parathyroid hormone (PTH) is known to regulate calcium and phosphorus metabolism. PTH activates the PTH/PTH-related peptide (PTHrP) receptor which is widely distributed in kidney, bone and various other tissues, and increases the activity of adenylate cyclase and phospholipase C. Our previous study suggested a decreased response of PTH in the kidney of rats fed a high phosphorus diet (P level 1.5%) compared with that in rats fed a control diet (P level 0.5%). In the present study, expression of PTH/PTHrP receptor mRNA was investigated in rat kidney, since alteration of the PTH/PTHrP receptor is one of the reasons for down-regulation of PTH action. A high phosphorus diet induced an increased of PTH, but the urinary excretion of cyclic 3′5′-adenosine monophosphate (cAMP) /creatinine was significantly decreased and the serum 1α, 25 (OH) ₂D₃ level tended to decrease. PTH/PTHrP receptor mRNA expression in the kidneys of rats fed the high-phosphorus diet decreased significantly on the 21st day. These data suggest that the down-regulation of PTH is caused by a decrease in PTH/PTHrP receptor mRNA expression, and that PTH/PTHrP receptors are decreased.

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In our previous paper, we assessed the oxidative stability of olive, soybean and whale oils by the Rancimat method, which is based on the conductometric determination of volatile degradation products of oil heated at 120°C with aeration. In the present study, organic acid components of volatile degradation products of oxidized oil were analyzed to evaluate the contribution of each acid to conductivity. The volatile degradation products of olive, soybean and whale oils were collected in distilled water (referred to as collected water hereafter). Free fatty acids in the collected water were extracted with diethyl ether, and analyzed by preparative thin-layer chromatography and gas chromatography. Organic acids in the collected water were analyzed by high-performance liquid chromatography. Model experiments to determine the increase of conductivity of various organic and fatty acids were tested by the Rancimat method. Formic, propionic, iso-butyric, n-butyric and iso-valeric acids by HPLC analysis and myristic, palmitic, stearic, oleic, linoleic and α-linolenic acids by GLC analysis were identified in the volatile degradation products (collected water) obtained from oxidized soybean oil. Organic acid (formic, propionic, iso-butyric and iso-valeric acids) formation was found to begin within a few minutes before the rancid point (induction time) of each oil, and organic acid production (especially in whale oil) was rapid. The order of organic acid corltents in the collected water was iso-valeric acid>iso-butyric acid>propionic acid>formic acid. On the other hand, the amounts of acetic acid were lower. Iso-valeric acid showed a greater effect on the increased conductivity than propionic, iso-butyric and formic acids. Long-chain saturated and unsaturated fatty acids had no effect on the increased conductivity.

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The antioxidant and synergistic effects of a mixed tocopherol concentrate containing various antioxidative substances were assessed in cookies containing iron at a level of 200ppm employing a storage test at 40°C. Addition of coffee bean powder showed a strong antioxidant effect, reducing the peroxide level in the lipid fractian of the cookies during storage. Caffeic acid and rosemary powder were slightly less effective, and condensed phosphate had little effect. On the other hand, citric acid, citric acid isopropyl ester, L-ascorbyl palmitate, L-proline and lecithin showed no effect. When a mixed tocopherol concentrate was added, L-proline showed the strongest synergistic effect, and extensively suppressed the increase in the peroxide value. However, other substances had no effect or promoted oxidation.

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