The effect of polar head group substitution on phospholipid methylation and the beta-adrenergic response in C6 glial cells

Regulation of polyunsaturated fatty acid metabolism in tissue phospholipids of obese (fa/fa) and lean (Fa/-) Zucker rats. 1. Effect of dietary lipids on cardiac tissue

The present investigation addressed three questions: (i) Does the obese syndrome alter the fatty acid composition of cardiac tissue and membrane phospholipids in obese (fa/fa) rats? (ii) Are changes, if they occur, similar to those reported for tissues of the genetically obese (ob/ob) mouse? (iii) Can cardiac tissue phospholipids and their component fatty acids be modified by dietary lipids and if so does this occur to the same extent in both fa/fa and lean (Fa/-) rats? Proportions of polyunsaturated fatty acids (PUFA) in cardiac total phospholipids of fa/fa rats differed significantly from those of Fa/- rats and from those reported for ob/ob mice. Increased 18:2n-6 and decreased 20:4n-6 and 22:6n-3 in fa/fa rats indicated impaired PUFA metabolism, possibly reduced delta 6 and/or delta 5 desaturase activity, compared with Fa/- rats. No differences in hepatic delta 6 and delta 5 desaturase activity between fa/fa and Fa/- were found but enhanced activity of delta 9 desaturase activity in fa/fa as compared to Fa/- was evident. Inclusion of sunflower oil (SO) or triolein (TO) at 5% and 20% by weight in the diet elicited marked changes in the fatty acyl composition of cardiac phospholipids in both fa/fa and Fa/- rats when compared with animals fed the control Oxoid diet alone. Supplementation with triolein was most effective, reducing 18:2n-6 and increasing 20:4n-6 proportions in fa/fa rats so that they resembled those in Fa/- rats fed the control Oxoid diet. The type of fat rather than the amount of its dietary intake appears to be the main determinant of the observed changes in phospholipid composition.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased methylation of chloroform extractable products in brain membrane preparations after propranolol injection to the rat

1. One and four hours after acute or chronic (8 days) intraperitoneal injection of propranolol to rat at doses up to 25 mg/kg, a beta-adrenergic receptor blockage occurred in brain homogenates, as monitored by [3H]dihydroalprenolol binding. 2. A dose-dependent increased methylation of chloroform extractable products was observed (acute treatment: 18% increase, chronic treatment: 136% increase for the dose of 25 mg/kg). 3. The implication of beta-adrenergic receptors in this effect was studied and this revealed that: (a) acute intraperitoneal injection of the less active propranolol stereoisomer (+) did not produce any effect; (b) the chronic intraperitoneal injection of salbutamol, a beta-adrenergic receptor agonist, induced a decreased methylation of chloroform extractable products (62% decrease for the dose of 2.5 mg/kg). 4. It is concluded that injection of beta-adrenergic antagonist to the rat increases basal methyltransferase activity in the brain. This induces a decreased sensitivity of the enzyme activity to noradrenaline.