Application of an ultraviolet (UV) spectroscopic method for measuring lipoprotein cholesterol in diabetic hypothyroid...

Methods for the isolation and quantitation of cholesterol involve time-consuming chromatographic procedures coupled with the development and measurement of color complexes. The intensity of most color complexes varies with time. This study was undertaken to develop a UV spectrophotometric method to measure cholesterol concentration in plasma lipoprotein fractions. The developed method compared favorably with other methods (chemical and enzymatic) and was then used to investigate the effects of diabetes and hypothyroidism on the lipoprotein cholesterol in rats. Lipoprotein fractions from fasted rats were obtained by gradient ultracentrifugation. Aliquots of the very low-density lipoprotein (VLDL), low-density lipoprotein (LDL) and high-density lipoprotein (HDL) layers were extracted into chloroform-methanol-water. Following hydrolysis of lipid extracts, the solvent was evaporated and the residue was dissolved in ethanol and read in the UV recording spectrophotometer. At 203 nm, a linear relationship between optical density and concentration of cholesterol was obtained. The results obtained with the new method were compared with those obtained using chemical and enzymatic methods and the statistical difference among the methods was insignificant (p>0.05). From the results of our comparative studies of the methods, it was concluded that the UV method is valid for measuring cholesterol in lipoprotein fractions. The method has the advantage being rapid, nondestructive and cost-effective.