Effects of muscle type, castration, age and growth rate on H-FABP expression in bovine skeletal muscle

Heart fatty acid-binding protein (H-FABP) supplies long-chain fatty acids (LCFAs) as an important energy source for muscle growth and maintenance, and also directs LCFAs towards fat storage within muscle fibres. We show the results of two independent experiments to characterise the variability of (a) H-FABP protein content, and (b) H-FABP mRNA level in various bovine muscles. The H-FABP protein content in Belgian Blue bulls was positively correlated with the oxidative potential of the muscle. The regulation of H-FABP mRNA expression by breeding factors was studied in Montbeliard cattle. Thirty bulls and 30 steers were assigned to four different slaughter age groups (4, 8, 12 and 16 months-of-age). Four or five animals of each sex were slaughtered at each age. At 8 months, bulls and steers were divided into groups of either restricted (R) or ad libitum (AL) access to feed. To induce compensatory growth (C), remaining R animals were allowed ad libitum access to feed between 12 and 16 months-of-age, as were remaining AL animals. Total RNA was extracted from muscle samples taken at slaughter, i.e. m. semitendinosus (ST; glycolytic), m. triceps brachii (TB; mixed) and m. splenius (SP; oxidative). Equal amounts of total RNA (20 mug) were assayed for H-FABP mRNA levels by Northern hybridisation. At any age investigated, H-FABP mRNA levels per total RNA unit were higher in SP than in ST (P < 0.01), as much as 3.5-fold at 16 months-of-age. In each muscle, although at different ages, H-FABP mRNA levels increased approximately two-fold (P < 0.05) with increasing age. Castration had no effect on H-FABP mRNA expression. H-FABP mRNA levels were lower (P < 0.61) in ST of R than AL or C animals. In conclusion, the H-FABP mRNA and protein levels are potentially good indicators of the muscle metabolic type at a given age. In bovine skeletal muscle, however, H-FABP mRNA expression was little affected by the nutritional level and not regulated by testicular steroids. (C) 2002 Elsevier Science B.V. All rights reserved.