Cellular and molecular regulation of muscle growth and development in meat animals

¹ Department of Animal Science, University of Minnesota, St. Paul, 55108

^* To whom correspondence should be addressed. E-mail: wdayton{at}umn.edu.

	Abstract

Although in vivo and in vitro studies have established that anabolic steroids, transforming growth factor- (TGF-), and myostatin affect muscle growth in meat-producing animals, their mechanisms of action are not completely understood. Anabolic steroids have been widely used as growth promoters in feedlot cattle for over 50 yr. A growing body of evidence suggests that increased muscle levels of IGF-I and increased muscle satellite cell numbers play a role in anabolic steroid enhanced muscle growth. In contrast to anabolic steroids, the members of the TGF-/myostatin family suppress muscle growth in vivo and suppress both proliferation and differentiation of cultured myogenic cells. Recent evidence suggests that IGFBP-3 and -5 play a role in mediating the proliferation-suppressing actions of both TGF- and myostatin on cultured myogenic cells. Consequently, this review will focus on the roles of IGF-I and IGFBP in the cellular and molecular mechanisms of action of anabolic steroids and TGF-/myostatin, respectively.

Key Words: muscle, Anabolic steroid, Myostatin, Insulin-like growth factor-I, Insulin-like growth factor binding protein, Transforming growth factor-beta