H. Steenbock

The role of vitamin D and intestinal phytase in the prevention of rickets in rats on cereal diets.

Abstract A study with rats of the role played by vitamin D in overcoming the rachitogenic properties of high-Ca phytic acid containing diets has shown that phytic acid in a low-Ca cereal ration was hydrolyzed almost completely even when vitamin D was absent. On the other hand, when the Ca content of the ration was increased, the hydrolysis of phytate was decreased. Under these conditions the addition of vitamin D increased the hydrolysis. The phytase and alkaline phosphatase activity of fecal and intestinal extracts from rats, whether they were fed cereal or noncereal, rachitogenic or nonrachitogenic rations, was always increased when vitamin D was given. However, no consistent correlation in a quantitative sense was found between the degree of hydrolysis of dietary phytate and enzyme activity, nor with the severity of rickets. The increased hydrolysis of phytic acid which is effected by the addition of vitamin D to high-Ca cereal diets did not liberate sufficient P in the inorganic form to account by itself for the prevention of rickets. Although less phytate was hydrolyzed by rachitic rats, the inorganic P in the feces was increased due to a decrease in its absorption. It therefore appears that the antirachitic action of vitamin D with cereal diets is due primarily to an improved utilization of inorganic P.

Vitamin D and the structure of kidney mitochondria.

Abstract An electron microscopic examination has been made of thin sections of kidney mitochondria isolated in 0.44 M sucrose from vitamin D deficient rats and from vitamin D treated rats. Vitamin D deficiency resulted in swollen and morphologically damaged mitochondria characterized by large intercristal spaces and disrupted cristal systems. These changes were prevented by vitamin D.

The effect of vitamin D on urinary citrate in relation to calcium, phosphorus and urinary pH.

Abstract Vitamin D increased the amount of urinary citrate excreted by young rats kept on rations varying widely in mineral content. These rations ranged in composition from those providing an adequate mineral intake to those made grossly deficient in Ca, P, and other minerals. The biggest percentage increase in citrate was obtained with P-containing rations, but supplements of P, given in the form of neutral solutions of K phosphates to a low-P ration, reduced citrate elimination. An increase in urinary pH induced by vitamin D with rats on low-P rachitogenic rations was not obtained with rations adequate in P, yet an increase in citrate elimination resulted in all instances. Inasmuch as a supplement of vitamin D increased urinary citrate far more than did an additional large intake of NaHCO 3 , it appears that the effect of vitamin D is due to an increase in citrate synthesis rather than to a decrease in its destruction.

Calcium metabolism and growth in the rat on a low-phosphorus diet as affected by vitamin D and increases in calcium intake.

Abstract Studies with young rats on low-P, vitamin D-containing diets, with various levels of CaCO 3 as the source of Ca, revealed that the negative Ca balance induced by a low-P diet can be changed to a positive one by increasing the Ca intake. This was not possible when the diet did not contain vitamin D. With the afore-mentioned retention of Ca, growth was decreased while the Ca content of the blood and the amount and percentage of ash in bone were increased. This improvement in calcification supports the theory that the decrease in growth induced by the addition of vitamin D to this ration was effected by a differential shunting of P from the metabolic pool to bone instead of to soft tissues. Analysis of the urines revealed a definite limitation in the capacity of the kidneys to excrete Ca, which capacity was not affected by vitamin D. Ca in the feces was reduced by vitamin D at all levels of Ca intake.

A rachitogenic and growth-promoting effect of citrate☆

Abstract In studies with rats it was found that the absorption of Ca from a vitamin D-free diet which contained adequate amounts of Ca (0.5%) and a low supply of P (0.015%) was greatly reduced by the incorporation of Na citrate and citric acid. When vitamin D was added, in addition to the citrate, the absorption of Ca was increased but the level attained was still lower than when citrate was omitted. It is concluded from observed negative Ca and P balances, decreases in bone ash, and increases in metaphyseal widths that citrate had a rachitogenic effect.

Crystallization at low temperatures as a technique in the analysis of oils

Summary1. A rapid method for determining the saturated, oleic, linoleic and linolenic acids in a 1-gram sample of fat has been described.2. Saturated fatty acids were separated by quantitative crystallization from acetone solution at −40° C.3. The three unsaturated acids, oleic, linoleic and linolenic, were calculated from the iodine and thiocyanogen values of the remaining liquid acids.4. Analysis of known mixtures of fatty acids demonstrated the accuracy of the method to be approximately ±2 units percent.5. Duplicate determinations of the fatty acid distribution in natural oils agreed within 0 to 4 units percent.6. Data on the oleic, linoleic, and linolenic acid content of 15 seed oils were presented.

Vitamin D and Urinary Amino Acid Excretion in the Rat.

Summary Free alpha amino nitrogen as well as individual amino acids have been determined in urine of rats fed various diets with and without Vit. D. In contrast to infantile rickets, no aminoaciduria occurs in Vit. D deficiency whether strongly rachitogenic or non-rachitogenic diets are fed. Furthermore, a rachitogenic casein diet also produced no aminoaciduria.

The effect of a vitamin D-free fat on the absorption and retention of phosphorus.

Abstract A vitamin D-free fat, namely, purified cottonseed oil, incorporated in an adequate-calcium, low-phosphorus, cereal-free rachitogenic ration, when fed to young rats increased the absorption and retention of phosphorus but decreased the percentage of bone ash. This apparently was caused by an increase in growth which made the demand for phosphorus of certain soft tissues dominant over those of bone. When fat was fed with the basal ration supplemented with an adequate amount of phosphorus, the demand of both types of tissue could be met; calcification of bone was increased and the phosphorus content of certain soft tissues such as the liver was also increased. It follows, that data on calcification of bone cannot always be used as a criterion of the over-all state of phosphorus equilibrium in the animal.