The Effect of Testosterone, Nandrolone and Their Combination on the Structure and Ultrastructure of Muscle Fibres and Myofibrils in Pigs

There is increasing pressure on meat producers worldwide due to the need for higher yields and improved meat quality. This is why anabolic androgenic steroids (AAS) have been widely used in most countries, due to their ability to accelerate animal muscle growth. However, out of concern for their side effects, EU states have banned their use and implemented control mechanisms. But they are reaching their limits, and therefore, it is necessary to look for new ways and investigate the mechanism of action of AAS on muscle tissue. This study replicated the administration of banned AAS (testosterone, nandrolone and their combination) and observed their effect on pig muscle. The pig model was purposely chosen for the study, as no such research has been carried out on this species. At the same time, pork is one of the most consumed meats in Europe. It focused on histological changes in muscle structure, specifically the size of muscle fibres and the number of satellite cells per muscle fibre. Furthermore, ultrastructural changes in muscle fibres, the diameter of myofibrils, the number of myofibrils per area, the distance between myofibrils and the size of sarcomeres were examined. The results using the techniques of histology, fluorescent labelling and transmission electron microscopy showed that, after the application of AAS, there is an increase in the diameter of muscle fibres, an increase in the diameter of myofibrils, a decrease in the number of myofibrils per surface area and, in the case of testosterone, an increase in the distance between myofibrils and an increase in the length of sarcomeres. There was also a significant increase in the number of satellite cells per muscle fibre. The detected statistically significant differences between control and experimental groups provide evidence that selected histological parameters could be additional mechanisms for detecting the presence of AAS in pork meat in the future.