INFLUENCE OF FOOD RESTRICTION AND COMPENSATORY GROWTH ON PROTEIN-SYNTHESIS AND BREAKDOWN IN GROWING RATS

The experiment was carried out with 24 male albino rats (5 weeks old, live weight 79 +/- 5.1 g) divided into 2 groups. Gr. 1 (control group) was fed the commercial breeding food Ssniff with 22.4% crude protein ad lib., Gr. 2 (test group) for the first fortnight a mixture of the b reeding food/cellulose 60/40 (restriction period) and subsequently for the second fortnight (compensatory period) also the breeding food ad lib. During both of these periods an 8 day N balance trial and a 4 day N-15 tracer trial were included for estimation of growth rate and pro tein synthesis rate. Protein synthesis was ascertained by the endprodu ct method (oral application, single dose, mixture of 12 N-15-labelled amino acids); protein breakdown was calculated as the difference of pr otein synthesis rate and growth rate. The estimated rates were convert ed into fractional ones by referring to the body N content of correspo nding animals. From the results of this experiment is concluded: The s maller N balance during moderate nutritional restriction can be attrib uted to a decrease of protein synthesis. The compensatory growth of th e animals during the realimentation period is caused by an increase of protein synthesis and the enhanced protein conversion. Protein degrad ation is nearly unaffected.