A comparative study of the metabolism of n-9, n-6 and n-3 fatty acids in testicular cells from immature rat

• Published in: Biochimica et biophysica acta 1998-05, Vol.1392 (1), p.59-72
• Main Authors: Retterstøl, Kjetil, Haugen, Trine B., Woldseth, Berit, Christophersen, Bjørn O.
• Format: Article
• Language: English
• Subjects: Age Factors; Animals; Cell Separation; Dietary Fats, Unsaturated - metabolism; Docosahexaenoic acid; Docosapentaenoic acid; Essential fatty acids; Fatty Acids, Omega-3 - metabolism; Fatty Acids, Omega-6; Fatty Acids, Unsaturated - metabolism; Male; Rats; Rats, Sprague-Dawley; Sertoli cells; Sertoli Cells - metabolism; Testicular cells; Testis - cytology; Testis - metabolism; Tetracosaenoic acid; Weaning
• ISSN: 0005-2760; 0006-3002; 1879-145X
• DOI: 10.1016/S0005-2760(98)00021-6

Dietary 18 and 20-carbon fatty acids of the n-6 and the n-3 families are metabolized to 22:5, n-6 and 22:6, n-3 by a sequence of specific desaturases and chain elongation via 24-carbon intermediates. This pathway is regulated so that more 22:6, n-3 than 22:5, n-6 is found in the tissues. Rat testis is an exception since 22:5, n-6 is present in large proportions in this organ. Therefore rat testis appears to be interesting for studies of the detailed synthesis of 22:5, n-6 compared with that of 22:6, n-3. By using fresh preparations of rat testicular cells from 19-day-old rats enriched in Sertoli cells, we compared the metabolism of 1- 14C-labelled n-3, n-6 and n-9 fatty acids. The testicular cells actively synthesized 22:6, n-3 and 22:5, n-6, but not 22:4, n-9 from the 18 and 20-carbon precursors. Of 200 mol 14C-labelled C 18 and C 20 fatty acids added initially, approximately 20-40 mol were found as 24-carbon intermediates after 24 h of incubation. This indicates that the balanced capacity of elongation, desaturation and chain shortening favours the accumulation of 24-carbon intermediates in these cells. One exception was [1- 14C]20:3, n-9 which was efficiently elongated to 22:3, n-9 but not to C 24 fatty acids. Our data suggests that the poor elongation of n-9 fatty acids from C 22 − to C 24 may be an important hindrance in the synthesis of 22:4, n-9. The efficient synthesis of 22:5, n-6 may also partly explain why this is the major 22-carbon fatty acid in rat testis.