The effects of riboflavin derivatives on the heart of open-chest dogs and the atrium isolated from guinea pigs were studied. FMN and DBRP did not show a marked effect on both preparations. In the dog preparation, FAD decreased the myocardial contractile force which was finally increased, prolonged PQ, QRS, QT and RR intervals, and decreased the blood pressure. The duration of the action of FAD was about five minutes. In the isolated atrium, FAD decreased the amplitude of contraction, DNRP showed the negative inatropic action on the dog heart, prolonged intervals of PQ, QRS, QT and RR, and the hypotension. DNRP, in higher doses, decreased the amplitude of contraction of the atrium. The action of TNR was similar to that of DNRP.

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Decomposition of thiamine by Cu^<2+> under ordinary cooking conditions at the neutral range was investigated and it was found that the decomposition was affected by the initial concentration of thiamine, heating time and temperature, pH and kinds of buffers. The decomposition was accelerated especially by the presence of Cu^<2+> even at 0.02 ppm, as compared with other metal ions. Increase of TDS (thiamine disulfide) formation was accompanied with concentration of Cu^<2+>, pH, heating time and temperature. The main decomposition products of thiamine by Cu^<2+> at the neutral range were identified as OMP^<*1)>, Th^<*2)>, Thc^<*3)>, TDS^<*4)> and SB_1^<*5)> by means of paper chromatography. There was much more difference between the contents of TDS and Thc, when thiamine solution was heated with or without Cu^<2+>.

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The biological activities of nine kinds of tocopheryl esters were studied by the hemolysis test using dialuric acid. By the test of oral administration, the activities of dl-α-tocopheryl acetate, d1-α-tocopheryl nicotinate, d1-α-tocopheryl glycolate, d1-α-tocopheryl linoleate, d1-α-tocopheryl dihydroxyacetate and d1-α-tocopheryl acid succinate were found to be between 85% and 100% of that of d1-α-tocopherol while the activities of dl-α-tocopheryl phosphoacetate and d-γ-tocopheryl acetate were 25% and 15% of that of d1-α-tocopherol. By the test of intraperitoneal administration, d1-α-tocopheryl glycolate, d1-α-tocopheryl phosphoacetate and d1-α-tocopheryl dihydroxyacetate were found to be as active as d1-α-tocopherol, while the activities of d1-α-tocopheryl acetate, d1-α-tocopheryl nicotinate, d1-α-tocopheryl linoleate and d1-α-tocopheryl acid succinate were corresponding to a half of that of d1-α-tocopherol. The activities of d-α-tocopheryl acid succinate and d-γ-tocopheryl acetate were 70% and 10% of that of d1-α-tocopherol respectively. It was assumed that these differences in the activities of tocopheryl esters might be related to differences in hydrolysis in tissues as well as speed of absorption from the gut.

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The lipid content, especially sterols and phospholipids which are the major components of biological membrane, of liver and intestinal mucosa was investigated in vitamin D deficient and normal rats. Total lipid content was increased in vitamin D deficient rat liver, and this increased lipid content was lowered to normal level by an oral administration of 2,000 IU vitamin D_3. No significant change between vitamin D deficient and normal rats on serum cholesterol and the phospholipid content in both liver and intestinal mucosa was observed. Vitamin D deficiency caused a decrease of FAS (fast acting sterols, mainly composed of cholesterol precursors) and a slight decrease of SAS (slow acting sterols, mainly cholesterol). In liver, vitamin D_3 treatment resulted in an increase of FAS after 3 hours. On the other hand, further decrease of FAS was shown in an intestinal mucosa by vitamin D_3 administration. These results suggest that vitamin D affects the sterol metabolism as well as calcium metabolism.

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