410 VIII. CHOLESTEROL AND RELATED STEROLS 



sented which indicates that cholesterol may not be an important inter- 

 mediate. 



(7) Conversion to Estrogens 



West and Todd^^ and others^^^'^^^~^^° have suggested that cholesterol 

 may be the mother substance of some of the estrogenic hormones, in ad- 

 dition to being the source of pregnanediol.^-^ 



{8) Conversion to 7-Dehydrocholesterol 



7-Dehydrocholesterol is generally recognized as provitamin D3. It has 

 been an open question whether or not the animal can synthesize 7-dehydro- 

 cholesterol from cholesterol. In a study of the distribution and source of 

 this dehydro compound, Glover, Glover, and Morton''- found that this un- 

 saturated substance was concentrated in the mucosae and lamina propria 

 of the duodenum of the guinea pig. The proportion of 7-dehydrocholes- 

 terol tends to increase as the animals increase in size, and when they ex- 

 hibit liver tubercles due to Pasteurella pseudotuberculosis, which is patho- 

 genic for rodents. It was demonstrated that cholesterol, when adminis- 

 tered orally, dissolved in ethyl myristate or ethyl olcate, is dehydrogenated 

 in the wall of the intestine by means of a dehydrogenase. It was con- 

 cluded that the animal is not dependent upon provitamin D as such, but 

 that it has the power to dehydrogenate cholesterol synthesized in its own 

 body.''^ Presumably 7-dehydrocholesterol can be converted into vitamin 

 D3 when that present in the skin is subjected to ultraviolet irradiation. 

 Bills^'*^ demonstrated that irradiation of the sterol molecule may cause a 

 break in the cyclopentenophenanthrene ring between carbons 9 and 10, 

 resulting in the formation of products which possess vitamin D activity. 



(9) Conversion to 7-Keto and 7-Hydroxy Compounds 



Although cholesterol, when injected as an emulsion intravenously into 

 rabbits, is rapidly removed from the circulation, it is not as rapidly metab- 

 olized as is 7-ketocholesterol or 7-hydroxycholesterol. Thus, although 

 Kendall and co-workers^"*- found that 6% of radioactive cholesterol was 



338 -^^ jj_ Pearlman, The Chemistry and Metabolism of the Estrogens, in G. Pincus and 

 K. V. Thimann, The Hormones, Vol. I, Academic Press, New York, 1948, Chapter X, 

 351-405 (pp. 360, 398). 



339 P. Rondoni, V. Carminati, and A. Corbellini, Z. physiol. Chem., 2U, 71-80 (1936). 

 3« I. Claesson and N. A. Hillarp, Acta Physiol. Scand., 13, 115-129 (1947). 



3« C. E. Bills, J. Am.. Med. Assoc, 110, 2150-2155 (1938). 



3« F. E. Kendall, E. H. Mosbach, L. L. Abell, and W. Meyer, Federation Proc, 12, 

 449 (1953). 



