Sertoli cells and peritubular fibroblasts were collected from sexually mature Wistar rats and incubated by themselves (ASC) or in co-culture (AS/PC) for ten days with or without follicle stimulating hormone (FSH). Freshly collected cells and those of the ASC and AS/PC cultures were processed for histochemical detection of three esterases and four dehydrogenases. The relative staining intensities of azo dye and formazan reaction products were recorded for the cell cultures, co-cultures and appropriate controls. Freshly collected Sertoli cells stained heavily for lactic dehydrogenase (LDH), succinic dehydrogenase (SDH), glucose-6-phosphate dehydrogenase (G-6-PDH), non-specific esterase (Est.) and 3 beta-hydroxysteroid dehydrogenase (3 beta-OLDH). For Sertoli cells alone in culture (ASC) there was a marked decline of enzyme reaction product deposition/cell for LDH and Est. and absence of cellular staining for SDH, G-G-PDH, B-Est. and 3 beta-OLDH. The addition of FSH did not change this histochemical staining pattern for the adult cells in vitro. The presence of peritubular cells in adult Sertoli cell cultures (AS/PC) resulted in the maintenance of metabolic enzyme staining (i.e., LDH, SDH, G-6-PDH and Est.) in Sertoli cells, minimal staining for B-Est., but absence of detectable enzyme reaction product for 3 beta-OLDH. Sertoli cells co-cultured with other fibroblasts or in medium pre-conditioned with peritubular cells but not containing them stained minimally for LDH and Est. and did not generate reaction product for any of the other enzymes. The addition of FSH to the AS/PT co-culture as in the ASC cultures did not affect the enzyme histochemical staining profile of Sertoli cells.(ABSTRACT TRUNCATED AT 250 WORDS)