GnRH signaling in goldfish pituitary cells.

In goldfish, maturational gonadotropin (GTH) and growth hormone (GH) release are stimulated by two native GTH-releasing hormones (sGnRH and cGnRH-II). Both GnRHs stimulate GTH and GH release via activation of phospholipase C, protein kinase C, Ca2+ entry through voltage-sensitive channels and calmodulin. However, sGnRH-induced GTH release also involves arachidonic acid and intracellular Ca2+ components absent from its action on GH, as well as from cGnRH-II action on GTH and GH secretion. The relative roles and interactions of these signaling pathways in mediating sGnRH and cGnRH-II action on acute and prolonged GTH and GH release are compared. How two GnRHs bind to similar receptors but induce similar and dissimilar transduction mechanisms in two cell types and within one cell type is unknown.