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Satellite cells were isolated from the pectoralis major (PM) and biceps femoris (BF) muscles of 5-week-old broiler chickens to compare growth and differentiation characteristics in vitro. BF cells proliferated at greater rates in the growth medium and were more responsive to the mitogenic effects of chicken serum than PM cells at all levels tested (p < or = 0.05). When low serum-containing medium was administered, the levels of creatine kinase, a marker of differentiation, increased at greater rates in PM cultures than in BF cultures (p < or = 0.05). Administration of increasing levels of fibroblast growth factor in serum-free medium resulted in similar responsiveness of the two lines to this mitogen. No differences were detected in rates of protein synthesis or degradation in myotube cultures from the two muscle sources. The results suggest that satellite cells derived from PM and BF muscles of the chicken have different responsiveness to serum mitogens.

Myogenic satellite cell clones were established from the pectoralis major muscle of chickens with the low score normal (LSN) muscle weakness and controls. The percentage of cells which attached to substrata and began to proliferate was higher for the control line than the LSN line (55% vs 30%). Furthermore, of those clones which initiated growth, 63% of the control cells and only 32% of the LSN cells proliferated to confluence in 25 cm2 tissue culture flasks. Proliferation rates were significantly lower with LSN satellite cells than with controls (p < 0.05). LSN satellite cells were less responsive to the mitogenic effects of chicken serum (p < 0.05) and differentiation rates were lower compared with controls (p < 0.05). There was a greater (p < 0.05) number of insulin-like growth factor receptors on LSN satellite cells compared with controls. The IGF receptor binding affinities (Kds) between the two cell lines were similar (p > 0.05). The results suggest that a defect in satellite cell physiology may contribute to the skeletal muscle weakness seen in the LSN line.

Satellite cells were isolated from the skeletal muscles of turkey varieties which grow at different rates to explore cellular mechanisms that may influence the rate of muscular growth. Satellite cells from the fast growing variety (Nicholas) were more responsive to insulin-like growth factors (IGFs) and insulin, and less responsive to fibroblast growth factor than were cells derived from the slow growing (Merriam's) turkey. IGF receptor affinities were similar between the Nicholas and Merriam's turkey satellite cells. The results suggest that differences in the responses of satellite cells to growth factors may influence rates of skeletal muscle accretion and whole body growth.