ABSTRACT: Attempts have been made to confirm the suggestion that cholesterol can be metabolized to C19 steroids by cleavage of the C8 side-chain between C-17 and C-20. The evidence previously adduced for the existence of this pathway has come from in vitro incubation experiments in which [26-14C] cholesterol was used as the substrate for the formation of [14C]6-methylheptan-2-one. The identification of the C8 product was established by the reverse-isotope dilution technique. In this study, the procedures previously reported have been repeated and have been extended by the addition of several purification steps designed to validate the association of radio-carbon with this C8 moiety. In none of our experiments was it possible to prove unequivocally that [14C]6-methylheptan-2-one is formed from [26-14C]-cholesterol during incubation with tissues from a variety of steroid-producing glands. If the pathway, C27 → C19 + C8 exists, corroboration will have to come from other kinds of evidence.
Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism.