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Human Nutrition Research Center, U.S. Department of Agriculture, Boston, MA 02111
The effect of protein energy mainutrition (PEM) on retinal function was investigated in weanling Long-Evans rats fed a low protein (4.2%) diet. After 8 wk, plasma retinol levels were lower in low protein (LP) and growth-restricted (GR) groups than in ad libitum controls (P < 0.05); however, ocular vitamin A concentration remained normal. Plasma taurine concentration was lower only in the LP group, while retinal taurine was lower in both LP and GR groups than in control groups. The dark-adapted electroretinogram (ERG) became abnormal (e.g., depressed a and b waves, P < 0.05) in both LP and GR groups but was corrected by ad libitum feeding of the control diet for an additional 8 wk. In a second study, weanling LP rats were supplemented with 0.4% taurine, 0.4% methionine or 0.4% glycine. Although taurine supplementation maintained plasma and retinal taurine stores, ERGs remained abnormal with retinal sensitivity significantly lower than in unsupplemented LP rats. Thus, PEM produced abnormal ERGs independent of ocular vitamin A concentration and retinal taurine levels. The high dietary taurine fed to protein-malnourished rats caused further impairment of visual function but was not detrimental to control or pair-fed rats.
KEY WORDS: protein energy malnutrition taurine retina vitamin A visual function
1 Supported by U.S. Department of Agriculture Grant No. K53-3K06-5-10.
2 Presented in part at the 1985 meetings of the American Society for Clinical Nutrition in Washington, DC, and the Association for Research in Vision and Ophthalmology in Sarasota, FL.
3 Present Address: Department of Pathology and Hospital Laboratories, Division of Clinical Chemistry, 1071 PST, University North Carolina, Chapel Hill, NC 27514.
4 To whom reprint requests should be sent.
Manuscript received 3 September 1987. Revision accepted 22 September 1987.