Steroid effects on the in vitro LH secretion from pituitary cells of sexually immature carp (Cyprinus carpio L.) under the influence of naltrexone and morphine

Abstract

Dispersed cells from sexually immature carp (footlings) pituitaries were exposed to estradiol (E<sub>2</sub>) or testosterone (T) (both at 3 × 10<sup>–8</sup> M) in the presence of opioid receptor antagonist naltrexone (10<sup>–8</sup> or 10<sup>–6</sup> M) and/or agonist – morphine (10<sup>–8</sup> or 10<sup>–6</sup> M). Naltrexone alone at 10<sup>–6</sup> M increased the LH level as compared with the control. Morphine (10<sup>–8</sup> or 10<sup>–6</sup> M), T and E2 had no influence on LH levels. The combination of T with naltrexone (10<sup>–8</sup> M) stimulated LH release if compared with the control or with T alone. Morphine (both concentrations) with T caused significantly higher LH secretion than the control medium and T alone. Estradiol with naltrexone (10<sup>–8</sup> and 10<sup>–6</sup> M) had no influence on LH concentration. In media with E2 and morphine (10<sup>–8</sup> M) LH levels were higher than in the control and estradiol alone. The results show that in common carp sex steroids affect the response of pituitary cells to opioid agonist or antagonist giving an evidence on the role of steroids in LH release mediated by the opioid system.

Interaction of ghrelin and opioids in luteinizing hormone (LH) secretion by pituitary cells of common carp, <I>Cyprinus carpio</I> (Actinopterygii: Cypriniformes: Cyprinidae), cultured in vitro

“…3, 4). These in vitro effects of ghrelin on LH secretion in female and male carp have already been described by Sokolowska-Mikolajczyk et al (2009). also observed stimulatory influence of ghrelin in goldfish pituitary cell incubation system, but with a 100 times lower dose than in our experiment.…”

“…The most important factors that received the most attention are gonadotropin-releasing hormone and dopamine, which inhibits gonadotropin release (Chang and Peter 1983, 1984, Peter et al1986. Other factors like norepinephrine, g-amino butyric acid, melatonin, neuropeptide Y, cholecystokinin (Van der Kraak et al 1998), opioids (Cheng unpublished * ) Rosenblum and Peter 1989, Sokolowska-Mikolajczyk et al 2002a, b, 2005, ghrelin (Unniappan et al 2002, Sokolowska-Mikolajczyk et al 2009) and leptin (Peyon et al 2001, Weil et al 2003 are also involved in the regulation of gonadotropin secretion. They can act directly at the level of the pituitary gonadotrophs, but also by the modulation of GnRH and dopamine secretion from the hypothalamus.…”

“…The in vivo experiments conducted on goldfish and common carp demonstrated the involvement of opioids or ghrelin in gonadotropin release, but they failed to identify the exact site of their action (Rosenblum and Peter 1989, Sokolowska-Mikolajczyk et al 2002a,b, Unniappan and Peter 2005. The in vitro approach demonstrated that both peptides act directly on gonadotrophs of goldfish and common carp (Sokolowska- Mikolajczyk et al 2002a, b, Socha et al 2003, Sokolowska-Mikolajczyk et al 2005, 2009). The present work investigated the interaction of opioids with ghrelin, because ghrelin is implicated in the regulation of opioid release in mice (Pierzchała-Koziec et al 2006).…”

“…The experiment was conducted on sexually mature common carp, Cyprinus carpio L., in June 2005. Because one part of this experiment concerning the spontaneous and sGnRH-analogue-stimulated LH release under the influence of ghrelin has already been published (Sokolowska-Mikolajczyk et al 2009), the control values are the same for both reports. Eight females and 10 males weighing an average of 1.95 ± 0.30 and 1.46 ± 0.06 kg, respectively were netted from the outdoor ponds of the Fishery Station belonging to the Department of Ichthyobiology and Fisheries, University of Agriculture in Krakow, Poland.…”

“…In primates, sheep, and rats ghrelin has an inhibitory impact on the reproductive system (Furuta et al 2001, Vulliémoz et al 2004, Fernandez-Fernandez et al 2006, Iqbal et al 2006. In fish, like in mammals, ghrelin controls food intake and regulates the release of pituitary hormones (GH and LH) (Unniappan et al 2002, 2004, Sokolowska-Mikolajczyk et al 2009). Limited data on the role of ghrelin in sexual maturation or reproduction of fish show that, unlike in mammals, ghrelin stimulates LH release, acting directly on the pituitary (Grey andChang 2008, Sokolowska-Mikolajczyk et al 2009) and/or at the level of hypothalamus .…”