Actions of insulin and vitamin A on Sertoli cells

The synthesis of androgen-binding protein by cultured Sertoli cells is increased by insulin, retinol, follitropin and testosterone. Only follitropin will stimulate an increase in cyclic AMP in these cells, yet each agent individually increased the synthesis of androgen-binding protein in short-term cultures. For long-term culture of Sertoli cells follitropin, testosterone, insulin, and retinol appeared to act synergistically to prolong the ability of the cells to secrete androgen-binding protein. These are the first reported results which suggest an action of insulin and retinol directly on Sertoli cells even though the importance of both factors in male reproduction is known.