|Role of cyclic AMP-dependent protein kinase (PKA) in regulating egg-laying hormone (ELH) secretion from Aplysia bag cells|
Wayne, N.L. (1994). Role of cyclic AMP-dependent protein kinase (PKA) in regulating egg-laying hormone (ELH) secretion from Aplysia bag cells. Neth. J. Zool. 44(3-4): 588-598
In: Netherlands Journal of Zoology. E.J. Brill: Leiden. ISSN 0028-2960, more
The aim of the present work was to generate information that allows further exploration of mechanisms regulating release of egg-laying hormone (ELH) from neuroendocrine bag cells of Aplysia. To start, experiments that document the pattern of ELH secretion in response to an electrical afterdischarge from excised neural preparations maintained in vitro, as well as from freely-behaving animals are described. Preliminary studies investigating the role of the cAMP second- messenger system in regulating ELH secretion are also discussed.Concentrations of ELH, from either medium (in vitro preparations) or hemolymph (in vivopreparations), we measured by radioimmunoassay. In both types of preparations, the electical afterdischarge triggered ELH secretion, but peak levels were reached near the end of or following termination of the afterdischarge.All preparations showed prolonged durations of secration that extend a least 43 min at the end of the afterdischarge, indicating that action potentials are not required for maintening secretion of ELH.What cellular processes regulate this prolonged secretion? The cAMP second-messenger system is a likely candidate because of its suggested role in excitation of bag-cell membrane and transport of secretory granules to bag-cell growth cones in culture. Treatment with the specific cAMP-dependent protein kinase (PKA) inhibitor Rp-cAMPS attenuated the amplitude and duration of ELH secretion whereas the PKA stimulator Sp-cAMPS had no significant effects on secretion compared to untreated controls. These preliminary suggest that: 1) PKA plays an important role in regulating ELH release; 2) Afterdischarge-induced PKA maximally stimulates ELH release such that further evaluations in PKA do not enhance secretion.