Effect of salt-loading and spontaneous hypertension on in vitro metabolism of [1-14C]linoleic and [2-14C]dihomo-gamma-linolenic acids.

The present study compared the effect of spontaneous hypertension and salt-loading on in vitro metabolism of 18:2n-6 (linoleic acid) and 20:3n-6 (dihomo-gamma-linolenic acid). Ten weanling spontaneously hypertensive rats (SHR) and 10 normotensive Wistar-Kyoto rats (WKY) maintained on a rodent lab chow were given tap water with (n = 5) or without (n = 5) addition of 1% NaCl for 4 weeks. Thereafter, animals were killed and liver microsomes were prepared. Aliquots of microsomes suspended in the phosphate-sucrose buffer containing MgCl2, ATP, CoA, and NADPH were incubated with 0.3 microCi of [1-14C]-18:2n-6 or [2-14C]-20:3n-6 at 37 degrees C for 15 min. The activity of delta 6- and delta 5-desaturases, and the distribution of radioactivity in different lipid fractions and in phospholipid fatty acids were determined. Results showed that both spontaneous hypertension and salt-loading suppressed the desaturation of radiolabeled 18:2n-6 and of 20:3n-6. Incubation of microsomes with [1-14C]-18:2n-6 resulted in 29% of radioactivity being associated with phospholipid fraction, of which 3% was associated with 18:3n-6. Incubation with radiolabeled 20:3n-6 resulted in 30% of the radioactivity being incorporated into phospholipids, of which 50% was associated with 20:4n-6 (arachidonic acid). Salt-loading suppressed the incorporation of radiolabeled fatty acids into phospholipids, more so in SHR than in WKY. Thus, salt-loading not only suppressed the desaturation of 18:2n-6 and 20:3n-6, but also interfered with the acylation of n-6 fatty acids into the phospholipid fraction.