Dietary protein quality and zinc levels in growing rats.

摘要

Previously, a low protein diet has been shown to cause thymus atrophy which was also associated with Zn deficiency in growing rats. The aim of this study was to determine if the intake of this low protein diet induced a concomitant Zn deficiency. Rats of the Wistar strain were fed from weaning and during 10 days a 6.5% maize protein diet (M10) or a 6.5% casein diet (C10). An age-matched control group was run simultaneously (C). The only dietary variable was the protein quality, the Zn content beingthe same. Food intake (g/day) was similar: (M10: 6.5±1.4, C10: 6.8±1.1). Zn levels were determined by atomic absorption spectrophotometry in plasma (P), whole blood (WB), liver (L) and thymus (T) and expressed asμg/ml andμg/g wet tissue, respectively.No differences were found in WB (M10: 3.85±0.24, C10: 3.88±1.00, C: 3.67±0.34) nor L (M10: 42.50±11.30, C10: 36.30±6.70, C: 39.10±8.60). However, P levels decreased in M10 and C10 when compared to C (M10: 1.84±0.63, C10: 1.79±0.41, C: 2.43±0.37, P<0.04)while a significant increase in thymus Zn was only found in M10 compared to C10 and C (M10: 40.00±13.20, C10: 26.50±2.70, C: 27.10±3.60, P<0.01). These results show that the intake of a low quality dietary protein might alter the distribution of plasmaZn with a concomitant uptake of Zn by the thymus.