Glycohistochemical investigation of canine and feline zonae pellucidae of preantral and antral oocytes

Glycoconjugate modifications were analysed in the zona pellucida during dev elopment of oocytes in dog and cat using conventional histochemical stainin g methods with or without previous carbohydrate digestion. A series of lect ins combined with desulphation and sialic acid degradation were applied. No differences were observed between dog and cat follicles using conventional histochemical staining methods. In both species, the zona pellucida and fo llicular fluid/intercellular matrix strongly reacted with PAS and high iron diamine stain (HID) and reacted moderately with low iron diamine stain (LI D). Treatment with testicular hyaluronidase, chondroitinase ABC, chondroiti nase AC and chondroitinase B treatment diminished HID and LID positivity of follicular fluid and intercellular matrix. Lectins that gave the most inte nse staining of the zona pellucida of both species were SEA, PNA, RCA-I, GS A-IB4 and WGA, indicating the presence of beta-D-GalNAc, D-Gal and GlcNAc r esidues. Sulpho- and asulpho-carbohydrates were identified in terminal and/ or subterminal positions linked to sialic acid residues. In conclusion, the results indicate that glycosaminoglycans are not present in the zona pellu cida of both species. Differences were observed in carbohydrate residues an d in their spatial distribution, depending on species and developmental sta ge of the follicles. The similarity in lectin affinity between ooplasm and zona pellucida of oocytes present in follicles at different stages of devel opment confirm the involvement of oocytes in zona pellucida production.