Title ofthe paper: <b>Growth of skeletal muscle and IGF-I in pigs of different sex</b><br> IGF-I is a pluripotent factor that is involved in regulation of growth, differentiation and a large number of functions in numerous tissues and their cells. IGF-I is synthesized by hepatocytes (endocrine role) and several extrahepatic tissues (e.g. skeletal muscle; autoerine and paracrine role). In our study, we describe the postnatal growth of the skeletal muscles in pigs of various sex taking into

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... t the possible influence of endogenous IGF-I. <br><br> The investigation was made on 42 crossbred pigs. Seven blood samples and 4 biopsy samples of two muscles (<i>M. longissimus dorsi</i> and <i>M. triceps brachii</i>) were taken for the determination of IGF-I blood plasma concentration and muscle fibre diameter, respectively as well as for further muscle structural and biochemical traits. IGF-I plasma concentrations show an increase during fattening with significantly highest levels for boars. Phenotypic differences between sows and boars in thickness of Shoulder muscle are proven after the day 181 with ultrasonography because significant differences were detected in mean muscle area of <i>caput longum musculi triceps brachii</i> between sows and boars and barrows (180th day of life). There are no significant differences in mean muscle fibre diameter of both muscles between sexes. A group of animals with high mean diameter in muscle fibres (day 200) of <i>M. triceps brachii</i> has significantly higher IGF-I concentrations in blood plasma than a group of animals with low muscle fibre diameter in the same muscle.