The lipid composition of the prepubertal and adult rat testis

Abstract

A quantitative study of the lipid components of maturing rat testes which includes data on the fatty acid components of individual phosphatides, triglycerides and cholesteryl esters has been made. Testicular lipids of prepubertal and adult rats have been isolated and separated into individual neutral lipid and phosphatide classes by silicic acid column chromatography. The lipid representing 2.2% of the tissue wet weight was about 80% phosphatide and 20% neutral lipid. Phospholipid distribution was as follows: phosphatidyl choline, 47.5%; phosphatidyl ethanolamine, 26.2%; phosphatidyl serine, 7.2%; phosphatidyl inositol, 2.3%; and sphingomyelin, 6%. Plasmalogens were found primarily in the phosphatidyl ethanolamine fraction. Free cholesterol, about 95% of total cholesterol, and triglyceride were the predominant classes found in the neutral lipid fraction; monoglyceride, trace amounts of diglyceride and other components were also detected. No conspicuous differences in the relative distributions of the lipid classes were observed between the immature and adult animal. The fatty acid composition of each of the isolated lipid classes was determined by gas-liquid chromatography. Comparable fractions of the neutral lipids and of phospholipid classes of both young and mature testes had similar fatty acid contents. Major fatty acids of the triglyceride fraction were palmitic, oleic, and docosapentaenoic; unsaturation increased in the older animal. About half of the fatty acids of the phosphatides were unsaturated; palmitic, stearic, oleic, arachidonic and docosapentaenoic acids represented most of the fatty acids found, but their relative distributions varied in individual phosphatides. β-Position fatty acids of phosphatidyl choline were predominantly oleic and arachidonic in the prepubertal animal but the concentration of docosapentaenoic in the adult increased to equal that of arachidonic. A similar relative distribution of unsaturated fatty acids was found in the phosphatidyl ethanolamine fractions, but large amounts of palmitic and stearic were also present. A marked increase in the concentration of docosapentaenoic acid was found in the triglyceride fraction as well as in individual phosphatide classes of the adult testes.