Effects of a medium-chain triglyceride:fish oil emulsion administered intravenously to omega3 fatty acid-depleted rats on cationic fluxes in aortic rings

The handling of 45Ca and 86Rb by aortic rings obtained from rats depleted in long-chain polyunsaturated omega3 fatty acids (second generation) was examined in vitro over 10 to 60 min incubation at either increasing concentrations of extracellular K+ (5, 3 and 60 mM) in the case of 45Ca net uptake or in the absence and presence of ouabain (50 microM) in the case of 86Rb uptake. The omega3-depleted rats were injected intravenously 120 min before sacrifice with 1.0 ml of either an omega3 fatty acid-rich medium-chain triglyceride:fish oil emulsion (MCT:FO) or a control medium-chain triglyceride:olive oil emulsion (MCT:OO). In the MCT:OO-injected rats, the rise in extracellular K+ concentration failed to stimulate 45Ca net uptake, whilst the prior injection of the MCT:FO emulsion restored the expected increase in 45Ca net uptake by aortic rings exposed to 60 mM K+. The absolute value for 86Rb net uptake after 10 or 60 min incubation and whether in the absence or presence of ouabain, which significantly decreased the uptake of 86Rb+ after 60 min incubation, only represented in the MCT:FO-injected rats 63.1+/-3.8% of the mean corresponding values found in MCT:OO-injected animals. These findings are consistent with the view that activity of cationic channels, such as the voltage-sensitive Ca2+ channel, the outflow of Ca2+ as mediated by either Na+-Ca2+ countertransport or a Ca2+-ATPase, the activity of Na+,K+-ATPase and the modality of K+ inflow by an oubain-resistant modality are all affected in aortic cells by the content of long-chain polyunsaturated omega3 fatty acids in membrane phospholipids.     

Preclinical investigations of a medium-chain triglyceride:fish oil emulsion. I. Effects of bovine milk lipoprotein lipase on lipid composition

The bolus intravenous injection of a novel medium-chain triglyceride:fish oil emulsion (MCT:FO, 8:2, w:w) was recently found to increase within 60 min the leucocyte and platelet phospholipid content of long-chain polyunsaturated omega3 fatty acids. The present report deals with the effects of bovine milk lipoprotein lipase on the lipid composition of this emulsion. The results are compared to those obtained with either a pure fish oil emulsion or a medium-chain triglyceride: long-chain triglyceride:fish oil emulsion (MLF, 5:4:1). Emphasis is placed on i) differences in the fate of distinct fatty acids initially present in the triglycerides, di glycerides and phospholipids, ii) the generation of unesterified fatty acids relative to their initial content in each emulsion, and iii) the time course for these various events. The comparison between the three emulsions under consideration also provides information relevant to their respective sensitivity to lipoprotein lipase and suitability in terms of the generation of distinct unesterified fatty acids, including long-chain polyunsaturated omega3 fatty acids. Furthermore, attention is drawn to the greater efficiency for the hydrolysis of fatty acids from diglycerides as compared to triglycerides and a transient increase in the paired C8:0/C10:0 ratio in the diglycerides generated from the MCT:FO or MLF emulsion. The present study thus affords novel information relevant to the possible use of the MCT:FO emulsion in human subjects.