LIVER MICROSOMAL MEMBRANE FLUIDITY AND MICROSOMAL DESATURASE ACTIVITIES IN ADULT SPONTANEOUSLY HYPERTENSIVE RATS

Objective The purpose of the present study was to investigate liver mi crosomal membrane fluidity simultaneously with membrane fatty acid com position and desaturase activities in spontaneously hypertensive rats (SHR). Design and methods The membrane fluidity was determined, after electron spin resonance (ESR) measurement, in SHR compared with normot ensive Wistar-Kyoto (WKY) rats, by calculating the order parameter S f rom ESR spectra of 5-nitroxide stearate and 10-nitroxide stearate, use d as spin-labelled fatty acids, Desaturase activities were measured by incubating SHR and WKY rat liver microsomes with [C-14]-radiolabeled fatty acids as substrates for desaturation reactions, The fatty acid c omposition of liver microsomal membranes was determined by gas-liquid chromatography. Results Whereas no significant difference between S of 5-nitroxide stearate was observed for SHR and WKY rats, S of 10-nitro xide stearate was significantly lower in SHR than it was in WKY rat mi crosomal membrane, indicating that the core microsomal membrane fluidi ty was higher in SHR. Significant differences between fatty acid compo sitions were observed for SHR and WKY rat microsomal membranes, Delta 9 and n-6 Delta 6 microsomal desaturase activities were significantly lower in SHR. Conclusion These results suggest that the higher liver c ore microsomal membrane fluidity observed in SHR might be dependent on the increased proportion of mono-unsaturated fatty acids, Such observ ed modifications and the alterations in Delta 9 and n-6 Delta 6 desatu rase activities suggest that an impaired polyunsaturated fatty acid bi osynthesis is related to changes in microsomal membrane fluidity in hy pertension.