R. F. Krause

Influence of vitamin A on cholesterol blood levels.

Summary Oral administration of 100,000 I. U. of Vit. A acetate for 4 to 6 months significantly reduced the elevated serum cholesterol levels in atherosclerotic patients but had no effect on individuals with normal cholesterol levels.

The effect of retinol and retinoic acid on physiological and biochemical changes in retinol-deficient rats

1. The effects of retinol and retinoic acid supplementation of retinol-deficient rats were studied for a variety of metabolic processes shown to be affected by retinol-deficiency. 2. Retinol-deficient rats were found to have decreased body-weight, liver and testes weights, a degeneration of testicular germinal cells, an increased incorporation of labelled choline into liver and testes phospholipids, an increased protein synthetic activity (in vitro) of liver ribosomes, an increased transfer-RNA methyltransferase activity in liver and a decreased activity in testes, an increased DNA content of testicular nuclei, and a decreased uptake of [3-H]thymidine by testicular nuclear DNA. 3. In retinol-deficient rats supplemented for 8 weeks with retinol these changes were reversed, measurements returning to control levels. 4. In retinol-deficient rats supplemented for 8 weeks with retinoic acid all changes were reversed except those in the testes. 5. Testicular signs of retinol deficiency appeared to be delayed when retinoic acid was added to the retinol-deficient diet of weanling rats. This suggests a sparing action of retinoic acid on the rats utilization of retinol. 6. Suggestions are offered as to why retinoic acid will support growth and development but not spermatogenesis in the rat.

Effect of Vitamin A Deficiency on the Protein Synthetic Activity of Rat Liver Ribosomes

Summary Vitamin A deficiency enhances the in vitro capacity of rat liver ribosomes to make protein. This stimulatory effect of vitamin A deficiency on protein synthesis is due to the pH 5.1 enzyme fraction.

Asymmetrical Incorporation of C14 Acetate into β-Carotene Biosynthesized by Phycomyces blakesleeanus.

Summary β-carotene biosynthesized by Phycomyces blakesleeanus was purified by column chromatography over basic silicic acid. Degradation studies on the ring system of this radioactive β-carotene indicate that the carboxyl carbon of acetate is incorporated into positions 1, 1′, 3, 3′, 5 and 5′ of the ring system whereas the methyl carbon is incorporated into all positions of the ring system. Our studies also indicate that the ring carbons are more radioactive than the side chain carbon atoms.

Serum Cholesterol Determinations as Affected by Vitamin A

Summary 1. A study was made of the effects of various levels of Vit. A in the serum on total cholesterol as determined by a method using a ferric chloride color reagent and a saponification-extraction method. 2. Comparison between the 2 methods showed that the Vit. A must be separated from the serum before making total cholesterol determinations by the ferric chloride color reagent method.

Phosphonolipid Metabolism in Control and Vitamin A Deficient Rats

Summary The rate of incorporation of labeled 2-aminoethylphosphonate (AEP) into liver lipids was similar for microsomes, mitochondria and soluble fraction. In vitamin A deficiency this rate was accelerated in all subcellular fractions. The peak of incorporation was between 3 and 6 hr. The half-lives of lipid labeled with AEP from microsomes, mitochondria and soluble fractions were statistically similar (approx 4 days) for control and deficient rats. The authors thank Dr. John M. Krall, Assistant Professor of Medicine, Public Health and Preventive Medicine, West Virginia University for his assistance in the statistical treatment of our data.

Metabolism of C14 Labelled Beta-Carotene in the Rat.∗

Summary Feeding of C14 labelled carotene resulted in the deposition of approximately 1.5% of absorbed C14 into liver vit. A. In the total animal an average of about 15% of the absorbed C14 went into fatty acids, and 40% into non-saponifiable material. An average of about 5% of the absorbed C14 was found in the expired CO2. Approximately 40% of the absorbed C14 remains to be accounted for.

Conversion of C14 carotene to a non-saponifiable substance or substances in the rat.

Summary The feeding of C14 labelled carotene resulted in the deposition of all of the absorbed C14 in the carotene-free, non-saponifiable fraction from the total animal. The highest concentration of C14 was found in the extrahepato-intestinal tissues, and the least amount was recovered in the liver.

Metabolism of β-Carotene.

Summary Evidence has been presented through the use of doubly-labeled β-carotene and singly-labeled retinol that β-carotene is converted to product(s) other than retinol.

In vitro Metabolism of C-14 Labeled β-Carotene.∗:

Summary Ten to 20% of β-carotene was destroyed by incubating C-14 labeled β-carotene with various tissues from the rat. All tissues studied had the ability to transfer radioactivity from β-carotene to sterols, saponifiable material and steam-distillable compound or compounds. ATP, DPN, nicotinamide and MgCl2 were cofactors that increased β-carotene destruction by cell-free homogenates. A negligible amount of CO2 was liberated during incubation. The author thanks Mrs. Phyllis Spiker for technical assistance.