TRANSFERRIN BINDS SPECIFICALLY TO PACHYTENE SPERMATOCYTES

Abstract

We have examined the secretion and binding of transferrin to rat testicular cells. The only testicular cells found to secrete transferrin were the Sertoli cells (control 549 ± 6; FSH 1020 ± 17 ng/day · 106 cells, mean ± SEM). The Sertoli cells also contained specific binding sites for transferrin with a Kd of 2.0 × 10−9M. Of the other testicular cells examined only fractions rich in pachytene spermatocytes possessed specific trans-ferrin-binding sites. Late pachytene spermatocytes (97% pure) bound [125I]iodotransferrinwith a similar affinity as Sertoli cells (Kd 1.7 × 10−9M). Fractions of early and mid pachytene spermatocytes contained trans-ferrin-binding sites with a higher affinity (Kd 0.3 × 10−9M). This is the first report of a protein that has specific binding sites on germ cells.