TY  - JOUR
PY  - 1989//
TI  - Effects of a vitamin-A-free diet on tissue vitamin A concentration and dark adaptation of aging rats
JO  - Experimental gerontology
A1  - Bankson, D. D.
A1  - Ellis, J. K.
A1  - Russell, R. M.
SP  - 127
EP  - 136
VL  - 24
IS  - 2
N2  - Changes in serum, hepatic, and ocular vitamin A levels were followed in 9-month-old Long Evans rats fed either a vitamin-A-free or vitamin-A-sufficient diet for up to 18 months. After 18 months, hepatic total vitamin A fell exponentially from 2542 +/- 433 to 48 +/- 12 micrograms/g wet weight, but these stores maintained normal serum retinol and ocular total vitamin A concentrations in vitamin-A-deprived rats. However, retinal dark-adaptation time, a functional indicator of photoreceptor integrity, was prolonged in elderly vitamin-A-deprived rats as compared to vitamin-A-sufficient controls (p less than 0.05). Aging appeared to be the most important factor that depressed the rate of dark adaptation, with vitamin A status having a secondary effect. The proportion of total ocular retinaldehyde decreased (p less than 0.05) and the concentration of retinyl ester increased (p less than 0.05) in the eyes of 27-month-old vitamin-A-deprived rats compared to age-matched vitamin-A-sufficient animals. Possible mechanisms of visual dysfunction include abnormal retinal rhodopsin recycling caused by a dependence on newly absorbed dietary vitamin A (e.g., chylomicron). Alternatively, in the vitamin-A-deprived rat, decreased hepatic oxidation of pentobarbital (used for electroretinographic anesthesia) could prolong retinal anesthetic exposure and either directly depress neural transmission or indirectly alter transmission by affecting rhodopsin recycling.<p /> <p>Language: en</p>
LA  - en
SN  - 0531-5565
UR  - http://dx.doi.org/
ID  - ref1
ER  -