The effect of long‐chain monoenes on prostaglandin E₂ synthesis by rat skin

Abstract

In order to ascertain whether the dermal lesions observed in male rats fed rapeseed oils are due to impaired prostaglandin biosynthesis, endogenous levels of prostaglandin E2 (PGE2) in skin and the capacity of this tissue to synthesize PGE 2 from arachidonic acid was investigated. Male Sprague-Dawley rats were fed from weaning for 8 weeks either a standard rat diet (chow) or semlsynthetic diets containing 20% by weight of the following fat sources: corn oil; commercial lard; commercial lard to which was added 5.4% free erucic acid; rendered pig fat; or the following rapeseed oils: Brassica napu$ var. Zephyr; B. campestris var. Span; B. campestris var. Arlo (15%) and var. Echo (85%) designated HEAR (high erucic acid rapeseed). The long-chain monoene content (18:1, 20:1, and 22:1) of the diets fed ranged from 30 to 71 mole % and that of skin from 27 to 74 mole %. A significant (P < 0.01) correlation was found between the level of 18:2n-6 in the diet and the endogenous PGE 2 levels in skin and the capacity of this tissue to synthesize PGE 2. No relationship was found between these two PGE2 parameters and the level of erucic acid in the diet. The rate of turnover of PGE2 appeared to be lower in rats fed rapeseed oil as evidenced by the relatively high endogenous PGE 2 levels when these oils were fed (96 to 105/ag/g). On the other hand, the lowest capacity for PGE 2 synthesis was found with skin from rats fed Zephyr rapeseed oil, rats which also had the most severe incidence of hair loss and dermal lesions. Significant (P < 0.01) negative correlations were observed between the level of monoenes and specifically the level of oleic (18:1n-9) acid in the diets and PGE2 synthesis capacity of skin, possibly confirming the known inhibitory effect of 18:1n-9 on the prostaglandin synthesizing enzyme system. 1Contribution No. 687, Animal Research Institute.

The relationship of dietary fats to prostaglandin biosynthesis

“…This was attributed to the accumulation of erucic acid in the cholesterol fraction, which cannot serve as a precursor of PG. Hulon and Kramer (30) fed several varieties of rapeseed oil to rats and measured PGE 2 synthesis in skin. The rapeseed oils did not alter endogenous PGE 2 levels but did depress PGE?…”