PSYCHOSOCIAL STRESS, CATECHOLAMINES, AND ESSENTIAL FATTY-ACID METABOLISM IN RATS

To examine the effects of psychosocial stress and the ''stress hormone ,'' epinephrine, on essential fatty acid metabolism in rats, two studi es were conducted. In the first, the effects of four weeks of (i) soci al isolation and (ii) group housing (control) on liver microsomal Delt a(6) and Delta(5) n-6 desaturase activity were studied in group-reared male normotensive (Wistar Kyoto) and spontaneously hypertensive (SHR) rats (n = 5/group). The second study examined the effects of acute ip epinephrine (0.0, 1.0, 2.0, and 4.0 mg/kg) 6 hr prior to and followin g an ig dose (4 g/kg) of safflower oil (rich in 18:2n-6, LA) on plasma and liver LA, 20:4n-6 (AA), and LA/AA ratios in adult essential fatty acid deficient Sprague-Dawley rats (n = 6/group). In the first experi ment, isolation stress significantly inhibited the activity of Delta(6 ) (P < 0.05) and Delta(5) (P < 0.01) desaturase in the normotensive ra ts and of Delta(5) desaturase in the SHR (P < 0.05). In the second stu dy, epinephrine increased plasma and liver LA at doses 1.0 and 2.0 mg/ kg in most of the fractions examined, and suppressed AA levels. The re sponse of the LA/AA ratio to epinephrine varied between tissues and am ong lipid fractions, but increased this ratio at the moderate doses (2 .0-4.0 mg/kg) of epinephrine in most cases. These data suggest that ps ychosocial stressors are capable of inhibiting the rate limiting steps of essential fatty acid metabolism and that this response is more pro nounced in the SHR than in the Wistar Kyoto. They also suggest that ep inephrine is capable of altering the in vivo metabolism of essential f atty acids in the rat.