The rickets-producing and anti-calcifying action of phytate / by Edward Mellanby.

  • Mellanby, Edward, Sir, 1884-1955.
Date:
[1949?]
Catalogue details

Licence: In copyright

Credit: The rickets-producing and anti-calcifying action of phytate / by Edward Mellanby. Source: Wellcome Collection.

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    experiments which were made to compare the effects of sodium phytate and inorganic phosphate, the latter was prepared from sodium phytate by hydrolysis with yeast (p. 2). A solution of sodium phytate was mixed with a suspension of baker’s yeast (25 mg. of P to 1 g. of yeast), the pH was corrected to 4-5 and the mixture was incubated at 45° C. for 12 hr. with constant stirring. At the end of this period the solution was boiled for 5 min., cooled, and the HC1 was neutralized with NaOH. This treatment converted all the phytate to inorganic phosphate. As controls similar solutions and suspensions of Na phytate and yeast were incubated separately as above. The yeast was boiled and when cool was added to the phytate solution, the HC1 being neutralized as before. This mixture contained the same amount of P as the previous one, but in the form of phytate, with only a trace of inorganic P. Preparation of calcium phytate {Exp. 10). 4000 ml. of a solution containing 5 mg. of P per ml. as sodium phytate were brought to pH 5-5 with HC1. 1000 ml. of 6% CaCl2 solution, also at pH 5-5, were added. After being stirred briskly for a few minutes the mass was filtered on a Buchner funnel, washed with a small quantity of water and then with 80 or 90 % alcohol. The Ca phytate was then spread out to dry at room temperature and the Ca, total P and phytate P estimated. Assessment of results The methods of assessing the experimental results included: (1) X-ray examinations, (2) the estimation of the A/R ratios* and (3) a study of the mineral metabolism balances. In general these findings were supported by the appearance of the animals and the histological examination of the bones. As regards the X-ray appearances, an attempt has been made to number the stages of rickets from 1 to 10, but it must be pointed out that these numbers, although relative, do not represent absolute degrees. During life the diagnosis was made from X-rays of the left forepaw only, but post-mortem the appearance of the ribs and other bones was considered. The method of marking and collecting faecal and urine samples is given on p. 494. The collected faecal samples were heated to 100° C. within 9 hr. of collection, dried, weighed, ground and stored for future analysis of Ca, phytate P and total P. The methods used in the analysis were: Estimation of phytate phosphorus in foods, faeces and urine was carried out by the method of McCance & Widdowson (1935), with slight modifications, including an increase in the concentration of the ferric chloride solution. Total phosphorus in foods, faeces and urine was estimated by the method of McCance & Wid¬ dowson (1935). Inorganic phosphorus and the total and phytate phosphorus after incineration were estimated colorimetrically by various methods, including those of Briggs (1922), Fiske & Subarrow (1925), and Allen (1940). For the final comparisons a Spekker photoelectric absorptiometer was used. Calcium in foods, faeces and urine was estimated by various methods, principally those used by Macy (1942), McCance & Widdowson (1942a), and for foodstuffs, the Imperial Bureau of Animal Nutrition (1937). RESULTS The relative effect of phytate and phosphate with varying bodily vitamin D reserves The litters used in these experiments received different amounts of vitamin D during the pre-experimental period. When good supplies were given to the mothers during pregnancy and lactation and to the puppies individually during and after weaning, the body reserves of the vitamin at the beginning of the experimental period would be high. When, however, the puppies had no sup¬ plies of the vitamin in this period, their reserves would be lower.