Study in vitro of the phagocytic function of Sertoli cells in the rat.

Aspects of the interaction between residual bodies/cytoplasts from elongated spermatids (RB/CES) and Sertoli cells were studied in vitro. Highly enriched Sertoli cells (91%: experiment A), very highly enriched Sertoli cells (greater than 96%: experiment B), as well as peritubular cells were isolated from testes of 20-day-old rats by means of hypotonic treatment. Isolated Sertoli cells and peritubular cells were also prepared from 45-day-old rats (experiment C). RB/CES were isolated by centrifugal elutriation from testes of rats aged 90-120 days. The kinetics of adhesion of RB/CES to Sertoli cells were similar in all experiments. FSH accelerated binding of RB/CES but markedly reduced the number of RB/CES phagocytosed. Co-culture of the highly enriched Sertoli cells from experiments A and C with isolated peritubular cells did not change the kinetics of adhesion of RB/CES. However, when the contamination of Sertoli cells by peritubular cells was at a minimum (experiment B), addition of peritubular cells induced a slight but significant stimulation of the binding of RB/CES. Transmission electron microscopy revealed the following events within 24 h of co-culture: adhesion of the RB/CES to microvilli of Sertoli cells; internalization of RB/CES; lysis of the membrane of RB/CES; total digestion. Therefore, FSH and peritubular cells modulate the interaction in vitro between Sertoli cells and RB/CES, and the different steps of residual body disposal can be reproduced in co-culture. The co-culture model described in this study provides a useful system for the study of phagocytic activity by Sertoli cells.