Changes in nitric oxide (NO) synthase isoforms and NO in the ovary of Heteropneustes fossilis (Bloch.) during the reproductive cycle

Abstract

The purpose of the study was to demonstrate the presence of nitric oxide (NO) synthase (NOS) isoforms (neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS)) and the role of NO in the ovary of Heteropneustes fossilis. In one half of the ovary collected during different reproductive stages, NOS isoforms were localized immunohistochemically in paraffin sections whereas the other half was processed for NOS and NO quantification using western blot followed by densitometry and nitrate/nitrite assay respectively. The role of NO on oocyte maturation was studied by examining the effect of NO donor (sodium nitroprusside; SNP) and NOS inhibitor (Nu-nitro-L-arginine methyl ester) on 17a,20b-dihydroxy-4-pregnen-3-one (17a,20b-P)-induced germinal vesicle breakdown (GVBD) in the cultured oocyte collected during prespawning phase. NOS immunostaining was predominantly localized in previtellogenic follicles, with nNOS detected in the nucleus and cytoplasm of oocytes whereas iNOS and eNOS localized in granulosa, theca cells, and cytoplasm of oocytes. The NOS expression was higher in previtellogenic phase when compared with vitellogenic phase. The nitrate/nitrite concentrations in ovary showed gradual increase from recrudescence (4 . 9G 0 . 19 nM/mg protein) to late previtellogenic phase (7 . 02G 0 . 53 nM/mg protein), but showed a sharp decline during the vitellogenic phase (0 . 41G0 . 053 nM/mg protein). Serum and ovarian nitrate/nitrite level showed a close association during the reproductive cycle. The results showed an increase in NOS activity and nitrate/nitrite concentrations as the follicle grow suggesting involvement of NO in follicular development. SNP significantly inhibited 17a,20b-P-induced GVBD in fish oocytes. Thus, it is concluded that the fish ovary possesses NOS/NO system and a possibility that NO has a role in follicular development and regulation of oocyte maturation in fish, H. fossilis.

Effects of Hypoxia Exposure on Hepatic Cytochrome P450 1A (CYP1A) Expression in Atlantic Croaker: Molecular Mechanisms of CYP1A Down-Regulation

“…2A ). The eNOS antibody has been validated in teleost ovaries previously [54]. Membranes were then washed with TBS-T, incubated for 2 h with anti-mouse IgG HRP-linked secondary antibody (1∶5,000; catalog no.…”

Thyroid hormones alter estrous cyclicity and antioxidative status in the ovaries of rats

“…Two isoforms are expressed constitutively, including neuronal NOS (nNOS) and endothelial NOS (eNOS), which can also be called constitutive NOS (cNOS); and another one is inducible under pathological conditions and inflammation, called inducible NOS (iNOS) (van Nassauw et al . ; Tripathi & Krishna ; Zheng et al . ).…”

Features of nitrogen metabolism in fishes

“…In fish of NO has important regulatory functions, taking part in the management of the cardiovascular system (Hansen and Jensen 2010;Pedersen et al 2010), the homeostatic functions of the gill apparatus (Jensen 2007;Cossins et al 2009), the activity of the cytochrome electron transport chain of mitochondria (Jensen 2007), the reproductive system of fish (Tamanini et al 2003;Tripathi and Krishna 2008). In turn, the process of NO synthesis is regulated by specific enzymatic complexes of NO-synthase, using as a substrate amino acid L-arginine.…”

“…In our opinion, should also be noted that the sharp surge in activity intraorganic arginine-dependent NO synthesis can cause growth intraorganic and systemic concentration of endogenous nitrite in fish. In particular, at certain stages of maturation of oocytes recorded a significant increase in the concentration of nitrite and nitrate anions in the tissues of the gonads and blood plasma of fish (Tripathi and Krishna 2008). The authors cited sources that the dynamics of concentrations of chemically stable metabolites of NO in the ovarian tissue of fishes, reaches a maximum phase previtellogenesis, however, sharply declining in the phase of vitellogenesis, on the one hand points to the important role of NO in the control of reproductive functions of fish, but with On the other hand, is quite reliable marker of oogenesis in fish.…”

“…Experimentally confirmed the possibility of using fish of exogenous nitrite as substrates in reactions resynthesis NO. However, attention is drawn to the following pattern-the authors of most-cited publications recognize that normally the content in the extracellular fluid of fish physiologically active metabolites of NO-endogenous nitrite is constant (Jensen 2007;Tripathi and Krishna 2008;Cossins et al 2009;Jensen and Rohde 2010). Taking note of the reasoned reviewed publications in the importance of the physiological role of nitrite to fish, the existence of specific mechanisms that determine their kinetics in the body, and narrow ranges of concentration in the extracellular fluid, it can be assumed that normally the level of nitrite is a physiological constant.…”