The Effects of Streptozotocin Diabetes and of Dietary Protein Content on the Composition and Metabolism of Testicular Lipids

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Abstract
The effect of streptozotocin-induced diabetes on the fatty acid composition and metabolism in tests of rats on diets varying in protein content was investigated. The protein content of the diet (40, 20, 5%) had little or no effect on essential fatty acid metabolism during the 2 wk following injection of streptozotocin, but the 5% diet resulted in a high rate of mortality for diabetic rats. Increased amounts of octadeca-9,12-dienoic (linoleic or 18:2) acid and of eicosa-8,11,14-trienoic (dihomo-.gamma.-linolenic or 20:3) acid and decreased amounts of eicosa-5,8,11,14-tetraenoic (arachidonic or 20:4) acid were observed in testes of some but not all diabetic compared to pair-fed control rats 2 wk after injection of streptozotocin. Incorporation of 14C from [14C]18:2 into testicular lipids of these rats was determined 26 h after intratesticular injection. In some rats there was a greater amount of 14C in eicosa-11,14-dienoic acid (dihomolinoleic acid or 20:2) and 20:3 and less 14C in 20:4 of tests of diabetic than in those of control rats. The suggested impairment in conversion of 18:2 to 20:4 was studied further by using [14C]20:3 as the substrate for intratesticular injection. After administration of the [14C]polyene at 4 h, there was more 14C in 20:3 and less 14C in 20:4 and in docosa-7,10,13,16-tetraenoic (adrenic or 22:4) acid in testes of diabetic than in those of control rats. In diabetic rats at least 1 enzyme responsible for the decreased conversion of 18:2 to 20:4 is the .DELTA.5-desaturase.