Sodium chlorate induces undersulfation of cellular proteoglycans and increases in FSH-stimulated estradiol production in immature rat Sertoli cells.

The functional influence of cell proteoglycan (PG) undersulfation on estradiol synthesis by immature rat Sertoli cell cultures was investigated by using sodium chlorate, an inhibitor of the active sulfate donor for sulfotransferases. The addition of sodium chlorate to 20-day-old rat Sertoli cell cultures abolished [35S]-sulfate incorporation into neosynthesized PG and consequently reduced the residence time of undersulfated PG in cell membrane. Simultaneously, follicle-stimulating hormone (FSH)-stimulated estradiol synthesis was increased by 45%. The effects of sodium chlorate upon Sertoli cell PG synthesis and steroidogenesis were not reproduced with the addition of sodium chloride. Addition of phosphodiesterase inhibitors (MIX or Ro20-1724) decreased the magnitude of the chlorate effect on FSH-stimulated steroidogenesis, suggesting that part of chlorate's effect on steroidogenesis resulted from a decrease in adenosine cyclic 3',5'-phosphate (cAMP)-specific phosphodiesterase activity. Additionally, chlorate 1) increased Sertoli cell steroidogenesis at a step located beyond cAMP (restricted to Sertoli cell cultures exhibiting moderate steroidogenic response to (Bu)2cAMP) and 2) abolished the inhibition of steroidogenesis induced by transforming growth factor-beta. These results support our previous data, which showed that alteration in PG synthesis and the consequent decrease in cell membrane PG content induce an increase in FSH-stimulated estradiol synthesis in Sertoli cell cultures. The identification of cAMP-specific phosphodiesterase activity as a signal transduction step modified by PG undersulfation suggests the possible involvement of cell PG in the regulation of phosphodiesterase activity and, therefore, of FSH responsiveness during testicular development.