Transfer of exogenous cholesterol to microsomes of hepatocytes investigated with [3H]desmosterol tracer

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Abstract
The feasibility of using exogenous [3H]desmosterol as a mass metabolic tracer for exogenous nonesterified cholesterol in [rat] hepatocytes is investigated with albumin-bound nonesterified cholesterol containing [3H]desmosterol and [14C]cholesterol tracers. The amounts of uptake and metabolism of exogenous cholesterol monitored by either tracer are the same. The conversion of [3H] desmosterol into [3H]cholesterol by the .DELTA.24-sterol reductase in the microsomes can be used as an estimate for the mass transfer of exogenous cholesterol to the microsomes. Only a small fraction of exogenous cholesterol that was transferred to the microsomes was metabolized into bile acids and steryl esters. The technique of estimating the mass transfer of exogenous cholesterol to the microsomes with [3H]desmosterol may be of importance in investigations dealing with the effect of exogenous plasma cholesterol on changes in the physiological functions of the endoplasmic reticulum in the cells.