Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recordings of fura-2 fluorescence from single osteoblastic MC3T3-E1 cells showed that bradykinin (BK, 1 microM) induced a rapid increase in cytoplasmic free Ca2+ (Cai2+, from 114 +/- 13 to 239 +/- 17 nM, mean +/- SEM). Following this initial transient (less than 1 minute) increase there was a second slow increase in Cai2+ (from 117 +/- 11 to 151 +/- 12 nM). Incubation in buffer with no Ca2+ did not affect the first rapid BK-induced increase in Cai2+ but eliminated the second slow increase. Addition of indomethacin or hydrocortisone to the incubation buffer did not inhibit the effect of BK on Cai2+. BK caused a dose-dependent initial rapid increase in Cai2+ with threshold at 1 nM and a maximal effect (241 +/- 30% of basal Cai2+ concentration) at 0.1 microM. The B1 BK receptor agonist des-Arg9-BK (1 microM) caused only a small increase in Cai2+ in MC3T3-E1 cells (from 101 +/- 20 to 140 +/- 4 nM). BK dose and time dependently stimulated the formation of inositol phosphates in MC3T3-E1 cells with EC50 at 2.4 nM and a significant increase in inositol trisphosphate already seen after 15 s. The Ca2+ ionophore ionomycin induced a rapid increase in Cai2+ and prostaglandin E2 (PGE2) formation in MC3T3-E1 cells. Forskolin (10-30 microM) increased cyclic AMP accumulation but did not affect Cai2+ or PGE2 formation. Depletion of extracellular Ca2+ significantly reduced (but did not abolish) BK-induced PGE2 formation. The initial action of BK on Cai2+ is probably due to an inositol-(1,4,5)-trisphosphate-mediated rapid release of Ca2+ from intracellular stores in osteoblasts and is followed by an influx of extracellular Ca2+. The effect is due to B2 BK receptor occupancy and is not secondary to the prostaglandin synthesis. The BK-induced breakdown of phosphatidylinositol-(4,5)-bisphosphate with a subsequent increase in Cai2+ may be involved in BK-induced prostaglandin formation in osteoblasts.
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PMID:Bradykinin induces formation of inositol phosphates and causes an increase in cytoplasmic Ca2+ in the osteoblastic cell line MC3T3-E1. 164 60

In the present studies the chronic effects of glucocorticoids and drugs activating cAMP-dependent pathways on the production and secretion of immunoreactive (ir) ANP from long term monolayer cultures of neonatal rat hypothalamic neurons were examined. Forskolin treatment increased ir-ANP release in a time-dependent and dose-related manner, with an EC50 of approximately 30 microM; at a lower dose of 10 microM, forskolin doubled ir-ANP release (P less than 0.01) compared to that in control cultures (mean +/- SEM, 9.6 +/- 0.3 pg/well; n = 4). While dexamethasone (DM) alone did not affect basal secretion of ir-ANP, 10 nM of the glucocorticoid significantly enhanced the effect of forskolin (10 microM) by raising ir-ANP release approximately 3 times that induced by forskolin alone (P less than 0.001). This potentiation of DM was both time dependent and dose responsive, with an EC50 of 1 nM; this effect was significantly suppressed by 100 nM RU38486, a glucocorticoid or type II receptor antagonist, but not by RU28318, a mineralocorticoid receptor antagonist. In addition, forskolin (10 microM) or DM (10 nM) alone significantly increased ir-ANP production approximately 1.4 times (P less than 0.05) and 1.3 times (P less than 0.05) over that of control cultures, respectively, whereas concurrent treatment with forskolin and DM increased ir-ANP production by approximately 1.8 times (P less than 0.01). These changes were reflected by a corresponding increment in the abundance of pro-ANP mRNA in the cultures, as demonstrated by Northern blot analysis. We conclude from the present findings that glucocorticoid- and cAMP-dependent pathways may modulate the function of ANP neurons in rat hypothalami by regulating the secretion and production of the neuropeptide at the genomic level.
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PMID:Forskolin-induced immunoreactive atrial natriuretic peptide (ANP) secretion and pro-ANP messenger ribonucleic acid expression of hypothalamic neurons in culture: modulation by glucocorticoids. 182 78

We studied the effects of adenosine and adenosine derivatives on adenylate cyclase activity in cultured endothelial cells from bovine pulmonary artery. Basal and stimulated enzyme activities were measured in membrane preparations using [alpha-32P]ATP as the substrate and chromatographic isolation of formed [32P]cAMP. Basal cyclase activity was 11 +/- 1 (mean +/- SEM) pmol/mg protein/min. Forskolin, 5'-guanylylimidodiphosphate (Gpp(NH)p) and (-)isoproterenol stimulated adenylate cyclase in a concentration-dependent manner, producing maximal stimulations of three, seven and four times the basal activity respectively. In the presence of adenosine deaminase, cyclohexyladenosine, an A1 agonist, had no effect on basal and forskolin- or Gpp(NH)p-stimulated activities, whereas 5'-(N-ethyl)-carboxamidoadenosine (NECA), an A2 agonist, had a small stimulatory effect (52% increase over basal). In the presence of IBMX, adenosine and two P-site agonists, 2',5'-dideoxyadenosine (DDA) and 2'-deoxyadenosine-3'-monophosphate (2'-deoxy-3'-AMP), inhibited forskolin (30 microM)-stimulated adenylate cyclase activity with an order of potency of 2'-deoxy-3'-AMP greater than DDA greater than adenosine. DDA and 2'-deoxy-3'-AMP were also able to inhibit cyclase activity stimulated by Gpp(NH)p (10(-5)M) or isoproterenol (10(-6)M) with the same order of potency. Only 2'-deoxy-3'-AMP inhibited the stimulated adenylate cyclase activity by more than 50% (IC50 = 19-32 microM). These findings indicate that (1) long-term cultured endothelial cells from bovine pulmonary artery express A2 and beta-adrenergic receptors which stimulate adenylate cyclase activity through Gs transducer proteins, and (2) the natural compound and P-site agonist, 2'-deoxy-3'-AMP, is a potent inhibitor, and possibly a natural regulator, of adenylate cyclase activity in this tissue.
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PMID:Modulation of adenylate cyclase activity in cultured bovine pulmonary arterial endothelial cells. Effects of adenosine and derivatives. 246 5

We have examined the placental vascular responses to forskolin in 8 near-term sheep. The drug was administered for 5 min at 1 ml/min of 10(-3) M forskolin via a retrograde uterine arterial catheter. Blood flows were measured with radioactive microspheres. Forskolin increased the nonplacental uterine blood flow from 0.318 +/- 0.031 (SEM) to 0.738 +/- 0.071 ml/min per g of tissue, P less than 0.001. The nonplacental uterine vascular resistance decreased from 308 +/- 26 to 132 +/- 12 mmHg/ml/min per g, P less than 0.001. Forskolin increased the placental blood flow from 1.8 +/- 0.18 to 2.08 +/- 0.16 ml/min per g of tissue, P less than 0.05. The placental vascular resistance decreased from 54.7 +/- 5.1 to 45.9 +/- 3.7 mmHg/ml/min per g, P less than 0.03. In the same animals we then infused angiotensin II at 5 micrograms/min via the jugular vein to induce placental vasoconstriction. In this series, the forskolin increased the nonplacental uterine blood flow from 0.141 +/- 0.016 to 0.485 +/- 0.079 ml/min per g of tissue, P less than 0.001, and the uterine vascular resistance decreased from 968 +/- 104 to 283 +/- 36 mmHg/ml/min per g, P less than 0.001. The placental blood flow increased from 2.08 +/- 0.012 to 2.69 +/- 0.17 ml/min per g of tissue, P less than 0.01 and placental vascular resistance decreased from 61.9 +/- 4.4 to 46.0 +/- 3.7 mmHg/ml/min per g, P less than 0.001.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Forskolin dilates the maternal ovine placental vascular bed. 306 39

Forskolin is a direct stimulant of adenylate cyclase and increases cAMP production. It also acts as a vasodilator. To study the effect of forskolin infusion on rabbit maternal vascular resistance, we instrumented 11 pregnant rabbits with catheters in the left ventricle, jugular vein, and left and right femoral arteries. After a 2-day recovery period, one of two protocols was performed. In the control period of the first protocol (N = 6), 50% ethanol in saline was infused at 0.103 ml.min-1 for 5-min. Forskolin (10(-3) M) in 50% ethanol was then infused for 5 min at 0.103 ml.min-1. After each infusion period, regional blood flows were measured by microsphere injection. Data are expressed as means +/- SEM. Blood pressure decreased from 81 +/- 3 to 79 +/- 3 mm Hg, (P less than 0.05, N = 10) during forskolin infusion. Total placental resistance fell from 180.3 +/- 10.7 to 133.8 +/- 12.0 mm Hg.min.ml-1 per gram, P less than 0.05. Cerebral, coronary, and renal vascular resistance fell significantly. During the second protocol (N = 5), angiotensin II (0.05 microgram.min-1) was infused for 5 min followed by the addition of forskolin (10(-3) M at 0.103 ml.min-1) to the infusate. Regional blood flows, vascular resistances and blood pressures were determined. Blood pressure fell from 99 +/- 6 to 92 +/- 7 mm Hg (P less than 0.05) when forskolin was added to the infusate. Placental resistance fell from 202.5 +/- 21.6 to 158.0 +/- 29.0 mm Hg.min.ml-1 per gram (P less than 0.05). While cerebral vascular resistance did not change, renal and coronary resistances fell in response to forskolin. This study demonstrates that forskolin is able to dilate rabbit placental vessels alone and in the presence of the vasoconstrictive agent angiotensin II.
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PMID:Effects of forskolin on placental vascular resistance in rabbits. 342 Jan 8

The cystic fibrosis transmembrane conductance regulator (CFTR) is an epithelial Cl- channel regulated by protein kinase A. The most common mutation in cystic fibrosis (CF), deletion of Phe-508 (delta F508-CFTR), reduces Cl- secretion, but the fatal consequences of CF have been difficult to rationalize solely in terms of this defect. The aim of this study was to determine the role of CFTR in HCO3- transport across cell membranes. HCO3- permeability was assessed from measurements of intracellular pH [pHi; from spectrofluorimetry of the pH-sensitive dye 2',7'-bis(2-carboxyethyl)-5-(and -6)carboxyfluorescein] and of channel activity (patch clamp; cell attached and isolated, inside-out patches) on NIH 3T3 fibroblasts and C127 mammary epithelial cells transfected with wild-type CFTR (WT-CFTR) or delta F508-CFTR, and also on mock-transfected cells. When WT-CFTR-transfected cells were acidified (pulsed with NH4Cl) and incubated in Na(+)-free (N-methyl-D-glucamine substitution) solutions (to block Na(+)-dependent pHi regulatory mechanisms), pHi remained acidic (pH approximately 6.5) until the cells were treated with 20 microM forskolin (increases cellular [cAMP]); pHi then increased toward (but not completely to) control level (pHi 7.2) at a rate of 0.055 pH unit/min. Forskolin had no effect on rate of pHi recovery in delta F508 and mock-transfected cells. This Na(+)-independent, forskolin-dependent pHi recovery was not observed in HCO3-/CO2-free medium. Forskolin-treated WT-CFTR-transfected (but not delta F508-CFTR or mock-transfected) cells in Cl(-)-containing, HCO3(-)-free solutions showed Cl- channels with a linear I/V relationship and a conductance of 10.4 +/- 0.5 pS in symmetrical 150 mM Cl-. When channels were incubated with different [Cl-] and [HCO3-] on the inside and outside, the Cl-/HCO3- permeability ratio (determined from reversal potentials of I/V curves) was 3.8 +/- 1.0 (mean +/- SEM; n = 9); the ratio of conductances was 3.9 +/- 0.5 (at 150 mM Cl- and 127 mM HCO3-. We conclude that in acidified cells the WT-CFTR functions as a base loader by allowing a cAMP-dependent influx of HCO3- through channels that conduct HCO3- about one-quarter as efficiently as it conducts Cl-. Under physiological conditions, the electrochemical gradients for both Cl- and HCO3- are directed outward, so CFTR likely contributes to the epithelial secretion of both ions. HCO3- secretion may be important for controlling pH of the luminal, but probably not the cytoplasmic, fluid in CFTR-containing epithelia. In CF, a decreased secretion of HCO3- may lead to decreased pH of the luminal fluid.
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PMID:Bicarbonate conductance and pH regulatory capability of cystic fibrosis transmembrane conductance regulator. 751 98

The effects of beta-adrenergic agonists on pHi were studied on single ventricular myocytes isolated from adult rat heart and loaded with the acetoxymethyl ester (AM) form of the pH indicator SNARF-1. In modified Krebs' solution containing 20 mmol/L HEPES and 4.4 mmol/L HCO3-, isoproterenol (1 mumol/L) caused a significant decrease of steady-state pHi from 7.20 +/- 0.02 to 7.13 +/- 0.02 (mean +/- SEM) within 2 minutes. This acidification, which was also observed in myocytes that were preloaded with the Ca2+ chelator BAPTA and superfused with nominally Ca(2+)-free solution, was blocked by propranolol as well as by the specific beta 1-antagonist CGP 20712 A but not by the beta 2-antagonist ICI 118,551. Forskolin (10 mumol/L) induced a similar reversible decrease of pHi (average decrease, 0.11 +/- 0.02 pH unit). Furthermore, adenosine (100 mumol/L) substantially attenuated the isoproterenol-induced decrease of pHi. The effect of isoproterenol was not prevented by inhibitors of the Na(+)-H+ antiport, amiloride (1 mmol/L) and 2-N,N-hexamethylene amiloride (20 mumol/L). On the other hand, blockers of Cl- transport mechanisms, DIDS (200 mumol/L) and probenecid (100 mumol/L), inhibited this acidification, Isoproterenol also failed to induce a decrease of steady-state pHi in myocytes incubated in Cl(-)-free medium. Rather, the initial rate of rise of pHi observed on removal of external Cl- ions was significantly increased in the presence of isoproterenol or dibutyryl cAMP. Because the alkalinization induced by removal of Cl- ions is mainly due to reversal of the Cl(-)-HCO3- exchanger, the augmentation of this initial rate of pHi rise directly points to a beta-adrenergic stimulation of the exchanger. Furthermore, the pHi recovery following NH4Cl exposure was accelerated by isoproterenol in the presence of probenecid, indicating that the Na(+)-HCO3- cotransport and/or the Na(+)-H+ antiport also could be activated.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Chloride dependence of pH modulation by beta-adrenergic agonist in rat cardiomyocytes. 792 32

The purpose of this study is to characterize the adenyl cyclase (AC) activity in Fisher rat thyroid cell line when stimulated with several agonists, such as: forskolin, sodium fluoride, Gpp(NH)p (guanosine-5'-(beta, gamma -imino) triphosphate or thyrotropin. The following studies such as: dose-response, pH, temperature, time-response, millieu concentration, 3H-thymidine uptake, Km and Vm study were also performed. Adenyl cyclase activity was measured as adenosine 3', 5'-cyclic monophosphate generated by cell cultures in 120- minutes incubation at 37 degrees C. The basal AC activity was 15.0 +/- 7.0 (mean +/- SEM, n = 6) pmol/100,000 cells/120 minutes. Forskolin at 0.1 mM increased the AC activity to 10 folds of basal AC activity. Thyroid stimulating hormone at 1 mU/ml and 10 mU/ml increased the AC activity 2 and 15 folds, respectively. Sodium fluoride stimulation study demonstrated dual actions of fluoride on adenylate cyclase; when the cells were assayed with increasing concentration of NaF, the AC activity increased as the concentration of NaF increased from 0.01 to 1 mM, but decreased strikingly as that concentration increased from 1 mM to 100 mM. When the concentration of nonhydrolyzable guanine nucleotide analogs increased in the presence of TSH, there was first an increase in adenylate cyclase activity, followed by a decrease at higher concentration. The amount of cAMP generation was much higher (P < 0.05) in hypotonic than in isotonic millieu. When the incubation temperature raised to 56 degrees C, all the AC activity was diminished. The optimal pH for AC activity was in the range of 7.4 and 8.0.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The characterization of adenyl cyclase activity in FRTL-5 cell line. 838 68

Repeated stimulation of pituitary cell cultures with GH-releasing hormone (GHRH) results in diminished responsiveness, a phenomenon referred to as homologous desensitization. One component of GHRH-induced desensitization is a reduction in GHRH-binding sites, which is reflected by the decreased ability of GHRH to stimulate a rise in intracellular cAMP. In the present study, we sought to determine if homologous down-regulation of GHRH receptor number is due to a decrease in GHRH receptor synthesis. To this end, we developed and validated a quantitative RT-PCR assay system that was capable of assessing differences in GHRH-R messenger RNA (mRNA) levels in total RNA samples obtained from rat pituitary cell cultures. Treatment of pituitary cells with GHRH, for as little as 4 h, resulted in a dose-dependent decrease in GHRH-R mRNA levels. The maximum effect was observed with 0.1 and 1 nM GHRH, which reduced GHRH-R mRNA levels to 49 +/- 4% (mean +/- SEM) and 54 +/- 11% of control values, respectively (n = three separate experiments; P < 0.05). Accompanying the decline in GHRH-R mRNA levels was a rise in GH release; reaching 320 +/- 31% of control values (P < 0.01). Because of the possibility that the rise in medium GH level is the primary regulator of GHRH-R mRNA, we pretreated pituitary cultures for 4 h with GH to achieve a concentration comparable with that induced by a maximal stimulation with GHRH (8 micrograms GH/ml medium). Following pretreatment, cultures were stimulated for 15 min with GHRH and intracellular cAMP accumulation was measured by RIA. GH pretreatment did not impair the ability of GHRH to induce a rise in cAMP concentrations. However, as anticipated, GHRH pretreatment (10 nM) significantly reduced subsequent GHRH-stimulated cAMP to 46% of untreated controls. These data suggest that GHRH, but not GH, directly reduces GHRH-R mRNA levels. To determine whether this effect was mediated through cAMP, cultures were treated with forskolin, a direct stimulator of adenylate cyclase. Forskolin (10 microM) significantly reduced GHRH-R mRNA concentrations (37 +/- 6% of control values) indicating that GHRH acts through the cAMP-second messenger system cascade to regulate GHRH-R mRNA. The somatostatin analogue, octreotide (10 nM), which has been previously reported to decrease adenylate cyclase activity, did not affect GHRH-R mRNA levels. Taken together, these results indicate that GHRH inhibits the production of its own receptor by a receptor-mediated, cAMP-dependent reduction of GHRH-R mRNA accumulation.
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PMID:Homologous down-regulation of growth hormone-releasing hormone receptor messenger ribonucleic acid levels. 904 9