EVALUATION OF THE USE OF SERUM LATHOSTEROL CONCENTRATION TO ASSESS WHOLE-BODY CHOLESTEROL-SYNTHESIS IN RABBITS

Serum lathosterol concentration in rabbits was assessed as a possible indicator of whole-body cholesterol synthesis. In random-bred New Zealand White (NZW) rabbits fed a control diet or a diet containing either cholesterol, simvastatin, or cholestyramine, neither serum lathosterol concentration nor the serum lathosterol:total cholesterol ratio systematically corresponded with the anticipated rate of cholesterol synthesis. In control rabbits and those fed simvastatin or cholestyramine, whole-body cholesterol synthesis, which was calculated from the sterol balance, was correlated with serum lathosterol concentration when expressed relative to cholesterol in very low, intermediate, and low density lipoproteins (VLDL + IDL + LDL) (r = 0.61; n = 23; P = 0.002). The low correlation coefficient indicates that the predictive value of the lathosterol:(VLDL + IDL + LDL) cholesterol ratio is limited when applied to individual rabbits. Cholesterol and simvastatin feeding reduced the group mean serum lathosterol:(VLDL + IDI + LDL) cholesterol ratio, whereas cholestyramine in the diet raised the group mean ratio in the NZW rabbits. We conclude that the serum lathosterol:(VLDL + IDL + LDL) cholesterol ratio may be an indicator of group mean rates of whole-body cholesterol synthesis in rabbits but may not yield reliable information on individual rabbits. The lathosterol:(VLDL + IDL + LDL) cholesterol ratio predicted that in hyperresponsive inbred rabbits, showing an excessive hypercholesterolemia after cholesterol feeding, baseline whole-body cholesterol synthesis is lower than in hyporesponsive rabbits. Addition of cholesterol to the diet caused a reduction of predicted cholesterol synthesis in hypo- but not in hyper-responsive rabbits.