A comparative study of the metabolism of n-9, n-6 and n-3 fatty acids in testicular cells from immature rat.
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 C18 and C20 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 C24 fatty acids. Our data suggests that the poor elongation of n-9 fatty acids from C22- to C24 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.
Retterstøl
K
K
Institute of Clinical Biochemistry, National Hospital, University of Oslo, N-0027 Oslo, Norway.
Haugen
T B
TB
Woldseth
B
B
Christophersen
B O
BO
D000367:Age Factors; D000818:Animals; D002469:Cell Separation; D004042:Dietary Fats, Unsaturated / Q000378:metabolism*; D015525:Fatty Acids, Omega-3 / Q000378:metabolism*; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated / Q000378:metabolism*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D012708:Sertoli Cells / Q000378:metabolism*; D013737:Testis / Q000166:cytology / Q000378:metabolism; D014886:Weaning
D004042:Dietary Fats, Unsaturated; D015525:Fatty Acids, Omega-3; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated