Effects of a nitric oxide donor and nitric oxide synthase inhibitors on luteinizing hormone-induced ovulation in the ex-vivo perfused rat ovary

Abstract

The aim of this study was to investigate the role of nitric oxide (NO) in ovulation and ovarian steroidogenesis by the use of NO synthase (NOS) inhibitors and an NO donor administrated to the luteinizing hormone (LH)-stimulated ex-vivo perfused pre-ovulatory rat ovary. The ovaries were stimulated with LH (0.2 microgram/ml) alone or in combination with the phosphodiesterase inhibitor IBMX (200 micromol/l). The presence of both endothelial NOS (eNOS) and inducible NOS (iNOS) in the perfused rat ovary were detected by immunoblotting and a clear increase in amount of iNOS protein was seen after LH+IBMX stimulation. The addition of a non-selective NOS inhibitor, N(G)-monomethyl-L-arginine (L-NMMA; 300 micromol/l), to the perfusate significantly decreased ovulation numbers (median = 4. 0, range = 1-14) as compared with LH + IBMX stimulated control (12.0, 6-17). In contrast, an inhibitor with relative selectivity towards iNOS, aminoguanidine bicarbonate (AG, 300 micromol/l and 1 mmol/l), did not change the ovulation rate (11.5, 6-18 and 11.0, 7-15 respectively). In perfusions with only LH, a lower ovulation rate was seen but with similar effects (0.0, 0-8 for L-NMMA; 7.5, 3-12 for control and 7.0, 1-15 for AG 300 micromol/l). The administration of an NO donor, spermine NONOate, resulted in similar ovulation numbers as in LH-stimulated controls. The NO inhibitors did not affect steroid concentrations in the perfusion media, while 100 micromol/l NONOate increased progesterone production.

Característica histológica, ultra-estrutural e produção de nitrito de folículos pré-antrais caprinos cultivados in vitro na ausência ou presença de soro

“…Quanto ao desenvolvimento folicular, o NO tem sido considerado um potencial regulador, pois está envolvido em várias funções fisiológicas no ovário, incluindo a ovulação e a esteroidogênese (Matsumi et al, 1998a;Mitsube et al, 1999). Estudos mostraram que a óxido nítrico sintetase indutora (iNOS), uma das enzimas responsáveis pela síntese de NO, tem sido predominantemente localizada nas células da granulosa de grande parte do folículos antrais imaturos normais, enquanto as células da granulosa de folículos antrais maturos normais ou de folículos atrésicos são desprovidas dessa enzima (Matsumi et al, 1998a,b …”

Cyclic GMP Signaling Is Involved in the Luteinizing Hormone-Dependent Meiotic Maturation of Mouse Oocytes1

“…Furthermore, LH still causes a decrease in cGMP in the presence of PDE5 inhibitors, further excluding the possibility that LH acts through activation of a cGMP-PDE. In several species, LH modulates NO production [23,44,45], which may in turn modulate guanylate cyclase activity [42]. Therefore, it is possible that the mechanism by which LH regulates cGMP in the mouse POF is via the NO-guanylate cyclase pathway.…”

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

“…In rat ovary, expression of eNOS increases after LH surge (Zackrisson et al 1996, Jablonka-Shariff & Olson 1997, and eNOS-derived NO stimulates ovulatory process (Jablonka-Shariff & Olson 1998, Mitsube et al 1999. The changes in iNOS expression during ovulatory process are controversial (Jablonka-Shariff & Olson 1997, Matsumi et al 2000.…”