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Utilization of 14C-tyrosine in brain and peripheral tissues of developmentally protein malnourished rats
M Miller1, J P Leahy, F McConville
1Worcester Foundation for Experimental Biology, Shrewsbury, MA 01545.
Insights
Developmental protein malnutrition in rats showed fewer changes in tyrosine utilization compared to essential amino acids. This study tracked 14C-tyrosine uptake in brain and tissues during early development.
Area of Science:
- Biochemistry
- Neuroscience
- Developmental Biology
Background:
- Developmental protein malnutrition significantly impacts nutrient utilization in brain and peripheral tissues.
- Previous studies highlighted alterations in essential amino acid metabolism (leucine, phenylalanine, tryptophan) under protein-deficient conditions.
Purpose of the Study:
- To investigate the effects of developmental protein malnutrition on the uptake and incorporation of the semi-essential amino acid 14C-tyrosine.
- To compare tyrosine utilization in brain and peripheral tissues of rats born to dams on low-protein versus normal-protein diets during early development.
Main Methods:
- Rats were born to dams fed either a low-protein (8% casein) or a normal-protein (25% casein) diet.
- Uptake and incorporation of 14C-tyrosine into brain and peripheral tissues were measured from birth to 21 days.
- Measurements were taken at various post-injection time points (10, 20, 90, 180 minutes) and developmental stages (birth, Day 5-21).
Main Results:
- At birth, low-protein pups showed decreased 14C-tyrosine incorporation at early time points (10, 20 min) but not later intervals.
- During development (Days 5-21), low-protein rats exhibited increased 14C-tyrosine uptake in brain and peripheral tissues by Day 11.
- Significantly higher incorporation of 14C-tyrosine into brain protein was observed in low-protein rats on Day 21, with minimal changes in peripheral tissues.
Conclusions:
- Developmental protein malnutrition affects tyrosine utilization less profoundly than essential amino acids.
- Tyrosine uptake and brain incorporation show developmental plasticity even under dietary protein restriction.
- These findings suggest a differential impact of protein malnutrition on amino acid metabolism during neurodevelopment.
Abstract:
Prior studies of developmentally protein malnourished rats have reported substantial changes in brain and peripheral utilization of 14C-leucine, 14C-phenylalanine, and 14C-tryptophan. In the present study rats born to dams fed a low protein diet (8% casein) compared to the offspring of control rats fed a normal diet (25% casein) showed few significant differences in the uptake and incorporation of 14C-tyrosine into brain and peripheral tissues from birth to age 21 days. At birth, the 8% casein pups exhibited significant decreases in brain and peripheral tissue incorporation of tracer only at short post-injection times (10 and 20 min), but not at longer intervals (90 and 180 min). During ontogenetic development (Days 5-21), the 8% casein rats showed significant increases in uptake of 14C-tyrosine into the brain and peripheral tissues on Day 11 and a significantly higher percent incorporation of tracer into brain protein on Day 21 as compared to the 25% casein rats. For the most part, there were no significant changes in incorporation of radioactivity in peripheral tissues for the 2 diet groups on these post-birth days. Overall, the data indicates that developmental protein malnutrition causes relatively fewer changes in brain and peripheral utilization of the semi-essential amino acid tyrosine than those observed in previous studies with essential amino acids.