Functional interactions between vasotocin and prostaglandins during final oocyte maturation and ovulation in the catfish Heteropneustes fossilis

Functional interactions between vasotocin (VT) and prostaglandins (PGs) in the regulation of final oocyte maturation (FOM) and ovulation were investigated in the catfish Heteropneustes fossilis. Incubation of post-vitellogenic follicles with VT resulted in significant increases of both PGF(2 alpha), and PGE(2) at 8 and 16 h intervals. The rise was higher at 16 h except in the 1000 nM VT group, in which the PG levels decreased compared to the 100 nM group (biphasic effect). VT was more effective to increase the PG levels in comparison to hCG or IT. The co-incubation of the follicles with both hCG (20 IU/ml) and VT (100 nM) increased significantly PGF(2 alpha), level at 8 h, higher than that elicited by each when incubated alone. Pre-incubation of the follicles with V-1 receptor antagonist, alone or in co-incubation with VT, significantly inhibited the VT-stimulated PGF(2 alpha) and PGE(2) levels. Under similar conditions, V-2 receptor antagonist did not affect the PGE(2) levels. Both VT (100 nM) and PGs stimulated FOM (germinal vesicle breakdown) and ovulation in a dose- and duration dependent manner, PGF(2 alpha), was more effective. Incubation of postvitellogenic follicles with indomethacin (a non selective cyclooxygenase inhibitor) per se did not affect FOM and ovulation but significantly decreased VT and PG effects upon pre-incubation. The results suggest that the VT stimulation of PGs may be mediated mainly through the V-1 receptor though the involvement of V-2 receptor cannot be excluded. The article also discussed the positive interplay of gonadotropin, maturation-inducing steroid, VT and PG during FOM and ovulation. (C) 2013 Elsevier Inc. All rights reserved.