Multiplication stimulating activity (MSA) can substitute for insulin to stimulate the secretion of testicular transferrin by cultured sertoli cells

Both MSA and insulin were found to stimulate transferrin production in cultured Sertoli cells to the same extent in the absence or presence of follitropin, testosterone, or retinol. Sertoli cells were responsive to 30-fold lower concentrations of MSA than of insulin. MSA and insulin together stimulated transferrin secretion to the same extent as either hormone alone. These results, and what is presently understood about the relationship of MSA and insulin, suggest that insulin can substitute for the action of an MSA-like peptide in the stimulation of testicular transferrin secretion by Sertoli cells.