Abstract The endogenous ligand for the GH secretagogue receptor is ghrelin, a peptide recently purified from stomach. Ghrelin n-octanoylated on Ser3 residue, and this modification essential its interaction with receptor. degradation of ghrelin by rat human serum, commercial enzymes, tissues homogenates was analyzed combining HPLC mass spectrometry. In desoctanoylated, without proteolysis. desoctanoylation significantly reduced phenylmethylsulfonyl fluoride, serine proteases esterases...

To compare the proportions of four muscarinic receptors in different rat brain regions, we used competition curves with selective antagonists, at 1-[N-methyl-3H]scopolamine methyl chloride [( 3H]NMS) binding equilibrium and after allowing [3H]NMS dissociation for 35 min. Himbacine methoctramine were shown to discriminate two receptor subtypes having a high affinity 4-diphenylacetoxy-N-methylpiperidine methiodide hexahydrosiladifenidol, intermediate pirenzepine, low AF-DX 116. One M4 subtype...

Adenylate cyclase stimulation by GH-releasing factor (GRF) and 14 GRF analogs (modified in the N-terminalpart) was compared to capacity of same peptides toinhibit [125I]iodo-vasoactive intestinal peptide (VIP) binding inrat pancreatic plasma membranes. These interferedwith VIP receptors as they inhibited [12SI]iodo-VIP binding, andprobably acted through VIP-preferring one thesepeptides [(N-Ac-Tyr1,D-Phe2)-GRF(l-29)-NH2] selectively inhibitedboth VIP- GRF-stimulated adenylate activities. In...

The binding properties of muscarinic cholinergic sites were investigated in rat cardiac membranes, using the labeled agonist [3H] oxotremorine-M ([3H]Oxo-M) and antagonist L-[benzilic-4,4'-3H]quinuclidinyl benzilate (L-[3H]QNB). both tracers was inhibited stereospecifically by dexetimide levitimide. [3H]Oxo-M only high-affinity sites, whereas L-[3H]QNB bound to high- low-affinity with equal affinity. Agonists unable induce "negative cooperativity" interactions increasing dissociation or...

The efficacy and potency of 14 GH-releasing factor (GRF) analogs, substituted in position 1 to 7, on adenylate cyclase activation crude homogenates from rat anterior pituitary were related those human pancreatic GRF(l–29)–amide vasoactive intestinal peptide. Among several d–amino acid substitutions, that 2 was the only one yield a super–agonist [with Kact (concentration required for half–maximal activation) times lower than GRF(l–29)–NH2]. By contrast, d–isomer substitution 3 without effect...

We mutated the vasoactive intestinal peptide (VIP) Asp3 residue and two VPAC1receptor second transmembrane helix basic residues (Arg188and Lys195). VIP had a lower affinity for R188Q, R188L, K195Q, K195I VPAC1 receptors than receptors. [Asn3] [Gln3] affinities but higher mutant receptors; amino acids facilitated introduction of negatively charged aspartate inside domain. The resulting interaction was necessary receptor activation. 1/[Asn3] were partial agonists at 2/VIP did not fully...

Insulin binding to its cellular receptors is markedly dependent on the temperature. The thermodynamic parameters for reaction of insulin with high affinity state receptor have been evaluated equilibrium studies at multiple temperatures between 5 degrees and 37 C. thermodynamics insulin-receptor interaction not classical. van't Hoff plot linear. Both enthalpy entropy changes, due formation hormone . complex, decrease temperature, corresponding a large heat capacity change -766 cal/(mol deg)...

Beta-adrenergic receptors were characterized in a particulate fraction of human auricles obtained from patients operated upon for coronary insufficiency or valvular disease. [125I] Hydroxybenzylpindolol binding was evaluated terms kinetics; KD and Bmax values; inhibition the presence 10 microM GTP increasing concentrations four nonselective agonists giving Hill coefficient 1 (isoproterenol, salbutamol, fenoterol, epinephrine), two antagonists (pindolol propranolol), series selective drugs...

A combination of three HPLC procedures applied to the venom Gila monster (Heloderma suspectum) has led purification homogeneity two bioactive components: (i) a 17.5 kDa protein, isolated on basis its potent secretory effect dispersed rat pancreatic acini, was accordingly designated PSF (pancreatic factor); (ii) 5.9-kDa peptide, helodermin, purified ability stimulate adenylate cyclase in membranes. unable activate and, conversely, helodermin devoid action.

We compared the binding of [N-methyl-3H]scopolamine methyl chloride [( 3H]NMS) and pirenzepine to muscarinic receptors in four regions rat central nervous system (cortex, hippocampus, striatum, cerebellum) heart. Equilibrium studies suggested existence three classes receptors: A, with high affinity for [3H] NMS (in cortex, striatum); B, intermediate [3H]NMS same brain regions); C, low cerebellum heart). Dissociation kinetic indicated that receptor types C had different koff values allowing,...

The beta-adrenergic stimulation of adenylate cyclase in membranes from human auricles, ventricles, and fetal heart was compared with the binding properties receptors auricles. In terms activation, three full agonists (isoproterenol, epinephrine, norepinephrine), four partial (procaterol, salbutamol, fenoterol, zinterol), antagonists (propranolol, metoprolol, atenolol, practolol) were tested. activation rat (with a majority beta 1-adrenergic receptors), erythrocytes, reticulocytes homogeneous...

d-Tubocurarine behaved as a weak allosteric inhibitor of N-[3H] methylscopolamine binding to cardiac M2 muscarinic receptors. In low ionic strength buffer devoid bivalent ions, d-tubocurarine recognized receptors in the micromolar concentration range and decreased their affinity for N-[3H]methylscopolamine by at most 4-fold. To identify compounds that preferentially recognize this accessory site (as opposed classical site), we measured inhibition different drugs binding, absence or presence...

We previously observed that [3H]NMS recognizes three types of muscarinic receptors in rat brain (one M1 subclass with high affinity for pirenzepine, and two M2 subclasses low affinities pirenzepine), based on distinct kinetic constants these subclasses. In this work, we investigated the binding four selective antagonists to (the M2) were able demonstrate cardiac-like pirenzepine N-methylscopolamine present not only cerebellum (as shown; see introduction) but also cortex, striatum,...