Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.6.1.1 (adenylate cyclase)
 19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The mechanism by which neuropeptide Y (NPY) potentiates the vasoconstriction induced by alpha 1-adrenoceptor agonists was investigated in 3rd generation mesenteric arterioles of the rat. 2. At a maximally active concentration, nitrendipine (10(-6) M) displaced to the right the concentration-response curves to noradrenaline (pD2 decreased from 6.2 +/- 0.06 to 5.7 +/- 0.03) and phenylephrine (pD2 decreased from 5.6 +/- 0.03 to 5.3 +/- 0.03). Diltiazem (10(-5) M) also shifted to the right the concentration-response curve to phenylephrine (pD2 decreased from 6.0 +/- 0.06 to 5.5 +/- 0.04). In addition, the maximal response to phenylephrine was significantly decreased in the presence of either nitrendipine or diltiazem. 3. In the absence of a calcium channel blocking agent, NPY (100 nM) produced a leftward shift of the concentration-response curves to noradrenaline (pD2 increased from 6.2 +/- 0.06 to 6.5 +/- 0.05) and phenylephrine (pD2 increased from 5.6 +/- 0.03 to 6.0 +/- 0.06 and from 6.0 +/- 0.06 to 6.3 +/- 0.11). In the presence of either nitrendipine (10(-6) M) or diltiazem (10(-5) M), NPY (100 nM) did not alter the concentration-response curves to either noradrenaline or phenylephrine. 4. NPY was added to arterioles brought to the same level of tension (40% of the maximal contraction) either by phenylephrine alone (1.5 x 10(-6) M) or by a higher concentration of phenylephrine (3 x 10(-6) M) followed by the addition of prazosin (1.3 x 10(-9) M; a concentration at which it partially blocks alpha 1-adrenoceptors). In these conditions, the response to phenylephrine was completely abolished by nitrendipine (10-6 M) or by diltiazem (10-5M). Furthermore, NPY (10-1" to 10-7M) increased the arteriolar tension up to the maximal contractile capacity of the vessels with pD2 values of 8.6 + 0.02 and 8.7 + 0.01, in the absence and presence of prazosin, respectively. 5. Prazosin was replaced in the above protocol by other vasodilator agents acting through different mechanisms. Whether in the presence of 2 x 10-7M forskolin, 6 x 10-7M sodium nitroprusside (which stimulate adenylate cyclase or guanylate cyclase, respectively) or 2 x 10- 7M diltiazem (a concentration at which calcium entry is partially blocked), NPY enhanced phenylephrine-induced contraction to the maximum level with an identical potency (pD2 values of the peptide ranged from 8.3 to 8.7). 6. The results show that, in rat mesenteric arterioles, NPY potentiates only the calcium entry blockersensitive component of contraction induced by stimulation of alpha,-adrenoceptors. In addition, they provide evidence that the peptide counteracts with an equal potency the inhibitory effect of partial block of alpha,-adrenoceptors and of relaxing agents acting through different mechanisms. It is suggested that NPY enhances calcium entry induced by stimulation of alpha l-adrenoceptors in this tissue.
 ...
PMID:Enhancement by neuropeptide Y (NPY) of the dihydropyridine-sensitive component of the response to alpha 1-adrenoceptor stimulation in rat isolated mesenteric arterioles. 197 Feb 70

Proximal tubules were isolated from the rat kidney by collagenase digestion of the cortical tissue followed by Percoll gradient centrifugation. Microscopic and hormone-stimulated adenylate cyclase activity studies proved the purity of the preparation. [3H]Prazosin, [3H]rauwolscine, and [125I]iodocyanopindolol were used to identify and quantitate respectively the alpha 1-, alpha 2- and beta-adrenergic receptors. Proximal tubular (F4) particulate fraction was compared against other cortical nephron segment (F1, F2) fractions and the total collagenase-digested cortex particulate suspension (Ft). Proximal tubules were enriched in alpha 1- and alpha 2-adrenergic receptors compared with Ft (alpha 1-receptor, 100.4 +/- 4.5 vs. 87.4 +/- 4.9; alpha 2-receptor, 250 +/- 16.2 vs. 185.1 +/- 12 fmol/mg protein). The fractions enriched in glomeruli and distal tubular segments (F1, F2) had relatively low concentrations of alpha 1- and alpha 2-adrenergic receptors. In contrast, beta-adrenergic receptor concentration in the proximal tubules was approximately 25% of that in the Ft fraction and approximately 10% of that in the F1 fraction. Isoproterenol-stimulated adenylate cyclase activities in the different fractions corroborated well with the pattern suggested by the [125I]iodocyanopindolol binding studies. Our results suggest that whole-cortex preparation radioligand binding studies may reflect proximal tubular alpha 1- and alpha 2-adrenergic receptor changes quite well. They may, however, miss or give erroneous impressions about beta-adrenergic receptor changes occurring in different cortical nephron segments.
 ...
PMID:Alpha- and beta-adrenergic receptors in proximal tubules of rat kidney. 282 36

Halothane, in anesthetic concentrations (0.6-1.8 volumes/100 ml), produced a dose-dependent decrease in myocardial cyclic AMP (cAMP) content and an increase in cyclic GMP (cGMP) content in mice exposed to a continuous flow of the anesthetic carried in air for 15 min. Atropine (up to 20 mg/kg i.p.) did not alter significantly the myocardial cyclic nucleotides content or the effect of halothane on cAMP and cGMP content. Prazosin and yohimbine had no significant effect on cAMP or cGMP content in the absence of halothane. Both alpha adrenergic antagonists inhibited the halothane-induced increase in cGMP content (ID50, 0.24 and 0.54 mumol/kg i.p. for prazosin and yohimbine, respectively). In contrast, the decrease in cAMP content induced by halothane was not altered by alpha adrenergic antagonists. Propranolol (2 mg/kg i.p.) diminished myocardial cAMP level and prevented the halothane effect on myocardial cAMP content. Pretreatment with 6-hydroxydopamine did not change the cGMP response to halothane. Thus, the action of halothane on myocardial cyclic nucleotides content appears to be predominantly a peripheral effect, not related to cellular mechanisms mediated by muscarinic receptors. The results suggest that the increase in cGMP content induced by halothane does not require intact adrenergic nerve endings and that cellular processes associated with the alpha adrenoceptor system may be involved; the decrease in cAMP content may be due to an inhibition of the beta stimulatory action of catecholamines on adenylate cyclase.
 ...
PMID:Effect of halothane on myocardial cyclic AMP and cyclic GMP content of mice. 286 13

The role of G proteins in mediating adrenoceptor-prostacyclin synthesis coupling was investigated using the G protein activator, sodium fluoride. Sodium fluoride (NaF) stimulated in vitro rat aortic prostacyclin (PGI2) synthesis (EC50 = 5 x 10(-3) mol.l-1), an action inhibited completely by the presence of EDTA (10(-2) mol.l-1). The NaF-PGI2 dose-response curve was moved to the left by the presence of adrenaline, phorbol 12,13-dibutyrate (PDBU) and the Ca2+ ionophore A23187 in the incubation media. NaF-stimulated (5 x 10(-3) mol.l-1) PGI2 synthesis was inhibited by the Ca2+ channel blockers, verapamil and nifedipine, the protein kinase C inhibitor, H7, and lanthanum. Prazosin and yohimbine were without effect on NaF action, but partially inhibited adrenaline-potentiated NaF-stimulated PGI2 synthesis. Cyclic adenosine-3',5'-monophosphate (cAMP) and dibutyryl cAMP were without effect on de novo or NaF-, adrenaline-, PDBU- or A23187-stimulated PGI2 synthesis. Since fluoride is known to stimulate adenyl cyclase and phospholipase C, these data suggest that: (1) NaF stimulates in vitro rat aortic PGI2 synthesis by initiating Ca2+ influx; (2) this Ca2+ influx is mediated by protein kinase C, probably through G protein activation of phospholipase C and the generation of the protein kinase C activator, diacyl glycerol; and (3) adenyl cyclase and protein kinase A are not involved in NaF-stimulated PGI2 synthesis by the rat aorta.
 ...
PMID:Fluoride stimulates in vitro vascular prostacyclin synthesis: interrelationship of G proteins and protein kinase C. 313 Nov 47

Three types of adrenergic receptors, beta, alpha-1, and alpha-2, were identified in human adipocytes, isolated from properitoneal adipose tissue, using both the binding of radioactive ligands and the effects of adrenergic agents on receptor-specific biochemical responses. Adrenergic binding studies showed the following results: [(3)H]dihydroalprenolol binding (beta adrenergic) B(max) 280 fmol/mg protein, K(D) 0.38 nM; [(3)H]para-aminoclonidine binding (alpha-2 adrenergic) B(max) 166 fmol/mg protein, K(D) 0.49 nM; [(3)H]WB 4101 binding (alpha-1 adrenergic) B(max) 303 fmol/mg protein, K(D) 0.86 nM. In adipocytes from subcutaneous adipose tissue, [(3)H]dihydroergocryptine binding indicated the presence of alpha-2 but not alpha-1 receptors. Beta and alpha-2 adrenergic receptors appeared to be positively and negatively coupled to adenylate cyclase, respectively. Cells or cell membranes were incubated with epinephrine (10 muM) alone and in combination with the antagonists yohimbine (alpha-2) and prazosin (alpha-1). Epinephrine alone prompted a modest increase in adenylate cyclase activity, cyclic AMP, and glycerol release, an index of lipolysis. Yohimbine (0.1 muM) greatly enhanced these actions whereas prazosin was without effect. The beta agonist, isoproterenol, stimulated glycerol release, whereas the alpha-2 agonist, clonidine, inhibited lipolysis and cyclic AMP accumulation. To assess further alpha-1 receptors, cells were incubated with [(32)P]phosphate and epinephrine (10 muM) alone and in combination with prazosin and yohimbine. Epinephrine alone caused a three- to fourfold increase in (32)P incorporation into phosphatidylinositol. Prazosin (0.1 muM) blocked this action whereas yohimbine (0.1 muM) was without effect. Thus, in a homogeneous cell preparation, the human adipocyte appears to have three different adrenergic receptors, each of which is coupled to a distinct biochemical response.
 ...
PMID:Pharmacological characterizations of adrenergic receptors in human adipocytes. 625 62

alpha-Adrenergic receptor stimulation regulates the activity of a number of different cardiac ion channels, including those underlying one or more distinct Cl- conductances. The whole-cell patch-clamp technique was used in the present study to investigate the effects of alpha-adrenergic stimulation on the beta-adrenergically regulated Cl- current in guinea pig ventricular myocytes. Neither alpha 1-adrenergic receptor stimulation with methoxamine (25 to 500 mumol/L) nor direct activation of endogenous protein kinase C (PKC) with phorbol 12,13-dibutyrate (PDBu, 100 nmol/L) evoked a Cl- current. On the contrary, the Cl- current activated by 30 nmol/L isoproterenol was inhibited by methoxamine, with an EC50 of 6.7 +/- 2.6 mumol/L, and this response was blocked by prazosin, an alpha 1-adrenergic receptor antagonist. Prazosin also decreased the EC50 for current activation by norepinephrine from 53 +/- 7.1 to 18 +/- 3.8 nmol/L, demonstrating that the ability of this endogenous neurotransmitter to activate the Cl- current through beta-adrenergic receptor stimulation is limited by its intrinsic ability to also activate alpha-adrenergic receptors. Methoxamine did not inhibit the Cl- current evoked by either direct activation of adenylate cyclase with forskolin or inhibition of phosphodiesterase activity with 3-isobutyl-1-methylxanthine, indicating that alpha-adrenergic stimulation inhibits beta-adrenergic responses at a point upstream of adenylate cyclase activation. Methoxamine also did not inhibit the Cl- current activated by histamine, suggesting that alpha-adrenergic stimulation specifically inhibits beta-adrenergic receptor-mediated responses. The inhibitory effect of methoxamine was not mimicked by PDBu, and it persisted in the presence of bisindolylmaleimide, a selective PKC inhibitor. However, methoxamine inhibition of the isoproterenol-activated Cl- current was sensitive to pertussis toxin. These results suggest that alpha-adrenergic receptor stimulation inhibits the beta-adrenergically activated Cl- current, demonstrating a novel mechanism by which alpha-adrenergic receptors may regulate ion channel activity in the heart.
 ...
PMID:Alpha 1-adrenergic inhibition of the beta-adrenergically activated Cl- current in guinea pig ventricular myocytes. 863 40

Alpha 1 adrenoceptor (alpha1-AR) regulation of DNA synthesis was studied in human neonatal foreskin fibroblast. Saturation assay with a specific radioligand for alpha1 adrenergic [3H]-prazosin revealed two saturated and specific binding sites with high or low affinity. Competitive binding assay with different antagonist subtypes, defined pharmacologically three major types of alpha1-AR. The alpha1-AR agonists (from 1x10(-10) to 1x10(-4) M) triggered a biphasic action on DNA synthesis reaching maximal stimulation at 1x10(-9) M and maximal inhibition at 1x10(-6) M. Prazosin, abolished the stimulatory (pA2: 9.24) and inhibitory (pA2: 8.80) actions of alpha1-AR agonists. The alpha1-AR stimulation resulted in the activation of phosphoinositide turnover (InsP) via phospholipase C (PLC) involving calcium/calmodulin (CaM) and nitric oxide synthase (NOS) that correlates with the DNA synthesis increment; whereas the inhibition resulted in a decrease of cyclic AMP (cAMP) accumulation via adenylate cyclase inhibition. The potency displayed by the specific antagonists tested in binding, DNA synthesis, InsP and NOS at low agonist concentration suggests that they can be elicited by the activation of the same receptor (alpha1B-AR subtype); while the decrement in DNA synthesis and cAMP at high concentration account by the activation of alpha1D-AR coupled to Gi protein. Non-functional alpha1A-AR in neonatal human foreskin fibroblast was observed. Results suggest that the expression of alpha1-AR subtypes on human skin fibroblast may differentially activate signaling pathways that modulate physiological response of the cells.
 ...
PMID:Differential regulation on human skin fibroblast by alpha1 adrenergic receptor subtypes. 1771 96