Vitamin a Requirements of Animal Species

Rubin, Saul H.; Ritter, E. De

doi:10.1016/s0083-6729(08)61010-9

Cited by 14 publications

(3 citation statements)

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“…Administration of thyroxine or thyroid preparations (60) improves carotene absorption; thiouracil inhibits it. The evidence supports a /3-carotene to vitamin A weight ratio of 2:1 (185) for low levels of /3-carotene supplementation of the rat's diet. When carotene is fed at levels sufficient to elicit liver stores of vitamin A, the relative efficiency of conversion to and storage as vitamin A is markedly reduced (10,111,150,156,158).…”

Section: Rat Studiesmentioning

confidence: 62%

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Carotenoid vitamin A precursors and analogs in foods and feeds

Bauernfeind¹

1972

J. Agric. Food Chem.

215

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Section: Rat Studiesmentioning

confidence: 62%

“…It is apparent that /3-carotene is best utilized at quite low levels in the ration (22,185). A fairly well developed mechanism, in the absence of deterrents, exists to convert limited dietary intakes of /3-carotene to the necessary vitamin A.…”

Section: Factors Influencing Activitymentioning

confidence: 99%

Carotenoid vitamin A precursors and analogs in foods and feeds

Bauernfeind¹

1972

J. Agric. Food Chem.

215

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“…retinyl palmitate (ICN Life Sciences Group, Cleveland, Ohio); this is approx¬ imately 7 times the reported retinol requirement for the rat (Rubin & De Ritter, 1954;Moore, 1967b;Ahluwalia & Bieri, 1970) but is considerably below toxic levels (Nieman & Obbink, 1954). Treatment with the special diet was initiated at 27 days of age and continued until approximately 9 months of age.…”

Section: Methodsmentioning

confidence: 99%

Inhibition of cyclic ovarian activity in rats treated chronically with vitamin A

Rj¹

1977

Reproduction

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The effects of altering the dietary level of vitamin A on cyclic ovarian activity, and serum and hepatic vitamin A concentrations were studied in female rats. High but non-toxic oral doses of retinyl palmitate (5000 i.u., 3 times/week) significantly advanced the age at vaginal opening but had no effect on vaginal and ovarian cycles after 15 weeks of treatment. Hepatic stores of vitamin A were significantly elevated but serum levels were unchanged. Retinol-deficient rats given a supplement of retinoic acid had a normal vaginal opening age but displayed cornified vaginal cells for many of the days that smears were taken. Hepatic and serum vitamin A concentrations were markedly reduced. When treatment with high doses of retinyl palmitate was continued for 9 months, animals developed polycystic anovulatory ovaries which were significantly lighter than those of controls. Retinol-deficient rats given retinoic acid and demonstrating depleted hepatic vitamin A reserves had ovaries of normal weight and containing corpora lutea, indicating that retinol is not necessary for ovulatory activity. Short-term treatment (16 days) of rats with toxic doses of retinyl palmitate (50,000 i.u. daily) sufficient to raise serum and hepatic retinol levels significantly did not alter ovarian cyclicity; corpora lutea were present and ovarian weight was normal.These data indicate that long-term treatment with high but non-toxic doses of vitamin A inhibits cyclic ovulatory activity, perhaps via alteration of a steroidogenic mechanism in the ovary or adrenal since other studies indirectly support the existence of such a relationship. Furthermore, retinoic acid is a sufficient form of vitamin A replacement to maintain cyclic ovarian activity.

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