A comparison of magnesium deficiency, cold acclimation and thyroxine administration on mitochondrial fatty acid composition.

Abstract

A study was made to compare the effects of dietary magnesium deficiency, cold acclimation, and thyroxine administration on liver mitochondrial fatty acid composition. Groups of singly caged rats were fed synthetic diets containing either a control level (61 mg %) or a low level (4 mg %) of magnesium, and of these some were kept in the cold (5 ± 2°) and others at normal colony room temperature (23 ± 2°). A selected number of these rats were made hyper-thyroid by ip injection of 2 mg/100 g body weight of L-thyroxine sodium daily for 8 days before sacrifice. The fatty acid composition of the mitochondrial lipids was determined by gas chromatography. Cold acclimation alone significantly decreased the percentages of palmitic and arachidonic acids and increased the percentages of myristoleic, stearic, and linoleic acids. Throxine treatment increased the percentage of stearic acid and decreased linoleic and arachidonic acids. Magnesium deficiency, on the other hand, had little effect on the major components of the mitochondrial fatty acids and no effect on the total unsaturated fatty acids. It is concluded that mitochondrial swelling and uncoupling produced by magnesium deficiency does not seem to be related to changes in the total unsaturation of mitochondrial fatty acids.