Growth of skeletal muscle and IGF-I in pigs of different sex

IGF-I is a pluripotent factor that is involved in regulation of growth, dif ferentiation and a large number of functions in numerous tissues and their cells. IGF-I is synthesized by hepatocytes (endocrine role) and several ext rahepatic tissues (e.g. skeletal muscle; autocrine and paracrine role). In our study, we describe the postnatal growth of the skeletal muscles in pigs of various sex taking into account the possible influence of endogenous IG F-I. The investigation was made on 42 crossbred pigs. Seven blood samples and 4 biopsy samples of two muscles (M. longissimus dorsi and M. triceps brachii) were taken for the determination of IGF-I blood plasma concentration and m uscle fibre diameter, respectively as well as for further muscle structural and biochemical traits. IGF-I plasma concentrations show an increase durin g fattening with significantly highest levels for boars. Phenotypic differe nces between sows and boars in thickness of shoulder muscle are proven afte r the day 181 with ultrasonography because significant differences were det ected in mean muscle area of caput longum musculi triceps brachii between s ows and boars and barrows (180th day of life). There are no significant dif ferences in mean muscle fibre diameter of both muscles between sexes. A gro up of animals with high mean diameter in muscle fibres (day 200) of M. tric eps brachii has significantly higher IGF-I concentrations in blood plasma t han a group of animals with low muscle fibre diameter in the same muscle.