Substance P- and neuron-specific enolase-like immunoreactivity of rodent Leydig cells in tissue section and cell culture.

Comparative immunocytochemical studies concerning the presence of a neurotransmitter (substance P), and a marker of neuroendocrine cells (neuron-specific enolase), in the Leydig cells of 3 mammalian species (golden hamster, guinea pig, and rat) were carried out on tissue sections and cell cultures. Substance P(SP)-like immunoreactivity (-LI) was found to be present in both fetal and adult generation of Leydig cells in hamster and guinea pig, while neuron-specific enolase (NSE)-LI was detected in Leydig cells of the 3 species at all stages studied: fetal, neonatal and adult. In primary cultures of Leydig cells isolated from adult hamster testes, SP- and NSE-LI was also established. This result was considered as an indirect evidence for the synthesis of the substances under study by the steroidogenic cells of the testis. A comparison of these results with data obtained in vivo suggests that Leydig cells may be related to the APUD- or the diffuse neuroendocrine system.