Neutral sterols of rat epididymis: high concentrations of dehydrocholesterols in rat caput epididymidis

Phospholipids and sterols are known to have multiple functions in reproduct ive tissue of mammals. High concentrations of the cholesterol precursor des mosterol have been described in testis, epididymis, and spermatozoa of vari ous species. These findings and the recent discovery of some cholesterol pr ecursors as meiosis-activating sterols suggest important functions of chole sterol precursors in fertility. Many sterol intermediates appear from the 1 9-step conversion of lanosterol, the first sterol synthesized in the cascad e of cholesterol synthesis, to cholesterol, The biochemical basis of the ge netically inherited Smith-Lemli-Opitz syndrome has been described as a defe ctive conversion of 7-dehydrocholesterol to cholesterol, Since this discove ry, interest has focused on this special cholesterol precursor. Here, we re port high concentrations of 7- and 8-dehydrocholesterol in caput epididymid is and spermatozoa derived from caput epididymidis of Sprague-Dawley and Wi star rats, which comprised up to 30% of total sterols, In contrast to caput epididymidis, 7- and 8-dehydrocholesterol were barely detected in cauda ep ididymidis or testis, Desmosterol increased several times from caput to cau da epididymidis.jlr This is the first report of the natural appearance of h igh concentrations of dehydrocholesterols in mammalian tissue, and it under lines the putative importance of cholesterol precursors in reproductive tis sue.