LIPID COMPOSITION OF THE PECTORAL MUSCLES OF CHICKENS WITH INHERITED MUSCULAR DYSTROPHY.

Abstract

Asmundson and Julian (1,2) reported the presence of a recessive autosomal gene (am) in New Hampshire chickens which produces in the homozygous bird a condition quite similar to certain forms of muscular dystrophy in man(3). The superficial pectoral muscles of such adult birds contained considerably more fat than those of normal birds (4,5). Elevated fat content has also been found in certain muscles of mice with muscular dystrophy by Shull and Alfm-Slater(6) and in some types of muscular dystrophy in man (3). This investigation was undertaken to determine the nature of the fat deposited intramuscularly in chickens with inherited muscular dystrophy. An increase in the triglyceride fraction and a decrease in the phospholipid fraction relative to other lipids constitute the major differences in the dystrophic muscle when compared with the normal muscle. Methods. Seven pairs of 36-week-old normal and muscular dystrophic female New Hampshire birds were used in the study. The animals were sacrificed and the left superficial pectoral muscles were excised, quick-frozen in a dry ice-acetone bath and stored at —20°C. They were thawed and used as needed. A 0.5-0.8 sample g of wet muscle was placed in a vacuum oven at 70° for 12 hours to determine the moisture content by weight difference. Protein was determined by the Kjeldahl method (N × 6.25) and hydroxyproline was determined by the technique of Neuman and Logan(7). The hydroxyproline content was used as a measure of collagen or connective tissue. The fat was extracted from the muscle by the CHCl3:CH3OH:H2O method of Bligh and Dyer(8). The CHCl3 layer containing the lipid, was evaporated in a 60° C water bath under a stream of N2. Approximately 70 mg of this fat was chromatographed on a 3.0 g silicic acid-Hiflo Supercell column (70: 30 w/w), and eluted by the scheme of Barron and Hanahan(9).