Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: DrugBank:EXPT00514 (Amiloride)
 1,513 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Endothelin, a 21-amino acid vasoactive peptide, is among the most potent positively inotropic agents yet described in mammalian heart. Having demonstrated that endothelin's inotropic effect is due, in part, to an apparent sensitization of cardiac myofilaments to intracellular calcium, we determined whether this could be due to a rise in intracellular pH (pHi). In isolated adult rat ventricular cells loaded with the H(+)-selective fluorescent probe BCECF, 100 pM endothelin increased contractile amplitude to 190 +/- 26% of baseline and pHi by 0.08 +/- 0.02 (n = 8), whereas 1 nM endothelin increased pHi by 0.13 +/- 0.03 with little further increase in contractility. Amiloride (10(-4)M) prevented the increase in pHi in response to endothelin and reduced the inotropic response by 45%, although the inotropic effect could be readily restored by subsequent NH4Cl-induced alkalinization. Similarly, inhibitors of protein kinase C (H-7 and sphingosine) diminished or abolished the rise in pHi after endothelin superfusion while causing a decline in its inotropic effect comparable with that observed with amiloride. Pretreatment with pertussis toxin, which we have demonstrated results in complete ADP-ribosylation of the alpha-subunits of Go and Gi GTP-binding proteins and abolition of endothelin's positive inotropic effect, only partially reduced the intracellular alkalinization induced by the peptide, suggesting a complex signal transduction mechanism. Thus, the positive inotropic action of endothelin is due in part to stimulation of the sarcolemmal Na(+)-H+ exchanger by a protein kinase C-mediated pathway, resulting in a rise in pHi and sensitization of cardiac myofilaments to intracellular Ca2+.
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PMID:Endothelin and increased contractility in adult rat ventricular myocytes. Role of intracellular alkalosis induced by activation of the protein kinase C-dependent Na(+)-H+ exchanger. 184 55

In the present investigation, sodium fluoride (NaF) was employed to explore the role of guanine nucleotide-binding proteins (G-proteins), protein kinase-C, or cytosolic calcium [( Ca]i) in the regulation of cytosolic pH [( pH]i) in dispersed bovine parathyroid cells, using the pH-sensitive fluorescent dye BCECF. When cells acidified by nigericin in Na-free medium were resuspended in Na-containing buffer, [pH]i returned to basal levels. This recovery was blocked by continued removal of Na+ or the addition of amiloride. NaF (10 mM) increased [32P]phosphate incorporation into phosphatidylinositol bisphosphate, suggesting an increase in phosphatidylinositol bisphosphate turnover. NaF caused an initial acidification, followed by an alkaline recovery in a dose-dependent manner (1-10 mM). Amiloride blocked the NaF-induced alkaline recovery. The protein kinase-C activator phorbol 12-myristate 13-acetate (10(-7) M) caused cytosolic alkalinization, while the protein kinase-C inhibitor H7 (6 x 10(-5) M) significantly inhibited the NaF-induced alkaline recovery. Pertussis toxin (1 microgram/ml) did not affect the NaF-induced changes in [pH]i. Removal of extracellular Ca2+ with EGTA blocked the NaF-induced increase in [Ca]i and alkaline recovery. Ionomycin (5 x 10(-7) M) caused cytosolic alkalinization, but pretreatment with EGTA inhibited the ionomycin-induced cytosolic alkalinization. The present studies clearly demonstrated the presence of an amiloride-sensitive Na+/H+ exchanger in parathyroid cells. Our findings suggest that the NaF-induced cytosolic alkaline recovery was via two complementing pathways: 1) activation of protein kinase-C, followed by stimulation of a Na+/H+ exchanger, and 2) existence of extracellular calcium and/or an increase in [Ca]i.
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PMID:Regulation of cytosolic pH in bovine parathyroid cells: effect of fluoride. 253 2

The effect of amiloride on the hormonal regulation of adenylate cyclase was studied in the rat anterior pituitary. The diuretic did not alter basal adenylate cyclase but augmented the enzyme activity in an irreversible manner in the presence of guanosine 5'-O-(thiotriphosphate) (GTP gamma S) stimulated adenylate cyclase at lower concentrations and inhibited at higher concentrations. Amiloride treatment enhanced the stimulatory and abolished the inhibitory phase of GTP gamma S action. In addition, amiloride also attenuated the inhibitory effects of atrial natriuretic factor (ANF 99-126) and angiotensin II on cAMP levels and adenylate cyclase activity. On the other hand, amiloride showed an additive effect on the stimulation exerted by corticotropin-releasing factor and vasoactive intestinal peptide on adenylate cyclase in anterior pituitary and on isoproterenol-stimulated cAMP levels in cultured vascular smooth muscle cells. Pertussis toxin, in the presence of [alpha-32 P]NAD, catalyzed the ADP-ribosylation of two protein bands of Mr 41,000 and 39,000, referred to as Gi and Go, respectively, in the anterior pituitary, and 40,000-Da protein in the aorta, referred to as Gi. Amiloride treatment inhibited the labeling of all these bands in a concentration- and time-dependent manner. Similarly, the pertussis toxin-catalyzed ADP-ribosylation of purified Gi from bovine brain was also inhibited by amiloride treatment. However, amiloride had no significant effect on the cholera toxin-catalyzed ADP-ribosylation of Gs. These data suggest that amiloride interacts with the guanine nucleotide regulatory proteins Gi and Go. Modification of Gi results in the attenuation of hormone-induced adenylate cyclase and cAMP inhibition. However, the interaction between amiloride and Go and the consequent Ca2+ mobilization and phosphatidylinositol turnover have to be investigated.
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PMID:Amiloride interacts with guanine nucleotide regulatory proteins and attenuates the hormonal inhibition of adenylate cyclase. 254 11

alpha 2-Adrenoceptor agonists inhibit glucose-stimulated insulin release and glucose utilization in pancreatic islets. In isolated pancreatic islets of the rat, the Ca2+ channel agonists CGP-28392 and BAY-K-8644 increased insulin release in the presence of clonidine. Neither CGP-28392 nor BAY-K-8644 antagonized the effect of clonidine on glucose utilization. The Ca2+ ionophore, ionomycin, also did not affect glucose utilization in the presence or absence of clonidine. Glucagon partly reversed the effects of clonidine on insulin release, and it potentiated glucose-stimulated insulin release in the absence of clonidine. Glucagon reversed the effects of clonidine on glucose utilization. Amiloride antagonized the effects of clonidine on insulin secretion but did not enhance markedly glucose utilization in the presence or absence of clonidine. Carbamylcholine and arecoline reversed the effects of clonidine on glucose utilization and partly reversed the effects on insulin release in the absence of extracellular Ca2+. Prostaglandin (PG) E2, but not PGF2 alpha, inhibited glucose utilization in a time- and concentration-dependent manner. PGE2 also inhibited glucose-stimulated insulin release. Pertussis toxin blocked both actions of PGE2. The cyclooxygenase inhibitor indomethacin did not affect insulin release or glucose utilization in the presence of clonidine. Thus, elevated intracellular Ca2+ levels antagonize the effects of clonidine on insulin release, whereas other mediators appear to be required to alter glucose utilization.
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PMID:Calcium mobilization, prostaglandin E2 and alpha 2-adrenoceptor modulation of glucose utilization and insulin secretion in pancreatic islets. 254 83

The natriuretic effects of atrial peptide hormones have been attributed, at least in part, to their stimulation of guanylate cyclase activity in renal cell membranes. The effects of atrial natriuretic factor (ANF) on stimulation of cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) accumulation were investigated in cloned human kidney tumor (hKT) cells and parent cells from a human renal tumor epithelial cell line (SK-NEP-1). Human ANF-(99-126) (10(-6)M) stimulated (p less than 0.001) cellular cGMP accumulation in a dose-dependent manner from a basal level of 0.26 +/- 0.04 to 3.73 +/- 0.81 pmol/mg protein/5 mi (mean +/- SEM, n = 13). ANF stimulation of cGMP accumulation was specific, in that high concentrations (10(-6)M) of atriopeptin I [rat ANF-(103-123)], angiotensin II, arginine vasopressin, and amiloride (10(-4)M) did not increase basal cGMP. Amiloride (10(-4)M) enhanced (p less than 0.01, n = 6) the ANF stimulation of cGMP accumulation (1.24 +/- 0.39 pmol/mg protein/5 min), particularly at low doses of ANF (10(-10)M) where stimulation by ANF without amiloride (0.34 +/- 0.08 pmol/mg protein/5 min) was barely distinguishable from a basal level (0.19 +/- 0.02 pmol/mg protein/5 min) of cGMP accumulation. The stimulatory effect of ANF (1.59 +/- 0.07 pmol/mg protein/5 min) was attenuated (0.75 +/- 0.06 pmol/mg protein/5 min, p less than 0.01, n = 6) by preincubation of the cells with pertussis toxin but not by cholera toxin. ANF (4.56 +/- 0.93 pmol/mg protein/5 min, n = 8) did not affect cAMP accumulation (4.32 +/- 0.98 pmol/mg protein/5 min) in hKT cells. This is the first report of an ANF responsive human renal cell line, and its use should facilitate investigation of ANF-receptor interactions.
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PMID:Atrial natriuretic factor effects on cyclic nucleotides in a human renal cell line. 256 5

In this present study, the effects of ET-1 on intracellular free calcium concentration ([Ca2+]i) and the underlying mechanisms were investigated in cultured neonatal rat myocardial cells loaded with fura-2/AM. The results are as follows. ET-1 induced an increase of [Ca2+]i in a dose-dependent manner, which consisted of a transient and sustained phase. BQ123, a selective ETA receptor antagonist, blocked the ET-1 induced [Ca2+]i responses, suggesting that these responses were mediated by ETA receptors. After removal of extracellular Ca2+, ET-1 induced the transient increase of [Ca2+]i without the sustained change. Protein kinase C (PKC) agonist PMA attenuated the ET-1 induced transient [Ca2+]i increase. Amiloride and nifedipine did not block the [Ca2+]i change induced by ET-1. After pretreatment of myocardial cells with pertussis toxin, ET-1 also induced the transient increase of [Ca2+]i but did not affect the sustained increase. These results suggest that the transient [Ca2+]i increase may involve pertussis toxin-insensitive G protein and the sustained one may be caused by extracellular calcium influx, in which pertussis toxin sensitive G protein is involved. Furthermore, PKC, but not Na+/H+ exchange, plays an important role in these effects.
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PMID:[Effect of ET-1 on intracellular free calcium in cultured neonatal myocardial cells]. 1149 66