Effect of zinc level in the refeeding diet in previously starved rats on plasma somatomedin C levels.

White male growing rats were fed rat chow diet for 4 days after which they were fasted for 72 h. At the end of fasting, rats were allotted into four dietary treatments that varied only in the level of zinc (Zn): Zn-deficient group (ZnD), 30, 90, and 140 ppm of Zn. A group of eight rats were not fasted and were fed the rat chow diet throughout the experimental period. Blood was obtained at intervals from all groups for the measurements of Zn and somatomedin C (SMC) in the plasma. Eight rats were randomly selected at zero time (t0) and at the end of fasting period were killed for the measurement of tibia Zn. At the end of refeeding, all rats were killed for tibia Zn determination as well. Results showed that plasma SMC decreased to the hypopituitary level at the 3rd day of fasting. At 48 and 72 h of refeeding, the levels of plasma SMC increased significantly in all experimental groups and the differences among groups were not significant. The levels of SMC in groups fed 140 and 90 ppm of Zn continued to increase significantly with progressive refeeding. However, in groups fed 30 ppm and ZnD diets the levels of SMC started to decline after 72 h of refeeding. The levels of plasma Zn followed similar trend as SMC levels. In addition, the levels of Zn in the tibia were comparable in all groups with SMC and plasma Zn levels at the end of fasting or refeeding period. Previous reports showed that plasma SMC level is a more reliable index used to monitor nutritional responses; thus, it could be concluded that the level of Zn in the diet should be considered carefully when planning nutritional intervention for severe malnutrition or starvation.