Sterol metabolism. 4. The absorption of 7-dehydrocholesterol in the rat

Abstract

The distribution of total sterols, 7-dehydrocholesterol and lathosterol between the various cell fractions of intestinal mucosa of fasting rats and animals dosed with 7-dehydrocholesterol has been determined. In both groups of animals, about 50% of the total sterols in the tissues was associated with the microsomes and mitochondria, 30% with the supernatant or groundplasm and 10% with the "cell debris and nuclei" fraction. The mito-chondrial fraction of the dosed rats contained more of the total sterol (15%) than the corresponding fraction from fasting animals (10%). In agreement with previous work on the guinea pig, the various sterols were uniformly distributed among the components of the mucosal cells of both fasting and dosed groups, implying that the accumulated dietary sterol can exchange or mix with the endogenous sterols of the cell components. It is also postulated that in the rat the uptake and exchange of sterols between the mucosal cell lipoprotein plays an important role in the absorption of sterols. The sterols in excess of the fasting level which are finally transferred to the lymph will, however, contain a mixture of the dietary and endogenous types displaced by the exchange process. A large part of the 7-dehydrocholesterol absorbed from the intestine is also reduced within the mucosa to lathosterol.