Dietary manipulations influence the composition of RBC membranes and affect the thermal behaviour of their phospholipids

Two of three groups of cows were fed fat supplemented diets containing a relatively high proportion of C16:0, C18:0, C18:1 and a low proportion of C18:2 and C18:3 fatty acids (FAs). The 3rd group was the control one. By differential scanning calorimetry we examined the thermal behaviour of the phospholipid (P) mixture extracted from RBC membrane and we related the observed fluidity to the distribution of the different Ps and to their FA composition. Samples with approximatively the same P composition, with saturated (S) and unsaturated (U) FAs present at the same percentage, showed two well defined transition temperatures. The first was in the range 22.5-26.0 °C and the second one between 33.5 and 38.5 °C. If U>S one or, sometimes, two transitions were observed, both at lower temperatures than the above mentioned. When S>U one or two transitions were again observed; the first one was in the range 22.5-26.0 °C while the 2nd one, when observed, was at a lower value and then closer to the first transition. These results show a dependence of the fluidity from the lipid content of RBC membrane and suggest that dietary manipulations may have a not yet well considered functional significance.