Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have investigated the effects of bafilomycin A1, a specific inhibitor of vacuolar type H(+)-ATPase, on the secretion and intracellular distribution of prolactin in cultured rat pituitary tumor cells (GH3 cells). Pulse-labeling the cells with L-[35S]methionine for 5 min and subsequently incubating in chase medium containing 1 microM bafilomycin A1 showed inhibition of basal secretion of labeled prolactin. The inhibition of the secretion by the drug was clearly observed when it was added within 7.5 min after the pulse-labeling, whereas inhibition was barely observed when added at 22 min. When the pulse-labeled cells were chased with 1 microM bafilomycin A1 for 1 h and then washed and incubated in the presence of 10 micrograms/ml brefeldin A (BFA) for 2 h, BFA barely affected the secretion during the latter 2 h period. This result suggested that the labeled prolactin had passed through a BFA-sensitive step(s) in the intracellular transport during the treatment with 1 microM bafilomycin A1. Immunofluorescence microscopy and immunogold electron microscopy revealed that, when the cells were incubated with 0.1 to 1.0 microM bafilomycin A1, small, dense secretory granules containing prolactin decreased markedly, and numerous large vacuoles appeared, which also contained prolactin, and were partially coated with clathrin-like materials. The Golgi apparatus itself was preserved except for some dilatation of the trans-Golgi cisternae and trans-Golgi network (TGN) where these vacuoles were likely to be formed. These results suggest that acidification in immature secretory granules generated by a vacuolar type H(+)-ATPase is necessary for the intracellular transport of prolactin, maturation and concentration processes of the secretory granules.
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PMID:Inhibition of intracellular transport of newly synthesized prolactin by bafilomycin A1 in a pituitary tumor cell line, GH3 cells. 826 70

Thyrotropin releasing hormone (TRH), which stimulates prolactin secretion, increases the fluorescence of cultured bovine anterior pituitary (bAP) cells in the presence of the non-permeant membrane indicator dye FM 1-43 [Stafford SJV. Shorte SL. Schofield JG. (1993) Use of a fluorescent dye to measure secretion from intact bovine anterior pituitary cells. Biosci. Rep., 13, 9-17]. FM 1-43 is non-fluorescent in aqueous solution but becomes fluorescent when incorporated into the plasma membrane. The membrane area accessible to FM 1-43 dye, and therefore cell fluorescence, increases during exocytosis as secretory granules fuse with the plasma membrane, and endocytosis as vesicles formed at the plasma-membrane fuse with intracellular organelle membranes. We have here measured changes in FM 1-43 uptake and the intracellular calcium concentration ([Ca2+]i) concurrently in the same cells on exposure to TRH, phorbol myristate acetate (PMA) or NH4Cl. TRH (0.1-10 microM) caused a transient increase in [Ca2+]i in 70-90% of bAP cells and in 60-90% of the responding cells also caused a sustained increased FM 1-43 fluorescence. TRH increased [Ca2+]i but did not affect FM 1-43 fluorescence in GH3 rat pituitary cells, probably because they contain too few secretory granules to give a detectable increase. The dopamine D2-receptor agonist quinpirole (10 microM) had little effect on the TRH-induced [Ca2+]i rise in bAP cells, but abolished the increase in FM 1-43 fluorescence. The phorbol ester PMA (0.3-3 microM) caused a small, transient increase in [Ca2+]i followed by a fall to levels lower than original resting levels in 40-60% of bAP cells and increased FM 1-43 uptake in cells showing these changes. Extracellular NH4Cl, which mobilises calcium from an ionomycin-insensitive calcium store, caused a transient [Ca2+]i increase in over 90% of the bAP-cells and increased FM 1-43 uptake in a subpopulation (> 50%) of these. The Na+/H+ ionophore monensin prevented the increase in FM 1-43 fluorescence but not the [Ca2+]i rise induced by TRH, prevented the increases in both FM 1-43 fluorescence and [Ca2+]i caused by NH4Cl, and reduced the number of cells showing a rise in FM 1-43 fluorescence in response to PMA from 64% to 34%. The Ca(2+)-ATPase inhibitor thapsigargin reduced the number of bAP cells displaying TRH-induced increases in [Ca2+]i and membrane-turnover from 74% to 18%, but did not affect the changes in [Ca2+]i or FM 1-43 fluorescence caused by PMA or NH4Cl. We discuss the relationships between the secretogogue-induced increases in FM 1-43 fluorescence and changes in intracellular [Ca2+]i under these conditions.
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PMID:Simultaneous measurement of [Ca2+]i and secretion-coupled membrane turnover, by single cell fluorescence microscopy. 858 72

Expression of the Na(+)-K(+)-ATPase alpha-subunit was investigated in the gill and trunk kidney of Salmo trutta. Groups of freshwater (FW) fish were treated with various hormones [cortisol: 3 x 4.0 micrograms/g; recombinant salmon growth hormone (rsGH): 3 x 0.25 micrograms/g; salmon prolactin (sPRL): 3 x 0.25 micrograms/g; recombinant bovine insulin-like growth factor-I (rbIGF-I): 2 x 0.01 micrograms/g; or 2 x 0.1 micrograms/g] or transferred to 25 parts per thousand seawater (SW) and sampled after 1, 2, 3, and 50 days. Total RNA was analyzed by Northern blotting using Xenopus laevis Na(+)-K(+)-ATPase alpha-subunit cDNA as probe. The probe detected a 3.8-kb transcript. Relative to untreated FW control fish, the abundance of alpha-subunit Na(+)-K(+)-ATPase mRNA in gill tissue increased 1.7-to 2.5-fold after treatment with cortisol, rsGH, and rbIGF-I and after transfer to SW. Na(+)-K(+)-ATPase enzyme activity was also significantly stimulated in these groups, except at 0.01 micrograms/g rbIGF-I. sPRL was without effect. In the kidney, alpha-subunit mRNA level and Na(+)-K(+)-ATPase activity were unaffected by hormone treatment and SW transfer. The results indicate that an increased abundance of alpha-subunit mRNA is part of the molecular mechanism behind the increased gill Na(+)-K(+)-ATPase activity induced by SW transfer, cortisol, GH, and IGF-I.
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PMID:Expression of Na(+)-K(+)-ATPase in the brown trout, Salmo trutta: in vivo modulation by hormones and seawater. 859 35

2',4'-dimethylbenzamilamiloride (DMB), a somewhat selective inhibitor of the Na(+)-Ca2+ exchanger, in concentrations of 10, 30 and 100 microM did not produce any significant effect on baseline prolactin release from anterior pituitary cells in primary culture. When prolactin secretion was stimulated by the inhibitor of the Na(+)-K(+)-ATPase, ouabain, that activates the Na(+)-Ca2+ exchanger as a Ca(2+)-influx pathway, DMB was able to produce inhibition of prolactin secretion. 5-(N,N-hexamethylene) amiloride (HMA), another amiloride analog which specifically inhibits the Na(+)-H+ antiporter and has no inhibitory activity on the Na(+)-Ca2+ exchanger, at the concentrations of 0.1, 1 and 10 microM, did not affect basal prolactin release whereas it significantly reduced prolactin release stimulated by thyrotropin releasing hormone (TRH) (1 microM). These results suggest that the Na(+)-Ca2+ antiporter is involved in the process of prolactin release elicited by the inhibition of the Na(+)-K(+)-ATPase whereas the Na(+)-H+ antiporter is involved in the prolactin secretion elicited by TRH.
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PMID:Role of the Na(+)-Ca2+ and Na(+)-H+ antiporters in prolactin release from anterior pituitary cells in primary culture. 878 11

The taurocholate (TC) maximal secretory rate (SRm) in the isolated perfused liver is increased in postpartum rats and ovariectomized rats treated with ovine prolactin (oPRL). The present studies were designed to characterize the mechanism(s) by which oPRL increases TC transport in the liver. oPRL (300 micrograms/day i.v. for 7 days) increased the SRm 1.6-fold from 185 to 364 nmol.min-1.mg protein-1 in the perfused rat liver and the maximal rate of transport for ATP-dependent transport 1.7-fold from 66 to 109 nmol.min-1.mg protein-1 in canalicular liver plasma membrane (cLPM) vesicles without changing the Michaelis constant (5-6 microM). The oPRL-mediated increases in biliary excretion in the perfused liver and ATP-dependent TC transport in cLPM vesicles were significantly inhibited by cycloheximide treatment (2 mg/kg). oPRL (300 micrograms/day iv for 7 days) increased expression of Ca(2+)-Mg(2+)-ecto-adenosinetriphosphatase mRNA sixfold and increased protein expression two- to threefold, but had no effect on the expression of P-glycoprotein (mdr1b and mdr2) mRNA. Thus the increase in ATP-dependent transport in cLPM vesicles due to oPRL treatment accounts for the increased TC SRm in the perfused liver. The oPRL-mediated increased TC transport may be associated with increased expression of proteins related to bile acid transport.
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PMID:Prolactin increases ATP-dependent taurocholate transport in canalicular plasma membrane from rat liver. 903 75

It is increasingly clear that growth hormone (GH) has growth-promoting effects in fishes, which are mediated in part by the insulin-like growth factor (IGF)-I. Growth-promoting actions of prolactin (PRL) have been reported in higher vertebrates, but are less well established in teleosts. We examined the effects of injecting homologous GH or the two homologous tilapia PRLs (tPRL177 and tPRL188) on the in vitro incorporation of [35S] sulfate (extracellular matrix synthesis) and [3H]thymidine (DNA synthesis) by ceratobranchial cartilage explants and on IGF-I mRNA levels in tilapia liver. Tilapia GH (tGH) and tPRL177 stimulated sulfate uptake at the highest doses examined. Thymidine incorporation was stimulated by tPRL177. tPRL188 was without these effects. Consistent with its somatotropic actions, tGH elevated IGF-I mRNA levels in the liver. tPRL177 also elevated liver IGF-I levels. Consistent with the previously described osmoregulatory actions of GH and PRL in teleosts, we observed that tGH elevated and tPRL177 and tPRL188 lowered levels of gill Na+,K+-ATPase activity. High-affinity, low-capacity binding sites for tGH in the tilapia liver were identified. tPRL177 binds with lower affinity than tGH to these sites but can displace 125I-labeled tGH from its receptor. The ability of tPRL177 to displace tGH was similar to that of ovine GH. tPRL188 did not displace 125I-labeled tGH binding. Collectively, this work suggests that tPRL177 may possess somatotropic actions similar to tGH, but only in freshwater tilapia where tPRL177 levels are sufficiently high for it to act as a competitive ligand for GH receptors.
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PMID:Somatotropic actions of the homologous growth hormone and prolactins in the euryhaline teleost, the tilapia, Oreochromis mossambicus. 905 Sep 6

To date, growth hormone (GH) is known to contribute to seawater adaptation only in salmonid fishes (primitive Euteleostei). Accordingly, the effects of homologous GH and two forms of homologous prolactin (PRL177 and PRL188) on hypoosmoregulatory ability and gill Na+,K(+)-ATPase activity in a more advanced euryhaline cichlid fish, the tilapia (Oreochromis mossambicus), were examined. Following adaptation of hypophysectomized fish to 25% seawater for 3 weeks, fish were given four injections of hormone or vehicle. They were then exposed to 100% seawater for 12 hr and examined for changes in plasma osmolality. Tilapia GH (0.02 and 0.2 microgram/g) significantly improved the ability of tilapia to decrease plasma osmolality following transfer to full-strength seawater, in a dose-related manner. Growth hormone treatment also significantly stimulated gill Na+,K(+)-ATPase activity (0.5 microgram/g). Both tilapia PRLs (PRL177 and PRL188) increased plasma osmolality in 100% seawater and reduced gill Na+,K(+)-ATPase activity, the effects induced by PRL188 being more significant than those by PRL177. Thus, GH may be involved in seawater adaptation of tilapia, a species belonging to the most advanced teleost super-order (Acanthopterygii), whereas both PRLs in tilapia are not involved in seawater adaptation.
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PMID:Osmoregulatory actions of growth hormone and prolactin in an advanced teleost. 912 69

We tested the hypothesis that nutritional state affects seawater acclimation by transferring either fed or food-deprived (2 weeks) male tilapia (Oreochromis mossambicus) from fresh water to full-strength sea water. Food-deprivation resulted in a significant increase in plasma concentrations of Na+, Cl-, cortisol, glucose, total amino acid, glutamate, serine and alanine, and in hepatic pyruvate kinase (PK) and lactate dehydrogenase (LDH) activities, whereas the prolactin-188 to prolactin-177 ratio (tPRL188:tPRL177) and plasma prolactin-188 (tPRL188), lactate, arginine and hepatic glycogen content and hepatic alanine aminotransferase (AlaAT) and 3-hydroxyacyl-Coenzyme A dehydrogenase (HOAD) activities were lower than in the fed group. Seawater transfer significantly increased the tPRL188:tPRL177 ratio and plasma concentrations of Na+, Cl-, K+, growth hormone (GH), glucose, aspartate, tyrosine, alanine, methionine, phenylalanine, leucine, isoleucine and valine levels as well as gill Na+/K+-ATPase activity and hepatic PK and LDH activities, whereas plasma tPRL177, tPRL188, glycine and lysine concentrations were significantly lower than in fish retained in fresh water. There was a significant interaction between nutritional state and salinity that affected the tPRL188:tPRL177 ratio and plasma concentrations of Cl-, GH, glucose, aspartate, tyrosine, serine, alanine, glycine, arginine and hepatic PK, LDH, AlaAT, aspartate aminotransferase, glutamate dehydrogenase and HOAD activities. These results, taken together, indicate that food-deprived fish did not regulate their plasma Cl- levels, despite an enhancement of plasma hormonal and metabolic responses in sea water. Our study also suggests the possibility that plasma prolactin and essential amino acids may be playing an important role in the seawater acclimation process in tilapia.
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PMID:Food-deprivation affects seawater acclimation in tilapia: hormonal and metabolic changes 932 Mar 94

We studied the effects of TRH on the cytosolic free calcium concentration ([Ca2+]i) of female rat pituitary prolactin-secreting (lactotroph) and GH-secreting (somatotroph) cells in the early postnatal period, i.e. at postnatal days 5 and 10. [Ca2+]i of single identified lactotrophs and somatotrophs was recorded by dual-emission microspectrofluorimetry using the intracellular fluorescent calcium probe indo 1. An application of TRH (100 nM, 10 s) induced a marked [Ca2+]i increase in 65% of neonatal lactotrophs and 34% of neonatal somatotrophs while the remaining cells were unaffected. Most of the responsive cells, both lactotrophs and somatotrophs, exhibited a similar biphasic Ca2+ response, made up of an initial rapid large increase in [Ca2+]i followed by sustained [Ca2+]i fluctuations. In both cell types, removal of Ca2+ from the extracellular medium or addition of the Ca2+ channel blocker, cadmium chloride (500 microM), inhibited the second phase whereas the first phase persisted. Furthermore, in both cell types, protein kinase C (PKC) depletion by incubation in phorbol myristate acetate (1 microM) for 24 h abolished the second phase but did not inhibit the first phase. Conversely, when cells were pretreated with the Ca(2+)-ATPase inhibitor, thapsigargin (100 nM), all TRH-induced [Ca2+]i changes in both cell types disappeared. TRH therefore induces a biphasic increase in [Ca2+]i involving intra- and extracellular Ca2+ in neonatal lactotrophs and somatotrophs as it does in adult lactotrophs. The first phase is presumably due to mobilization of Ca2+ from intracellular stores whereas the second phase presumably results from a PKC-sensitive influx of Ca2+. TRH action on membrane potential was then investigated using the patch-clamp technique in the whole-cell mode. TRH-induced changes in membrane potential consisted of an initial hyperpolarization followed by depolarization and action potential firing. We also investigated TRH action on prolactin and GH secretion by neonatal pituitary cells using RIA. Surprisingly, static assays of prolactin and GH revealed only stimulation of prolactin release by TRH but no effect on GH secretion, although, as expected, GH-releasing factor was a potent agonist of GH secretion. Our results suggest that TRH regulates neonatal lactotrophs and somatotrophs differently, in that the [Ca2+]i changes do not correlate with stimulation of exocytosis in the latter cell type.
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PMID:Intracellular calcium concentration and hormone secretion are controlled differently by TRH in rat neonatal lactotrophs and somatotrophs. 937 26

Previously, we have shown that prolactin inhibits epidermal growth factor (EGF)-induced mitogenesis in mouse mammary epithelial cells without altering the response to other growth promoting agents. This effect has been associated with reduced EGF-induced EGF receptor (EGFR) tyrosine phosphorylation, Grb-2 association, and Ras activation. Our current hypothesis is that prolactin induces an alteration in EGFR kinase activity via a phosphorylation-dependent mechanism. To test this hypothesis, we treated normal murine mammary gland cells with or without 100 ng/ml prolactin. EGFR isolated by wheat germ agglutinin affinity chromatography from nontreated cells exhibited substantial ligand-induced phosphorylation, and EGFR isolated from prolactin-treated cells displayed minimal EGF-induced EGFR phosphorylation, as well as decreased kinase activity toward exogenous substrates. The observed decrease in ligand-induced EGFR phosphorylation could not be attributed to either differential amounts of EGFR, decreased EGF binding affinity, or the presence of a phosphotyrosine phosphatase or ATPase. EGFR isolated from prolactin-treated cells exhibited increased phosphorylation on threonine. Removal of this phosphorylation with alkaline phosphatase restored EGFR kinase activity to levels observed in nontreated cells. Therefore, these results suggest that prolactin antagonizes EGF signaling by increasing EGFR threonine phosphorylation and decreasing EGF-induced EGFR tyrosine phosphorylation.
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PMID:Prolactin decreases epidermal growth factor receptor kinase activity via a phosphorylation-dependent mechanism. 942 87


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