Abstract
Determinations were made for subcellular distribution of fatty acids of lipids in the membrane and the cytoplasm of myofibers and intramuscular adipocytes in tissues from twelve USDA Select beef carcasses, from animals ranging in age from 12 to 20 months. The carcasses were fabricated to obtain these individual muscles: longissimus dorsi (LD), psoas major (PM) and semitendinosus (ST), and adipose tissue--the subcutaneous (SQ) adipose tissue overlying the LD and ST muscles and intramuscular (IM) adipose tissue from the heavily marbled area of the LD near the 13th rib. Cholesterol quantifications for the subcellular fractions of IM were made as were the identification of fatty acids. The raw tissues were homogenized and cellular components were separated by ultracentrifugation into the membrane plus microsomal fraction and the cytosolic or cytoplasmic fraction for lipid and cholesterol extractions. After methylation with 14% boron trifluoride in methanol, lipids were derived and resulting fatty acid methyl esters were analyzed by use of a column packed with DEGS + 1% H3PO4 from 480 individual gas chromatography runs. Lipid extracts of IM adipose tissue were saponified, evaporated under nitrogen and the residue used for the colorimetric determination of cholesterol. In every tissue except the IM, the fatty acids present in subcellular fractions in the largest amounts were C[18:1] (oleic acid), ranging from 32% to 42%, and C[16:0] (palmitic acid), ranging from 21% to 30%. The greatest percentages of oleic acid were found in the membrane over the cytoplasmic fractions except in the IM, the reversal was seen. Stearic acid (C[18:0]), ranging from 9% to 15% per fraction, was the third most abundant fatty acid across all tissues with the largest amount found in the membrane fraction. The saturated fatty acids in all tissues were more abundant in the cytoplasmic than in the membrane fraction, ranging from 41% to 45%. Monounsaturated fatty acids for all tissues were highest (38% to 49%) in the cytoplasmic fraction, with the exception of the IM in which 46% was in the membrane and 43% was in the cytoplasm. Polyunsaturated fatty acids were present in the range of 5% to 20%, with muscle and adipose tissues containing more of these fatty acids in the membrane fraction...
Sweeten, Mary Claire Kinney (1988). Subcellular distribution and composition of lipids in myofibers and intramuscular adipocytes. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -781554.