EFFECT OF PROPYLTHIOURACIL-INDUCED HYPOTHYROIDISM ON MEMBRANES OF ADULT-RAT BRAIN

The effect of hypothyroidism on the lipid composition of myelin and sy naptosomes isolated from adult rat brain was investigated. The animals were made hypothyroid by adding 0.05% propyl-2-thiouracil to their dr inking water for four weeks. This pathological state resulted in a sig nificant increase in the relative percentage of choline glycerophospho lipids in synaptosomes with a concomitant decrease in ethanolamine gly cerophospholipids as compared to controls. In myelin, hypothyroidism s ignificantly influenced only the relative percentage of sulfatides. Th e effect of the hypothyroid state on mature brain was also reflected i n changes in the membrane fatty acid composition. Myelin and synaptoso mes showed an increase in arachidonic (20:4) and eicosatrienoic (20:3) acids and an increase in the fatty acid unsaturation index. Furthermo re, the 20:4/20:3 and 20:3/18:2 ratios were lower and higher respectiv ely, in treated animals. The data indicate that hypothyroidism affects the lipid composition of synaptosomes and myelin even though the effe cts were less pronounced in myelin. The lipid changes observed in hypo thyroidism may be of physiological significance, as it is well known t hat lipid composition modulates various membrane bound enzymes, transp orters and receptors.