Fatty acid synthesis in rat testes injected intratesticularly or incubated with 1-¹⁴C acetate

Abstract

Fatty acid synthesis was studied in testes of young and adult rats either injected intratesticularly or incubated with 1-¹⁴C acetate. The pattern of¹⁴C incorporation into lipids and individual fatty acids in the two age groups was similar but results obtained with intratesticular injection differed considerably from those obtained in the in vitro studies. In the former more than 70% of the¹⁴C incorporated in total lipids was in phosphatides, with about 15% in triglycerides and only minor amounts in cholesteryl esters and free fatty acids. Most of the¹⁴C incorporated into total fatty acids was in saturated acids (predominantly 16∶0). A small amount of¹⁴C was in the higher polyenes and there was a progressive increase with time after acetate injection in the¹⁴C content of 22∶5 W6. In testes incubated with 1-¹⁴C acetate, the phosphatide, triglyceride, and free fatty acid fractions had similar amounts of¹⁴C. In the total fatty acid fraction about 40% of the incorporated¹⁴C was in saturated acids (predominantly 14∶0 and 16∶0) and about 50% in the higher polyenes. Twenty carbon polyenes and 22∶5 W6 had significant¹⁴C incorporation, but most of the¹⁴C was in 22∶4 W6. About 80% of the¹⁴C in the latter compound was in the carboxyl carbon, indicating its origin from endogenous 20∶4 W6 elongated by the added 1-¹⁴C acetate used as substrate. The¹⁴C 22∶4 was present predominantly in the triglyceride and phosphatide fractions with minor amounts in other lipids.¹⁴C-labeled compounds of retention time greater than 22∶5 were also present in all lipid fractions.