Ky. Kwan et al., INHIBITORY EFFECT OF LINOLEIC-ACID ON CHAIN ELONGATION AND DESATURATION OF 18 2 C,T-ISOMERS IN LACTATING AND NEONATAL RATS/, Lipids, 33(4), 1998, pp. 409-416
The previous studies showed that dietary 18:2 c,t isomers could be cha
in-elongated and desaturated to produce unusual 20:4 isomers. The pres
ent study was undertaken to determine the minimal amount of 18:2n-6 re
quired to suppress the chain elongation and desaturation of 18:2 c,t i
somers in the lactating and neonatal rats when animals were fed 15% pa
rtially hydrogenated canola oil diet containing 1.72% energy as 18:2 c
,t isomers and varying amounts of free 18:2n-6. These diets induced ma
rginal essential fatty acid (EFA) deficiency states (0.56% energy 18:2
n-6) to EFA adequacy (2.56% energy 18:2n-6). After feeding for 50 d, t
he female animals were mated with males by overnight pairing. After co
nception, the lactating rats were killed, together with one pup from e
ach dam, at term and day 26 of lactation. Two unusual 20:4 isomers in
both maternal and neonatal liver phospholipids were identified as 20:4
Delta 5c,8c, 11c,14t and 20:4 Delta 5c,8c,11c,15t, which were derived
from 18:2 Delta 9c,12t and 18:2 Delta 9c,13t, respectively. The resul
ts showed that 18:2n-6 at about 2.0% of total energy in maternal diet
was required to block the production of 20:4 Delta 5c,8c,11c,14t and 2
0:4 Delta 5c,8c,11c,15t in the maternal liver, whereas 18:2n-6 at abou
t 2.5% of total energy in maternal diet was required to suppress produ
ction of these unusual 20:4 isomers in the neonatal liver.