Atrial natriuretic factor ameliorates chronic metabolic alkalosis by increasing glomerular filtration

The kidney maintains the elevated plasma concentration of bicarbonate that occurs in chronic metabolic alkalosis. A reduction in the glomerular filtration rate (GFR) can maintain the filtered bicarbonate load at a normal level so that a normal rate of bicarbonate reabsorption suffices to prevent urinary excretion of this anion. It is also possible that bicarbonate reabsorption might increase so as to maintain the alkalosis if GFR were not reduced. To examine this latter possibility, atrial natriuretic factor was used in alkalotic rats to restore a more normal GFR and to increase the amount of bicarbonate filtered by the glomerulus. Proximal bicarbonate reabsorption remained relatively static. Higher than normal amounts of bicarbonate were then delivered out of the proximal tubule, bicarbonate appeared in the urine, and the plasma concentration of bicarbonate fell. A reduction in GFR is thus necessary for the maintenance of chronic metabolic alkalosis. Normalizing GFR induces bicarbonaturia and initiates repair of the alkalosis.     

Atrial natriuretic peptide elevation in congestive heart failure in the human

A sensitive radioimmunoassay for atrial natriuretic peptide was used to examine the relation between circulating atrial natriuretic peptide and cardiac filling pressure in normal human subjects, in patients with cardiovascular disease and normal cardiac filling pressure, and in patients with cardiovascular disease and elevated cardiac filling pressure with and without congestive heart failure. The present studies establish a normal range for atrial natriuretic peptide in normal human subjects. These studies also establish that elevated cardiac filling pressure is associated with increased circulating concentrations of atrial natriuretic peptide and that congestive heart failure is not characterized by a deficiency in atrial natriuretic peptide, but with its elevation.     

Allosteric activation of a spring-loaded natriuretic peptide receptor dimer by hormone

Natriuretic peptides (NPs) are vasoactive cyclic-peptide hormones important in blood pressure regulation through interaction with natriuretic cell-surface receptors. We report the hormone-binding thermodynamics and crystal structures at 2.9 and 2.0 angstroms, respectively, of the extracellular domain of the unliganded human NP receptor (NPR-C) and its complex with CNP, a 22-amino acid NP. A single CNP molecule is bound in the interface of an NPR-C dimer, resulting in asymmetric interactions between the hormone and the symmetrically related receptors. Hormone binding induces a 20 angstrom closure between the membrane-proximal domains of the dimer. In each monomer, the opening of an interdomain cleft, which is tethered together by a linker peptide acting as a molecular spring, is likely a conserved allosteric trigger for intracellular signaling by the natriuretic receptor family.     

Leukotactic factor produced by sensitized lymphocytes

Lymph node lymphocytes obtained from guinea pigs exhibiting delayed hypersensitivity are stimulated in vitro by specific antigen to produce a soluble factor that is chemotactic in vitro for mononuclear macrophages. The material is nondialyzable, relatively heat stable, and elutes from Sephadex G-100 in the fraction containing molecules smaller than immunoglobulins.     

Inhibition of vasopressin action by atrial natriuretic factor

Atrial natriuretic factor results in diuresis in animals and humans, perhaps because atrial natriuretic factor increases renal blood flow. The possibility that this diuresis is due to direct inhibition of renal tubular epithelial water transport was examined in rabbit collecting tubules perfused in vitro. Atriopeptin III inhibition of the hydraulic conductivity response to the hormone arginine vasopressin but not to either 3'5'-cyclic adenosine monophosphate or forskolin was found. These results suggest that atriopeptin III acts proximal to cyclic adenosine monophosphate formation to directly affect vasopressin-stimulated water transport in the mammalian nephron. They also suggest a potential role for inhibition by atrial natriuretic factor of the renal response to arginine vasopressin as a contributor to a diuretic state.     

The structure of rat preproatrial natriuretic factor as defined by a complementary DNA clone

The structure of rat preproatrial natriuretic factor ( preproANF ) was determined by nucleotide sequence analysis of an ANF complementary DNA clone. PreproANF is composed of a hydrophobic leader segment (20 amino acids), a precursor containing one glycosylation site (106 amino acids), and ANF (24 amino acids). Atrial natriuretic factor is located at the carboxyl terminus of the precursor molecule. The human, mouse, and rat genomes each contain a single ANF gene which is highly conserved.     

Atrial natriuretic peptide inhibits a cation channel in renal inner medullary collecting duct cells

The patch-clamp technique was used to examine the effects of atrial natriuretic peptide (ANP) and its second messenger guanosine 3',5'-monophosphate (cGMP) on an amiloride-sensitive cation channel in the apical membrane of renal inner medullary collecting duct cells. Both ANP (10(-11) M) and dibutyryl guanosine 3',5'-monophosphate (10(-4) M) inhibited the channel in cell-attached patches, and cGMP (10(-5) M) inhibited the channel in inside-out patches. The inner medullary collecting duct is the first tissue in which ANP, via its second messenger cGMP, has been shown to regulate single ion channels. The results suggest that the natriuretic action of ANP is related in part to cGMP-mediated inhibition of electrogenic Na+ absorption by the inner medullary collecting duct.     

Biosynthesis and secretion of proatrial natriuretic factor by cultured rat cardiocytes

Rat atrial natriuretic factor (ANF) is translated as a 152-amino acid precursor preproANF. PreproANF is converted to the 126-amino acid proANF, the storage form of ANF in the atria. ANF isolated from the blood is approximately 25 amino acids long. It is demonstrated here that rat cardiocytes in culture store and secrete proANF. Incubation of proANF with serum produced a smaller ANF peptide. PreproANF seems to be processed to proANF in the atria, and proANF appears to be released into the blood, where it is converted by a protease to a smaller peptide.     

哈维氏弧菌的主要致病因子及其特性分析

从大黄鱼致病菌哈维氏弧菌(Vibrio harveyi)GYC1108-1株提取外膜蛋白(OMP)、脂多糖(LPS)和胞外产物(ECP),并进行毒性实验,以研究哈维氏弧菌的主要致病因子及其特征.结果表明:OMP、LPS致病性较弱,而ECP可导致鱼死亡,初步得出哈维氏弧菌GYC1108-1株的主要致病因子为胞外产物,其对鱼的半数致死量(LD50)为3.5 μg·g-1;该蛋白酶与底物偶氮酪蛋白(azocasein)作用的最适pH为8.0,最适温度28℃,对热敏感,分子质量为55 ku;该酶活性被碘乙酸抑制,也被SDS和HgCl2完全抑制,PMSF和ZnCl2能部分抑制该蛋白酶活性,而CuCl2、CaCl2、MgCl2对该酶活性影响不大,2-巯基乙醇、DTT、L-半胱氨酸、EDTA和EGTA对该酶活性有促进作用,表明其为半胱氨酸蛋白酶;研究发现ECP具有酪蛋白酶、明胶蛋白酶、淀粉酶、卵磷脂酶和脂肪酶活性,无脲酶活性;免疫印迹结果发现GYC1108-1的ECP能与大黄鱼抗GYC1108-1血清发生免疫发应,分子质量为55 ku的半胱氨酸蛋白酶是具有免疫原性的物质.     

Thyrotropin releasing hormone: enhancement of dopa activity by a hypothalamic hormone

Thyrotropin releasing hormone potentiates the behaviorial effects of dopa plus pargyline in mice. Because the potentiation occurs in hypophysectomized mice, as well as in normal mice, the phenomenon is independent of the release of thyroid stimulating hormone from the pituitary. Possible mechanisms and clinical implications are discussed.     

Enstatite: disorder produced by a megabar shock event

Shocked Bamle enstatite partly transforms to disordered enstatite. Debye-Scherrer patterns of some shocked material are almost identical to those of disordered enstatite from portions of various enstatite achondrites. No disorcdered single crystals have been found.     

Pineal vasotocin: release into cat cerebrospinal fluid by melanocyte-stimulating hormone release-inhibiting factor

The intracarotid injection of both synthetic melanocyte-stimulating hormone release-inhibiting factor (MIF) and purified MIF prepared from bovine hypothalami induces arginine vasotocin release into cerebrospinal fluid of cats and significantly decreases the pineal arginine vasotocin content at 5 minutes after the injection. The present results demonstrate an extrapituitary endocrine effect of synthetic and purified bovine MIF.     

Nucleotide sequences of the human and mouse atrial natriuretic factor genes

Mouse and human atrial natriuretic factor (ANF) genes have been cloned and their nucleotide sequences determined. Each ANF gene consists of three coding blocks separated by two intervening sequences. The 5' flanking sequences and those encoding proANF are highly conserved between the two species, while the intervening sequences and 3' untranslated regions are not. The conserved sequences 5' of the gene may play an important role in the regulation of ANF gene expression.     

Inhibition of adrenocorticotropic hormone secretion in the rat by immunoneutralization of corticotropin-releasing factor

Intravenous administration of rabbit antiserum to ovine corticotropin-releasing factor (CRF) markedly reduced the CRF-induced rise of plasma adrenocorticotropic hormone (ACTH) in intact nonstressed adult male rats while blocking more than 75 percent of the ACTH release observed in rats exposed to ether stress. Furthermore, antiserum to CRF significantly lowered ACTH levels in adrenalectomized animals. These results suggest that endogenous CRF plays a physiological role in regulating ACTH secretion.     

Coexistence of guanylate cyclase and atrial natriuretic factor receptor in a 180-kD protein

Atrial natriuretic factor (ANF) is a peptide hormone that is released from atria and regulates a number of physiological processes, including steroidogenesis in adrenal cortex and testes. The parallel stimulation of membrane guanylate cyclase and corticosterone production in isolated fasciculata cells of rat adrenal cortex has supported the hypothesis of a mediatory role for cyclic guanosine monophosphate (cyclic GMP) in signal transduction. A novel particulate guanylate cyclase tightly coupled with ANF receptor was purified approximately 273,000-fold by two-step affinity chromatography. The enzyme had a molecular size of 180 kilodaltons and was acidic in nature with a pI of 4.7. Its specific activity was 1800 nanomoles of cyclic GMP formed per minute per milligram of protein. The purified enzyme bound ANF with a specific binding activity of 4.01 nanomoles per milligram of protein, a value that is close to the theoretical binding activity of 5.55 nanomoles per milligram of protein for 1 mole of the ligand binding 1 mole of the receptor protein. These results indicate that the guanylate cyclase-coupled ANF receptor exists in a 180-kilodalton protein of rat adrenocortical carcinoma and represent a step toward the elucidation of the basic mechanism of cyclic GMP-mediated transmembrane signal transduction in response to a hormone.     

Cerebral hydroxylases: stimulation by a new factor

Cerebral tryptophan 5-hydroxylase and tyrosine hydroxylase are stimulated by a solution of lyophilized, protein-free 30,000g supernatant of brain homogenates (concentrate 1). This preparation can be further purified by passage through Sephadex G-75 and phosphocellulose columns to yield concentrate 2. Unlike concentrate 1, concentrate 2 is unstable after several days of storage even at -27 degrees C. Neither preparation is active without the presence of a reduced pteridine cofactor. The stimulating factor appears to be thermostable, alkali-labile, dialyzable, and light-sensitive.     

Dopamine synthesis: stimulation by a hypothalamic factor

The effect of treatment with the factor that inhibits the release of melanocyte stimulating hormone (MSH) identified as 1-prolyl-1-leucylglycinamide (MIF) on brain catecholamine synthesis was examined in normal and hypophysectomized rats. The tripeptide induced a dose-related increase in striatal dopamine synthesis in slices obtained from treated normal animals but not in hypophysectomized animals. Hypothalamic norepinephrine synthesis was unaltered by MIF treatment in normal as well as in hypophysectomized rats. In addition, dopamine and norepinephrine syntheses were depressed in untreated hypophysectomized animals, as compared to normal controls. These results constitute the first direct demonstration of a central neurochemical effect of a hypothalamic factor.