Periovulatory changes in catfish ovarian oestradiol-17beta, oestrogen-2-hydroxylase and catechol-O-methyltransferase during GnRH analogue-induced ovulation and in vitro induction of oocyte maturation by catecholoestrogens

Abstract

In the catfish Heteropneustes fossilis and Clarias batrachus, ovarian oestrogen-2-hydroxylase (OE-2-H) activity increased significantly at 8 h after the injection of an ovulatory dose (0·15 µg/g body weight) of a mammalian GnRH analogue ([-Ala 6 -Pro 9 ]-LHRH ethylamide) and was restored to the 0 h (control) level after egg-stripping at 16 h. On the other hand, ovarian oestradiol-17 (OE 2 ) level and catechol-O-methyltransferase (COMT) activity decreased significantly at 8 h. While the OE 2 level was restored to the 0 h level, COMT activity increased significantly at 16 h. Changes in ovarian OE 2 level and enzymes indicate higher synthesis of 2-hydroxylated catecholoestrogens and their degradation during the periovulatory period. Under in vitro conditions, the synthetic catecholoestrogens (CEs, 2-and 4-hydroxylated oestradiol-17 and oestrone (OE 1 )) induced germinal vesicle break down (GVBD) in a dose-(0·01-10 µg/ml) and duration-(1-36 h) dependent manner, the mean values of the responses being in the order 2-OH OE 2 >4-OH OE 2 > 2-OH OE 1 >4-OH OE 1 . The CE-induced GVBD response (8 h induction) was not blocked by prior and subsequent incubations with steroid synthesis inhibitors (cyanoketone, epostane and aminoglutethimide) up to 36 h, suggesting that de novo steroidogenesis is not essential for the response. The percentage of GVBD response to 2-h induction by CEs was significantly inhibited by actinomycin D (a transcriptional inhibitor) and cycloheximide (a translational inhibitor), indicating the involvement of both RNA and protein synthesis. The CE-induced 8-h stimulation of GVBD was mildly blocked by propranolol, the -adrenergic inhibitor, suggesting the response was partly mediated through a -adrenergic receptor mechanism. Incubations with phentolamine, an -adrenergic inhibitor, did not interfere with the CE-induced GVBD response. The results demonstrate CE-related enzymatic changes in teleost (catfish) ovaries and maturation-inducing substance activity of CEs.

A role for cytochrome P450 17α-hydroxylase/c17-20 lyase during shift in steroidogenesis occurring in ovarian follicles prior to oocyte maturation

“…In vitro oocyte maturation studies were carried out by killing the fish (decapitation) and about 100 oocytes with centrally located germinal vesicles were incubated in triplicate in catfish oocyte incubation medium [28] with 100 IU/ml of hCG (Pubergen, Uni-Sankyo, Hyderabad, India). Controls were treated with saline.…”

2-hydroxyestradiol-17β-induced oocyte maturation: involvement of cAMP–protein kinase A and okadaic acid-sensitive protein phosphatases,and their interplay in oocyte maturation in the catfishHeteropneustes fossilis

“…Estrogens are poor inducers of oocyte maturation but a recent report (Tokumoto et al, 2004) shows that the synthetic oestrogen diethylstilbestrol induces oocyte maturation in a manner similar to17,20␤-DP. Recently, we have shown that the hydroxy-and methoxy-metabolites of estrogens along with their synthesizing enzymes (estrogen-2-hydroxylase and catechol-O-methyltransferase, respectively) occur in catfish ovary and that the hydroxyestrogens elicit varying degrees of maturational activity (Senthilkumaran and Joy, 2001;Mishra and Joy, 2006a;Mishra and Joy, 2006b). The MIS-like activity of 2-hydroxyestradiol-17␤ (2-OHE 2 ) has been attributed to an indirect action through follicular steroidogenesis notably by the production of 17,20␤-DP (Mishra and Joy, 2006c).…”

Expression and polymorphism of farnesoic acid O-methyltransferase (FAMeT) and association between its SNPs and reproduction-related parameters of the giant tiger shrimp Penaeus monodon

“…The sequential physiological events of vitellogenesis, final maturation and ovulation during oogenesis are under the differential control of regulatory mechanisms (Huberman, 2000;Meusy and Payen, 1988;Senthilkumaran and Joy, 2001). Two different ORFs corresponding to PmFAMeT-l and PmFAMeT-s were obtained but only the recombinant PmFAMeT-l was produced in vitro.…”