ABSORPTION AND TRANSPORT 367 



rats was 10% of that of cholesterol when the same amounts of the two 

 sterols were fed. Ingested tritium-labeled (^-sitosterol was found in the 

 blood, both as the free sterol and in the esterified form. This led to the 

 conclusion that enzymes capable of esterifying j8-sitosterol were present in 

 the animal body. 



(^-Sitosterol does not appear to have a predilection for any particular 

 tissue.^^ However, an especially high value in the bile sterol, observed in 

 one case of carcinoma, ma}^ indicate that the liver selectively excretes /?- 

 sitosterol in bile, and that bile contains a higher porportion of ingested 

 sitosterol than does liver or blood. 



Cook" has re^^ewed the present conclusions as to the absorption of 

 sterols. Of the C27 sterols, cholesterol is absorbed, in the presence of fat, 

 by man, by various mammals, and by birds. Lathosterol, cholestanol, 

 and 7-dehydrocholesterol, which accompany cholesterol, are absorbed by 

 rabbits, whereas coprostanol is not. The Cos sterols are poorly absorbed." 

 Ergosterol, from yeast and from certain fungi, is absorbed to some extent 

 by rats and hens, chalinasterol (ostreasterol), from oysters, is absorbed 

 by mice;*^ brassicasterol, from horse mussel {Modiolus, spp.) is absorbed 

 to a slight degree by rabbits. The C29 sterols are also poorly absorbed." 

 i8-Sitosterol, from the fats of higher plants, especially cereals, is only slightly 

 absorbed by man and by the rat, and stigmasterol, from soya bean, is not 

 absorbed at all by rats or by mice. Considerable data are available to in- 

 dicate that, in addition to the phytosterols, most cholesterol derivatives 

 are poorly absorbed. This is also the case with /3-cholestanol (dihydro- 

 cholesterol),^^'^^ and also with coprostanol.^^ Coprostenol, which is iso- 

 meric with cholesterol, is also not absorbed by mice or by dogs.^^-^^ More- 

 o\'er, it does not appear in the eggs of hens after being fed to this species, 

 which also suggests its non-absorbability.^^ Finally, Schonheimer and co- 

 workers*^ •^^•^'' observed that cholestanol and its isomers are not absorbed 

 from the gastrointestinal tract; of the C27-sterols, only cholesterol has the 

 distinction of being readily absorbed. 



There is some disagreement as to whether or not the C28-sterol, ergos- 

 terol (pro\'itamin D2) can be utilized. Thus, Schonheimer et al}^ failed 

 to demonstrate any deposition of ergosterol in mice, rats, rabbits, or dogs 

 after prolonged feeding of the sterol. On the other hand. Page and Men- 

 schick^- did note some absorption of ergosterol, as did also Hanahan and 



S8 M. Burger and W. Winterseel, Z. physiol. Chem., 202, 237-245 (1931). 

 " E. A. Evans, Jr., /. Biol. Chem., 115, 449-451 (1936). 

 «« R. Schonheimer and H. v. Behring, Z. physiol. Chem., 192, 102-111 (1930). 

 " R. Schonheimer, H. v. Behring, and V. Gottberg, Z. physiol. Chem., 208, 77-85 

 ri932). 



62 1. H. Page and W. Menschick, Biochem. Z., 221, 6-10 (1930). 



