Section 8
Chapter 7,504

Lack of involvement of arachidonic acid metabolism in chicken gonadotropin releasing hormone ii cgnrh ii stimulation of gonadotropin secretion in dispersed pituitary cells of goldfish carassius auratus identification of a major difference in salmon gnrh and chicken gnrh ii mechanisms of action

Chang, J.P.; Wildman, B.; Van Goor, F.

Molecular and Cellular Endocrinology 79(1-3): 75-84


ISSN/ISBN: 0303-7207
Accession: 007503751

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Gonadotropin (GTH) release in static incubations of dispersed goldfish pituitary cells was stimulated by chicken GTH-releasing hormone II (cGNRH-II), salmon (s)GnRH, phospholipase A2, phospholipase C, phospholipase D, and arachidonic acid (AA). Coincubation with nordihydroguaiarectic acid (NDGA), 5,8,11,14-eicosatetraeonic acid, and indomethacin did not alter the GTH responses to cGnRH-II. In contrast, NDGA reduced sGnRH-stimulated GHT release. Incubation with Ca2+-deficient medium abolished the GTH responses to cGn-RH-II, reduced sGnRH-stimulated GHT release, but did not alter AA-actions on GTH secretion. Apomorphine, a dopamine agonists that had been shown to partially inhibit the GTH responses to sGnRH and to abolish those induced by cGn-RH-II, did not affect the hormone response to AA. However, the partial inhibitory actions of NDGA and apomorphine on sGnRH-induced GTH release was additive. These findings suggest the existence of a major difference in cGnRH-II and SGnRH stimulation of GTH release - AA metabolism is not involved in cGnRH-II, as opposed to sGnRH actions. This difference in second messenger activation may also explain the differential sensitivity of the two GnRH peptides to dopamine inhibition and manipulations of extracellular Ca2+ availability. The results further suggest that dopamine and AA affect GTH release via non-overlapping signal transduction pathways.

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