Palmitic acid uptake by the rat soleus muscle in vitro

The rate of fatty acid uptake, oxidation, and deposition in skeletal muscle s in relation to total and unbound to albumin fatty acids concentration in the medium were investigated in the incubated rat soleus muscle. An immunoh istochemical technique was applied to demonstrate whether the albumin-bound fatty acid complex from the medium penetrates well within all areas of the muscle strips. It was found that the percentage of incorporation of palmit ic acid into intramuscular lipids was fairly constant, independently of the fatty acid concentration in the medium, and amounted to 63-72% for triacyl glycerols, 7-12% for diacylglycerols-monoacylglycerols, and 19-26% for phos pholipids. Both palmitic acid incorporation into the muscle triacylglycerol stores and its oxidation to CO2 closely correlated with an increase in bot h total and unbound to albumin fatty acid concentrations in the incubation medium. Under conditions of increased total but constant unbound to albumin palmitic acid concentrations, the incorporation of palmitic acid into tria cylglycerols and its oxidation to CO2 were also increased, but to a lower e xtent. This supports the hypothesis that the cellular fatty acid metabolism depends not only on the availability of fatty acids unbound to albumin, bu t also on the availability of fatty acids complexed to albumin.