EFFECT OF ZINC-DEFICIENCY ON THE WEIGHT, CELLULARITY AND ZINC CONCENTRATION OF DIFFERENT SKELETAL-MUSCLES IN THE POST-WEANLING RAT

Zinc-deficient (ZD), weight-restricted (WR), pair-fed (PF) and ad lib. -fed (AL) Sprague-Dawley male rats were killed after feeding the respective Zn-deficient and Zn-supplemented diets from 3 to 8 weeks of age. Animals killed at the start of the experiment served as a baseline control (BC). Four different skeletal muscles – biceps brachii, soleus, plantaris and extensor digitorum longus (EDL) – were studied for changes in weight, the number and diameter of muscle fibres and Zn concentration. The soleus muscle had the highest concentration of Zn. It was the only muscle to reduce its Zn concentration due to Zn deficiency. There was a loss of muscle fibres during normal growth (groups BC v. AL) in the soleus muscle (P < 0.05). The estimated length of muscle and the diameter of the muscle fibres in all four muscles increased significantly (P < 0.001). Therefore postweanling growth appears to occur as a result of longitudinal and transverse increases in the dimensions of these muscles. The reduction in muscle fibre number in ZD rats compared to BC animals may occur within the range of expected fibre loss during normal growth. Fibre loss in ZD rats may be more affected by feeding-pattern-dependent metabolic changes than by a deficiency of Zn per se (groups ZD v. WR). Soleus fibre loss in ZD rats may be related to the high Zn concentration in this muscle. The effect of Zn deficiency per se on muscle fibre diameter may be inaccurately interpreted by comparing the ZD animals with their PF and AL controls. There was no significant difference in fibre diameter in any of the four muscles when ZD and WF rats were compared. © 1979, The Nutrition Society. All rights reserved.