@article{hyde_seale_grau_borski_2004, title={Cortisol rapidly suppresses intracellular calcium and voltage-gated calcium channel activity in prolactin cells of the tilapia (Oreochromis mossambicus)}, volume={286}, ISSN={["1522-1555"]}, DOI={10.1152/ajpendo.00088.2003}, abstractNote={Cortisol was previously shown to rapidly (10-20 min) reduce the release of prolactin (PRL) from pituitary glands of tilapia ( Oreochromis mossambicus). This inhibition of PRL release by cortisol is accompanied by rapid reductions in45Ca2+and cAMP accumulation. Cortisol's early actions occur through a protein synthesis-independent pathway and are mimicked by a membrane-impermeable analog. The signaling pathway that mediates rapid, nongenomic membrane effects of glucocorticoids is poorly understood. Using the advantageous characteristics of the teleost pituitary gland from which a nearly pure population of PRL cells can be isolated and incubated in defined medium, we examined whether cortisol rapidly reduces intracellular free calcium ([Formula: see text]) and suppresses L-type voltage-gated ion channel activity in events that lead to reduced PRL release. Microspectrofluorometry, used in combination with the Ca2+-sensitive dye fura 2 revealed that cortisol reversibly reduces basal and hyposmotically induced [Formula: see text] within seconds ( P < 0.001) in dispersed pituitary cells. Somatostatin, a peptide known to inhibit PRL release through a membrane receptor-coupled mechanism, similarly reduces [Formula: see text]. Under depolarizing [K+], the L-type calcium channel agonist BAY K 8644, a factor known to delay the closing of L-type Ca2+channels, stimulates PRL release in a concentration-dependent fashion ( P < 0.01). Cortisol (and somatostatin) blocks BAY K 8644-induced PRL release ( P < 0.01; 30 min), well within the time course over which its actions occur, independent of protein synthesis and at the level of the plasma membrane. Results indicate that cortisol inhibits tilapia PRL release through rapid reductions in [Formula: see text] that likely involve an attenuation of Ca2+entry through L-type voltage-gated Ca2+channels. These results provide further evidence that glucocorticoids rapidly modulate hormone secretion via a membrane-associated mechanism similar to that observed with the fast effects of peptides and neurotransmitters.}, number={4}, journal={AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM}, author={Hyde, GN and Seale, AP and Grau, EG and Borski, RJ}, year={2004}, month={Apr}, pages={E626–E633} }
 @article{borski_hyde_fruchtman_2002, title={Signal transduction mechanisms mediating rapid, nongenomic effects of cortisol on prolactin release}, volume={67}, ISSN={["0039-128X"]}, DOI={10.1016/S0039-128X(01)00197-0}, abstractNote={While the mechanisms governing genomically mediated glucocorticoid actions are becoming increasingly understood, relatively little is known with regard to the cell signaling pathways that transduce rapid glucocorticoid actions. Studies of the cultured tilapia rostral pars distalis (RPD), a naturally segregated region of the fish pituitary gland that contains a 95–99% pure population of prolactin (PRL) cells and is easily dissected and maintained in a completely defined, serum-free media, indicate that physiological concentrations of cortisol rapidly inhibit PRL release. The attenuative action of cortisol on PRL release occurs within 10–20 min, is insensitive to the protein synthesis inhibitor, cycloheximide, and mimicked by its membrane impermeable analog, cortisol-21 hemisuccinate-conjugated bovine serum albumin (BSA). Cortisol and somatostatin, a peptide known to work through membrane receptors to inhibit PRL release, rapidly and reversibly reduces intracellular free Ca2+ (Cai2+), and inhibits 45Ca2+ influx and BAYK-8644 induced PRL release. Preliminary investigations show cortisol, but not somatostatin, suppresses phospholipase C (PLC) activity in PRL cell membrane preparations. In addition, cortisol and somatostatin reduce intracellular cAMP and membrane adenylyl cyclase activity. These findings indicate that the acute inhibitory effects of cortisol on PRL release occur through a nongenomic mechanism involving interactions with the plasma membrane and inhibition of both the Ca2+ and cAMP signal transduction pathways. Cortisol may reduce Cai2+ by inhibiting influx through L-type voltage-gated channels and possibly release through a PLC/inositol triphosphate sensitive intracellular Ca2+ pool. In addition, it is also likely the steroid inhibits adenylyl cyclase activity in events leading to reduced cAMP production and the subsequent release of PRL.}, number={6}, journal={STEROIDS}, author={Borski, RJ and Hyde, GN and Fruchtman, S}, year={2002}, month={May}, pages={539–548} }