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GH-releasing factor (GRF)-stimulated GH release is dependent on a biphasic increase in free intracellular Ca2+ concentration [( Ca2+]i), resulting from an influx of Ca2+ into somatotrophs, while the inhibitory action of somatostatin (SRIF) on basal and GRF-induced GH release results from its ability to lower [Ca2+]i by inhibiting Ca2+ influx. This study was(More)
This study was carried out to investigate the role of free intracellular Ca2+ ([Ca2+]i) in the action of GH-releasing factor (GRF) by determining whether GRF causes and increase in [Ca2+]i and whether this increase results from changes in Ca2+ influx/efflux and/or mobilization of intracellular Ca2+ stores. We used a purified preparation of normal rat(More)
This study was carried out to investigate the role of Ca2+ in the somatostatin (SRIF)-induced inhibition of GH release. We examined the effect of SRIF on basal and GH-releasing factor (GRF)-induced increases in Ca2+ influx and free intracellular Ca2+ concentration ([Ca2+]i) in normal somatotrophs and examined the effect of SRIF on 45Ca uptake, [Ca2+]i(More)
A hybrid nonlinear regression (NLR) model and a neural network (NN) model, each designed to forecast next-day maximum 1-hr average ground-level O3 concentrations in Louisville, KY, were compared for two O3 seasons--1998 and 1999. The model predictions were compared for the forecast mode, using forecasted meteorological data as input, and for the hindcast(More)
The purpose of this study was to investigate the involvement of protein kinase C in growth hormone-releasing factor (GRF) action by directly measuring the effect of GRF on protein kinase C activity in purified male rat somatotrophs. Somatotrophs were incubated with GRF (10(-7) M) for 0.33, 1, 3, 10, 30 and 90 min. Protein kinase C present in soluble and(More)
We examined the effect of the voltage-sensitive Ca2+ channel antagonists, diltiazem and nifedipine, on basal and stimulated growth hormone (GH) release from purified somatotrophs. Our aim was to ascertain whether an influx of Ca2+ from the extracellular to the intracellular compartment is essential for augmented release. Basal release was decreased in a(More)
The purpose of this study was to characterize the adenylate cyclase system in a purified population of normal somatotrophs derived from rat pituitary and to determine the responses of this system to GRF, somatostatin, guanine nucleotides, and cations. Additionally, experiments were performed to evaluate the interrelationships among changes in adenylate(More)
To examine the role of protein kinase-C in the mediation of GH release we used acutely dispersed purified somatotrophs in static incubation and acutely dispersed adenohypophyses in perifusion. In static incubation, activation of protein kinase-C by phorbol 12-myristate 13-acetate (PMA) and 1,2-dioctanoyl-rac-glycerol (diC8) resulted in an increase in GH(More)
The purpose of this study was to characterize the biological activity of the synthetic rat growth hormone releasing factor analogue rGRF(1-29)NH2 and to compare its action on growth hormone (GH) release to that of authentic rGRF(1-43)OH. We first compared the concentration-response characteristics of the two peptides in static incubation, and then examined(More)
We studied the role of the phosphatidylinositol system in the action of growth hormone-releasing factor (GRF). We asked whether GRF stimulates the activity of phospholipase C by determining GRF-induced changes in 32P labeling of the individual phosphoinositides and inositol phosphates in purified rat somatotrophs. The somatotrophs were challenged with GRF(More)