Fasting increases tissue uptake and interconversion of plasma unesterified linoleic acid in guinea pigs.
A large part of the arachidonic acid (20:4 n-6) pools in some extrahepatic tissues can be formed by local interconversion of linoleic acid (18:2 n-6) taken up as free fatty acid (FFA) from blood in both rats and guinea pigs. This study investigates the rate of uptake and interconversion of unesterified 14C-18:2 by different tissues in fasted guinea pigs. The initial half-life of 14C-18:2 in plasma was 5.8 s. The average concentration of plasma FFA was 551.3 nmol ml-1 and of plasma FFA-18:2 was 67.3 nmol ml-1. The total amount of 20:4 formed in the liver was 1.8 +/- 0.3 nmol min-1, which was lower than that in the gastrointestinal tract (3.1 nmol min-1), bone marrow (6.0 nmol min-1) and lung (2.1 nmol min-1). Due to the fast turnover and higher concentration of plasma FFA-18:2 in the fasting state, the retained 18:2 in tissue lipids was 5.8-25.6-fold higher than that in fed guinea pigs [L. Zhou et al. Biochim. Biophys. Acta 1349 (1997) 197-210]. The total delta 6-desaturase products both in liver and in extrahepatic tissues were also increased, 3.8-fold in liver, 7.2-fold in upper small intestine, 6.0-fold in colon, and 6.5-fold in bone marrow. The increased rate of tissue uptake of FFA during fasting is thus linked to an increased local interconversion of plasma FFA-18:2, which is an important source of 20:4 in some extrahepatic tissue in guinea pigs.
Zhou
L
L
Cell Biology Department 1, University Hospital, Lund, Sweden.
Nilsson
A
A
D000818:Animals; D016718:Arachidonic Acid / Q000097:blood / Q000378:metabolism; D001693:Biological Transport, Active; D005215:Fasting / Q000378:metabolism*; D044943:Fatty Acid Desaturases / Q000378:metabolism; D005230:Fatty Acids, Nonesterified / Q000097:blood / Q000378:metabolism; D006168:Guinea Pigs; D007700:Kinetics; D019787:Linoleic Acid / Q000097:blood* / Q000378:metabolism*; D050602:Linoleoyl-CoA Desaturase; D008297:Male; D051381:Rats; D014018:Tissue Distribution