Effect of hypo- and hyperthyroidism on the function and metabolism of macrophages in rats

The effect of thyroid hormones on monocyte migration, phagocytic capacity and hydrogen peroxide production by macrophages and the effect of these hormones on glutamine and glucose metabolism was investigated. The experiments were performed on resident, thioglycollate- and BCG-stimulated cells from hypo- and hyperthyroid rats. High plasma levels of thyroid hormones suppressed the migration of monocytes and hydrogen peroxide production, whereas hypothyroidism did not affect cell migration but raised the phagocytic capacity and the hydrogen peroxide production. Hyperthyroidism increased the activities of glutaminase and hexokinase and the rates of decarboxylation of [U-14C]-glutamine and [U-14C]-glucose in inflammatory and activated cells. Hypothyroidism stimulated glucose metabolism and had only a slight effect on glutaminolysis. The activity of the TCA cycle was, however, diminished in the presence of high plasma levels of thyroid hormones and enhanced by the hypothyroid state. These findings suggest that the functional changes are more likely to be related to the activity of the TCA cycle rather than to glutaminolysis and glycolysis.