Leucine aminopeptidase (LAP) activity and sexual dimorphism in rat exorbital lacrimal gland.

Leucine amonopeptidase (LAP) activity was histochemically studied in the rat exorbital lacrimal gland. The enzyme is present in the secreting cells of both male and female prepuberal rats, in vivo and in monolayer cultures, while in the adult rat it is demonstrable only in the female. Furthermore, LAP is influenced by the sex hormones, disappearing in the female gland after testosterone treatment and appearing in the adult male gland after administration of estradiol or cyproterone acetate. These results show that the behaviour of LAP can be considered as another character of sexual dimorphism of the rat exorbital gland. Furthermore, our findings, showing an inverse relationship between LAP activity and the PAS positivity of the secretion products, suggest the hypothesis that the presence of this exopeptidase could induce qualitative modifications of one or more secreted glycoprotein.