Comments on the paper “The nephrotoxicity risk in rats subjected to heavy muscle activity” by Gülsen Oner and Selma Cirrik (2009) Journal of Sports Sci- ence and Medicine 8, 481-488” and response of the authors

Abstract

I have read with great interest the work reported by Gül- sen Oner and Selma Cirrik (2009) entitled “The nephro- toxicity risk in rats subjected to heavy muscle activity”. The authors reported that LDL-Cholesterol results of the serum from the rats were calculated by subtracting the HDL-Cholesterol from the Total Cholesterol. I am, however, of the opinion that the formula: LDL- Cholesterol = Total Cholesterol - HDL-Cholesterol should not have been applied by the authors, because the contribution of VLDL-Cholesterol to the Total Choles- terol has not been accounted for. Rats have a high HDL- Cholesterol level with relatively low VLDL-Cholesterol and very low levels of LDL-Cholesterol (Terpstra et al., 1982). The formula: Total Cholesterol = VLDL- Cholesterol + LDL-Cholesterol + HDL-Cholesterol, is generally accepted as a convenient approximation, be- cause the LDL fraction is heterogenous and contains intermediate-density lipoprotein (IDL), with a density of 1.006-1.019 kg/L, the main LDL, with a density of 1.019-1.063 kg/L and Lipoprotein (a) (Nuack et al., 2002; Rifai and Warnick, 2006). LDL-Cholesterol can be estimated using both di- rect and indirect methods. In the indirect methods a num- ber of lipid-related analytes are measured and the results of these analytes are then used in the calculation of the LDL-Cholesterol (Rifai and Warnick, 2006). The two indirect methods of LDL-Cholesterol estimation are beta- quantification and the Friedewald equation.