ABSTRACT
The relation between lipolysis and the metabolic fibre type was investigated during refrigerated storage of rabbit muscles. Free fatty acid, monoacylglycerol and diacylglycerol contents and free fatty acid composition were compared in five muscles immediately after slaughter and after a 7-day-storage at 4°C. The results showed that. (1) The amount of free fatty acids sharply increased during the refrigerated storage (from 2-10 to 11-32 mg/100 g of muscle), especially that of long chain polyunsaturated fatty acids (from less than 0.1 to 1.4-3.3 mg/100 g of muscle). (2) The glycolytic muscles contained 1.5 times less free fatty acids than the oxidative ones. However, the rates of phospholipid and triacylglycerol hydrolysis were not related to the metabolic type of the fibres. (3) The contribution of phospholipids to free fatty acid fraction was twice that of triacylglycerols in the glycolytic muscles whereas it was similar or lower to that of triacylglycerols in the oxidative muscles.
ABSTRACT
The fatty acid composition of individual phospholipid classes as related to metabolic type of fibre in the rabbit was studied. The fatty acid composition of the individual phospholipid classes of five muscles were compared: two glycolytic ones (Longissimus lumborum and Psoas major), two oxidative ones (Soleus and Semimembranosus propriosus,) and an intermediate one (Gastrocnemius laterale). It was shown that except for phosphatidyl inositol (PI), the fatty acid compositions of the main phospholipid classes were strongly related to the metabolic type of the fibres; phosphatidyl ethanolamine (PE) of oxidative muscles contains less 18:2 n-6 and more 18:0 and long chain PUFA of the n-6 and n-3 series than that of glycolytic ones; phosphatidyl choline (PC) of oxidative muscles contains more 18:0 and less 16:0 and 18:2 n-6 than that of glycolytic ones; cardiolipin of the oxidative muscles contains less 18:2 n-6 than those of the glycolytic ones. These differences in fatty acid composition of PE, PC and cardiolipin explain a large part of the differences in fatty acid compositions of the total phospholipids of glycolytic and oxidative muscles.
ABSTRACT
During perinatal development, docosahexaenoic acid (22:6n-3) accumulates extensively in membrane phospholipids of the nervous system. To evaluate the n-3 fatty acid requirements of fetal and suckling rats, we investigated the accumulation of 22:6n-3 in the brain and liver of pup rats from birth to day 14 postpartum when their dams received increasing amounts of dietary 18:3n-3 (from 5 to 800 mg/100 g diet) during the pregnancy-lactation period. The fatty acid composition of brain and liver phospholipids of pups, as well as that of dam's milk, was determined. At birth, 22:6n-3 increased regularly to reach the highest level when the maternal diet contained 800 mg 18:3n-3/100 g. On days 7 and 14 postpartum, brain 22:6n-3 plateaued at a maternal dietary supply of 200 mg/100 g. Docosapentaenoic acid (22:5n-6) had the opposite temporal pattern. The unusually high concentration of eicosapentaenoic acid (20:5n-3) in liver and dam's milk observed at the highest 18:3n-3 intake suggests an excessive dietary supply of this fatty acid. All these data suggest that the n-3 fatty acid requirements of the pregnant rat are around 400 mg 18:3n-3 and those of the lactating rat at 200 mg (i.e., 0.9 and 0.45% of dietary energy, respectively). The values of 18:3n-3 and 22:6n-3 milk content which allowed brain 22:6n-3 to reach a plateau value in suckling pups were 1% of total fatty acids and 0.9% (colostrum) to 0.2% (mature milk), respectively. These levels are similar to those recommended for infant formulas.
Subject(s)
Brain/metabolism , Fatty Acids, Omega-3/administration & dosage , Fatty Acids, Omega-3/metabolism , Lipid Metabolism , Liver/metabolism , Animal Nutritional Physiological Phenomena , Animals , Animals, Newborn , Animals, Suckling , Brain Chemistry , Docosahexaenoic Acids/metabolism , Fatty Acids/analysis , Fatty Acids, Omega-3/pharmacology , Female , Lactation , Lipids/chemistry , Liver/chemistry , Milk/chemistry , Nutritional Requirements , Phospholipids/analysis , Phospholipids/metabolism , Pregnancy , Rats , Rats, Wistar , alpha-Linolenic Acid/metabolismABSTRACT
The purpose of this study was to specify the intramuscular lipid characteristics which are related to the metabolic type of muscles. Two glycolytic muscles (Longissimus lumborum and Psoas major), two oxidative ones (Soleus and Semimembranosus propriosus) and an intermediate one (Gastrocnemius laterale) were dissected from rabbit carcasses. The results showed that:
