A biochemical and quantitative electron microscope study on steroidogenesis in ovotestis and digestive gland of the pulmonate snail Lymnaea stagnalis

Abstract The steroidogenic activity of ovotestis and of digestive gland of the snail Lymnaea stagnalis was determined in vitro at 3-hr intervals during a 24-hr cycle by measuring the conversion of pregnenolone into progesterone. The percentage conversion varied during this cycle in both tissues. The highest values were measured from 2100 to 0300 hr. The ovotestis appeared to be responsible for the main part of this increase in percentage conversion. A distinct correlation was found between the diurnal activity of steroid-synthesizing enzymes and the extensiveness of the smooth endoplasmic reticulum in Sertoli cells carrying spermatids and in Sertoli cells after spermiation, indicating that it is probably the Sertoli cells, that are responsible for the production of these steroids. It is probable that the steroids synthesized in the gonad of basommatophoran snails have only a local hormonal effect.