Calcium, collagen dose, gender and fasting affect the response of rat platelet thromboxane formation to extremes in dietary linoleate.
Platelet thromboxane synthesis in response to supplemental linoleate in the diet has been very inconsistent. The objective of this study was to investigate potential confounding factors known to affect platelet thromboxane synthesis. Citrated whole blood was recalcified with varying Ca2+ concentrations and challenged with low or high dose collagen preparations to induce extreme ranges of thromboxane synthesis from endogenous arachidonate pools by rat platelets. Male and female weanling rats were fed 0.0, 1.0 or 23 energy percent linoleate for 11 to 13 weeks. Fasting tended to enhance thromboxane synthesis. Both fasted and fed females showed slightly faster rates of thromboxane synthesis than males. Essential fatty acid deficiency depressed (P less than 0.01) thromboxane synthesis; the degree of this depression was inversely related to the level of recalcification (68% for 0.0 mM Ca2+, 36% for 2.5 mM Ca2+ and 20% for 5.0 mM Ca2+) when challenged with the high dose collagen. Essential fatty acid deficiency depressed platelet phospholipid arachidonate concentration 26%. Only blood from fed females stimulated with a mild challenge responded to excess dietary linoleate, and a 62% (not statistically significant) depression in TX synthesis was observed and this was associated with a decrease in platelet phospholipid arachidonate concentration.