A MODEL FOR ESSENTIAL HYPERTENSION: METABOLIC STUDIES

The purpose of the study was to determine the extent to which blood pressures and tissue lipid levels are manipulated by dietary control of low levels of essential fatty acids in rat strains used as models of hypertensive and normotensive man. Analytical procedures included gravimetric total lipids, colorimetric cholesterol and phospholipids, fluorimetric triglycerides, and gas-liquid chromatographic fatty acids. Samples taken for analyses were plasma, liver, and kidney. The lipid extraction method employed a mixture of chloroform and methanol. The fraction separation method was solvent elution from silicic acid columns. The procedure for measuring blood pressures employed a physiograph and inflatable tail cuff. Diets for weanling spontaneously hypertensive rats (SHR) and Wistar/Kyoto rats (WKY) consisted of purified components, including corn oil at levels of 0, 1, and 5% by weight. The feeding period lasted 14 weeks. Total lipids tended to be lower in plasma, liver, and kidney of the SHR than the WKY. Liver triglyceride and kidney cholesterol and phospholipid (PL) were lower with liver PL higher in SHR than in WKY. Total individual fatty acids in plasma and in neutral lipid and PL fractions of liver and kidney exhibited several strain and diet differences. Among these were generally lower levels of essential fatty acids in the liver fractions and higher levels in the kidney fractions and in plasma of SHR and in WKY. These findings are consistent with a high metabolic rate in the SHR and suggest defective transport of essential fatty acids from the liver. Monounsaturated fatty acids were generally lower in SHR than in WKY fractions, suggesting either low desaturating enzymatic activity or a high level of desaturation with subsequent elongation of the monounsaturated fatty acids in the SHR.