Parathyroid hormone: a coronary artery vasodilator.

Injection of synthetic bovine parathyroid hormone (the amino terminal peptide containing the first 34 amino acids) to the coronary circulation of the dog resulted in a marked coronary vasodilation. The vasodilatory response was dose-dependent and amounted to a 161 percent increase over the resting flow rate at a concentration of 1.0 unit per kilogram.

Vasopressin analogs that antagonize antidiuretic responses by rats to the antidiuretic hormone.

Four new synthetic analogs of vasopressin (antidiuretic hormone) can antagonize the antidiuretic response to intravenous vasopressin in anesthetized, water-loaded rats. They also cause a diuresis resembling that of diabetes insipidus when given intraperitoneally to conscious rats. Such antagonists may prove to be useful both pharmacologically and therapeutically.

Respiratory virus infection among hospitalized adult patients with or without clinically apparent respiratory infection: a prospective cohort study.

OBJECTIVES: To determine the viral epidemiology and clinical characteristics of patients with and without clinically apparent respiratory tract infection. METHODS: This prospective cohort study was conducted during the 2018 winter influenza season. Adult patients with fever/respiratory symptoms (fever/RS group) were age- and sex-matched with patients without fever/RS (non-fever/RS group) in a 1:1 ratio. Respiratory viruses were tested using NxTAG™ Respiratory Pathogen Panel IVD, a commercially-available multiplex PCR panel. RESULTS: A total of 214 acutely hospitalized patients were included in the final analysis, consisting of 107 with fever/RS (fever/RS group), and 107 age- and sex-matched patients without fever/RS (non-fever/RS group). Respiratory viruses were detected in 34.1% (73/214) of patients, and co-infection occurred in 7.9% (17/214) of patients. The incidence of respiratory virus was higher in the fever/RS group than in the non-fever/RS group (44.9% (48/107) versus 23.4% (25/107), p 0.001). Influenza B virus, enterovirus/rhinovirus and coronaviruses were detected more frequently in the fever/RS group, whereas parainfluenza virus 4B and adenovirus were detected more frequently in the non-fever/RS group. Among the non-fever/RS group, chest discomfort was more common among patients tested positive for respiratory viruses than those without respiratory virus detected (44% (11/25) versus 22% (18/82), p 0.04). CONCLUSIONS: Respiratory viruses can be frequently detected among hospitalized patients without typical features of respiratory tract infection. These patients may be a source of nosocomial outbreaks.

Saliva as a diagnostic specimen for testing respiratory virus by a point-of-care molecular assay: a diagnostic validity study.

OBJECTIVES: Automated point-of-care molecular assays have greatly shortened the turnaround time of respiratory virus testing. One of the major bottlenecks now lies at the specimen collection step, especially in a busy clinical setting. Saliva is a convenient specimen type that can be provided easily by adult patients. This study assessed the diagnostic validity, specimen collection time and cost associated with the use of saliva. METHODS: This was a prospective diagnostic validity study comparing the detection rate of respiratory viruses between saliva and nasopharyngeal aspirate (NPA) among adult hospitalized patients using Xpert® Xpress Flu/RSV. The cost and time associated with the collection of saliva and nasopharyngeal specimens were also estimated. RESULTS: Between July and October 2017, 214 patients were recruited. The overall agreement between saliva and NPA was 93.3% (196/210, κ 0.851, 95% CI 0.776-0.926). There was no significant difference in the detection rate of respiratory viruses between saliva and NPA (32.9% (69/210) versus 35.7% (75/210); p 0.146). The overall sensitivity and specificity were 90.8% (81.9%-96.2%) and 100% (97.3%-100%), respectively, for saliva, and were 96.1% (88.9%-99.2%) and 98.5% (94.7%-99.8%), respectively, for NPA. The time and cost associated with the collection of saliva were 2.26-fold and 2.59-fold lower, respectively, than those of NPA. CONCLUSIONS: Saliva specimens have high sensitivity and specificity in the detection of respiratory viruses by an automated multiplex Clinical Laboratory Improvement Amendments-waived point-of-care molecular assay when compared with those of NPA. The use of saliva also reduces the time and cost associated with specimen collection.

Glucose-induced alterations of cytosolic free calcium in cultured rat tail artery vascular smooth muscle cells.

We have previously suggested that hyperglycemia per se may contribute to diabetic hypertensive and vascular disease by altering cellular ion content. To more directly investigate the potential role of glucose in this process, we measured cytosolic free calcium in primary cultures of vascular smooth muscle cells isolated from Sprague-Dawley rat tail artery before and after incubation with 5 (basal), 10, 15, and 20 mM glucose. Glucose significantly elevated cytosolic free calcium in a dose- and time-dependent manner, from 110.0 +/- 5.4 to 124.5 +/- 9.0, 192.7 +/- 20.4, and 228.4 +/- 21.9 nM at 5, 10, 15, and 20 mM glucose concentrations, respectively. This glucose-induced cytosolic free calcium elevation was also specific, no change being observed after incubation with equivalent concentrations of L-glucose or mannitol. This glucose effect was also dependent on extracellular calcium and pH, since these calcium changes were inhibited in an acidotic or a calcium-free medium, or by the competitive calcium antagonist lanthanum. We conclude that ambient glucose concentrations within clinically observed limits may alter cellular calcium ion homeostasis in vascular smooth muscle cells. We suggest that these cellular ionic effects of hyperglycemia may underlie the predisposition to hypertension and vascular diseases among diabetic subjects and/or those with impaired glucose tolerance.

Identification and characterization of parathyroid hormone receptors in rat renal cortical plasma membranes using radioligand binding.

Parathyroid hormone (PTH) receptors have been described in renal tissue from several species, but not in the rat. In this study, radioligand binding techniques were used to identify and characterize PTH receptors in rat kidney cortical membranes. The sulfur-free PTH analog [Nle8,18Tyr34]bovine PTH-(1-34)amide was iodinated using the iodogen method. This ligand was suitable for use in identifying PTH receptors in canine renal membranes, but not rat renal membranes. Synthetic, unsubstituted rat PTH-(1-34) was iodinated using the milder, lactoperoxidase technique and was purified by HPLC on a C8 column. [125I]rat PTH-(1-34) bound rapidly to both rat and dog renal membranes. At 22 degrees C reaction reached steady state within 20 minutes, and this level was maintained for at least 3 h. Specific binding was routinely greater than 90% for rat kidney and greater than 95% for dog kidney. Similar results were obtained at 4 degrees C with a longer time required to attain steady state (approximately 45 minutes). Binding was reversible as demonstrated by dissociation of bound ligand after either infinite dilution or displacement with excess nonradioactive PTH. Binding was saturable and of high affinity (rat kidney: Bmax = 2.3 pmol/mg protein, Kd = 3.1 nM, dog kidney: Bmax = 2.1 pmol/mg protein, Kd = 3.7 nM). Rat renal cortical adenylate cyclase activity was stimulated by rat PTH in a dose-dependent manner with an EC50 of 4 nM, a value in good agreement with the binding data. This study demonstrates the feasibility of identifying and characterizing parathyroid hormone receptors in rat renal cortical plasma membranes using radioligand binding techniques.

Calcium mobilization and isometric tension in bovine tracheal smooth muscle: effects of salbutamol and histamine.

We determined if decreases in relative free intracellular calcium concentration ([Ca2+]i) caused by salbutamol, a selective beta2-adrenoreceptor agonist, were paralleled by calcium egression from the cytosol in bovine trachealis muscle strips. [Ca2+]i, or tissue-surface extracellular calcium changes (Ts[Ca2+]ext), were monitored using Fluo-3 acetoxymethylester or Fluo-3 pentaammonium salt simultaneously with isometric tension. Salbutamol (1 microM) decreased histamine-induced isometric tension from an average peak tension of 128.5 +/- 18.4 to -4.9 +/- 0.3 mN/mm2, and reduced the associated sustained increases in [Ca2+]i from 100% at peak to 20.4 +/- 7.6%. Both histamine-induced elevation in [Ca2+]i and isometric tension were reversed completely by forskolin (1 microM). In muscle strip at active resting tension, salbutamol caused a decrease (49.6 +/- 12.1%) in [Ca2+]i. Following precontraction with histamine, salbutamol caused an immediate and sustained increase in Ts[Ca2+]ext which was not seen in a Na(+)-free solution. Finally, propranolol (10 microM) blocked both increases in Ts[Ca2+]ext and muscle relaxation caused by salbutamol. These findings indicate that in bovine trachealis muscle, the effect of salbutamol to decrease [Ca2+]i and isometric tension is via a beta2-adrenoceptor, and the changes in [Ca2+]i are by an increase in calcium egression via the Na(+)/Ca2+ exchanger, and reuptake by myoplasmic stores.

Enhanced calcium influx by parathyroid hormone in identified Helisoma trivolvis snail neurons.

The modulation of [Ca2+]i by parathyroid hormone (PTH) has been extensively studied in vertebrates. The present study examined the effects of PTH on [Ca2+]i in isolated invertebrate neurons B5 from buccal ganglia of the pond snail, Helisoma trivolvis, utilizing the Fura-2 fluorescence technique. Bovine PTH, bPTH-(1-84), induced a slow and sustained increase in [Ca2+]i in neurons B5. In contrast, the elevation of extracellular K+ concentration from 1.7 mM to 15 mM induced a rapid and transient increase in [Ca2+]i. Simultaneous application of 15 mM KCl and bPTH-(1-84), or application of 15 mM KCl in the presence of bPTH-(1-84) additively increased [Ca2+]i in neurons B5. An increase in [Ca2+]i in neurons B5 was also induced by a PTH agonist [bPTH-(1-34)], but not by a PTH antagonist [bPTH-(3-34)]. The absence of calcium, or the presence of lanthanum (2 mM) or omega-conotoxin (10 microM), in the bath solution abolished the effect of bPTH-(1-84) on [Ca2+]i. Furthermore, our results demonstrated that the effect of PTH on [Ca2+]i in neurons B5 was not due to the hormonal modulation of voltage-dependent Na+ or K+ channels or a Na+/Ca2+ exchanger. The results from this study show that PTH can modulate [Ca2+]i in an identified invertebrate neuron mainly by promoting extracellular calcium influx via the N-like voltage-dependent calcium channel.

Parathyroid hormone messenger ribonucleic acid in the rat hypothalamus.

Polyadenylated RNA, extracted from rat hypothalami, cross-hybridized with a RNA probe complementary in sequence to rat PTH (rPTH) messenger RNA (mRNA). Amplification of complementary DNA (cDNA) by the polymerase chain reaction also demonstrated the presence of rPTH mRNA in the rat hypothalamus and parathyroid gland. rPTH mRNA was localized by in situ hybridization in the paraventricular and supraoptic nuclei of the rat hypothalamus. These results demonstrate the expression of the PTH gene in the central nervous system of the rat in areas which suggest roles for PTH in neuroendocrine function.

Structure activity relationship of parathyroid hormone: separation of the hypotensive and the hypercalcemic properties.

The present study was conducted to show that the hypercalcemic and the vascular relaxing activities of PTH are two separable properties. During the hypotensive action of the synthetic fragment bovine (b) PTH-(1-34), plasma calcium levels were not significantly changed. Mild oxidation with hydrogen peroxide abolished the hypotensive and hypercalcemic actions of bPTH-(1-84). However, the same treatment on bPTH-(1-34) abolished only the hypotensive and not the hypercalcemic action. Analysis of the amino acid composition revealed only the oxidation of the methionines to methionine sulfoxides. The other amino acids remained unchanged. In addition, the analog with methionines replaced by norleucine, [Nle8,Nle18,Tyr34]bPTH-(1-34), was active in all the vascular assays, and these activities were unaffected by hydrogen peroxide treatment of the molecule. Perhaps the methionine sulfoxides in the hydrogen peroxide-treated bPTH-(1-34) affected the changes of the molecule in such a manner that the part of the molecule for the vascular action but not that for the hypercalcemic action was no longer accessible to the receptors of the target organs. The hypotensive pentapeptide, bPTH-(24-28), was not active in the hypercalcemic assay. All these data are consistent with our hypothesis that the vascular relaxing and the hypercalcemic actions of PTH are two separate properties of the molecule.

The role of calcium in prolactin release from the pituitary of a teleost fish in vitro.

The release of PRL from the pituitary of a teleost fish, the tilapia (Oreochromis mossambicus), has been previously shown to be dependent on calcium. However, the source(s) and specific action(s) of calcium in the secretory process have not been identified. Also undefined are the mechanisms by which regulators of PRL cell function may alter calcium distribution. In the present investigation, the elevation of medium K+ concentration during static incubations to a depolarizing concentration (56 mM) produced no change in cumulative PRL release over control levels during the 18-20 h of incubation. During perifusion incubation, exposure to high K+ concentrations briefly stimulated (less than or equal to 10 min) and then depressed PRL release. In contrast, reduced medium osmotic pressure elicited a rapid elevation in PRL release that was sustained for 2 h or more. D600, a calcium entry blocker, at 10(-5) M diminished the K+-induced pulses of PRL release. The same concentration, however, did not alter the release of PRL evoked by reduced osmotic pressure. In contrast, CoCl2, which blocks a range of calcium-mediated processes in addition to calcium influx, suppressed PRL release during perifusion and static incubations in hyposmotic medium. These findings suggest that while PRL secretion from the tilapia pituitary is calcium dependent, calcium entry through voltage-regulated plasmalemma channels may not be a prerequisite to the actions of reduced osmotic pressure.

Effects of dehydroepiandrosterone sulfate on cellular calcium responsiveness and vascular contractility.

Dehydroepiandrosterone sulfate (DHEAS) is an endogenous steroid having a wide variety of biological effects, but its physiological role remains undefined. Since an age-related decline of DHEAS corresponds to the progressive onset of atherosclerosis, cardiovascular diseases, and overall mortality, we investigated a possible protective role of DHEAS in vascular disease by studying the effects of this hormone (10(-7) to 10(-5) mol/L) on cytosolic free calcium and contractility in different in vitro vascular tissue preparations. DHEAS produced a significant, dose-dependent relaxation of isolated helical strips of rat tail artery precontracted with KCl (60 mmol/L) (89.7 +/- 18.7%, P < .01), arginine vasopressin (3 nmol/L) (27.3 +/- 7.1%, P < .01), and norepinephrine (0.1 mumol/L) (49.2 +/- 18.2%, P < .01). In isolated vascular smooth muscle cells DHEAS reversibly inhibited KCl (30 mmol/L)-induced elevations of cytosolic free calcium to 69.8 +/- 8.4% and 43.8 +/- 7.4% of the control response at 5 x 10(-7) and 5 x 10(-6) mol/L, respectively (P < .05 at both doses). These results provide evidence of a direct vascular action of DHEAS, in doses reflecting circulating levels in vivo, and suggest the possibility that these effects are mediated by modulation of intracellular calcium metabolism. We hypothesize that physiologically, DHEAS may serve to buffer vascular responsiveness to a wide variety of depolarizing and constrictor hormonal stimuli.

Changes in alpha 1-adrenoceptor coupling to Ca2+ channels during development in rat heart.

It has been reported in the literature that alpha 1-adrenoceptor activation in adult rat heart does not cause an increase in Ca2+ current but involves a decrease in I(t). This may explain in part the positive inotropic effect of alpha 1-adrenoceptor activation. In this study, the effect of phenylephrine, an alpha-adrenergic agonist, on L-type Ca2+ channel current was compared in young and neonatal rat myocytes. In the presence of propranolol, phenylephrine increased the Ca2+ current (reversed by prazosin) in neonatal but not in young rat myocytes suggesting that the coupling of the alpha 1-adrenoceptor to Ca2+ channels may switch during development.

The effects of parathyroid hormone on L-type voltage-dependent calcium channel currents in vascular smooth muscle cells and ventricular myocytes are mediated by a cyclic AMP dependent mechanism.

The present study demonstrated that L channel currents were decreased in smooth muscle cells, and increased in ventricular myocytes by both bovine parathyroid hormone, (bPTH-(1-34)), and dibutyryl cyclic AMP (db-cAMP), using the whole cell version of the patch clamp technique with Ba2+ as the charge carrier. The effects of bPTH-(1-34) and db-cAMP on L channel currents were additive but not synergistic. Furthermore, the effects of bPTH-(1-34) on L channel currents in these 2 cell preparations were abolished in the presence of a cAMP antagonist. These results suggest that the effects of bPTH-(1-34) on L channel currents in vascular smooth muscle cells and ventricular myocytes are mediated by a cAMP-dependent mechanism.

Tetrandrine: a novel calcium channel antagonist inhibits type I calcium channels in neuroblastoma cells.

Tetrandrine, an alkaloid isolated from the Chinese herb, Radix stephaniae tetrandrae, has been used clinically as a hypotensive agent for a long time. Recently, several studies have demonstrated that tetrandrine behaves like a calcium entry blocker. In the present investigation, the whole cell version of the patch clamp technique was used to study the effect of tetrandrine on the type I (transient inward) calcium current in neuroblastoma cells. These results showed that tetrandrine inhibited the transient inward current, without affecting the channel kinetics. The effects of tetrandrine were dose-dependent and reversible but did not depend on the frequency of stimulation (use-dependence) or the membrane potential. These data clearly demonstrate that tetrandrine is a novel and potent antagonist of the transient inward current in neuroblastoma cells.

Production of polyclonal antisera to parathyroid hypertensive factor from spontaneously hypertensive rats.

OBJECTIVE: Parathyroid hypertensive factor (PHF) is a newly described hypertensive factor which may cause elevation of blood pressure in approximately 40% of North American essential hypertensive patients. PHF is also found in several animal models of hypertension, including spontaneously hypertensive rats (SHR), deoxycorticosterone acetate-salt hypertensive rats and salt-sensitive Dahl rats. The objective of the present study was to raise an antibody to PHF, and to use this antibody to study the effect of PHF in SHR. DESIGN: Plasma and parathyroid gland culture media collected from SHR were used in the present study as the antigen in the production and analysis of a polyclonal antiserum to PHF. METHODS: PHF is of low molecular weight (approximately 3000 daltons) and is sensitive to inactivation by trypsin. We used PHF partially purified from parathyroid gland culture media as the antigen to inoculate mice. The substance was bound to aminophenyl thioether paper discs to make it more antigenic. The discs were then emulsified in Freund's adjuvant (complete for first inoculation, incomplete for subsequent inoculations) for intraperitoneal implantation. Production of anti-PHF antisera was monitored by enzyme-linked immunosorbent assay. RESULTS: Antisera produced in mice reacted with purified PHF prepared from SHR plasma as well as with PHF prepared from parathyroid gland culture media. PHF treated with the PHF antiserum produced no characteristic hypertensive response in normotensive assay rats. The antisera did not crossreact with two forms of bovine parathyroid hormone, bPTH (1-84), bPTH (1-34) or with shorter parathyroid hormone fragments, or with any other vasoactive substance tested. Injection of an aliquot of the antiserum in anesthesized spontaneously hypertensive rats reduced mean arterial pressure to a normal range of approximately 110 mmHg. CONCLUSIONS: These results indicate that (1) polyclonal antisera to PHF can be raised in mice and (2) PHF may contribute significantly to the elevated blood pressure in SHR.

A new circulating hypertensive factor in the plasma of essential hypertensive subjects.

The pressor responses to dialyzed plasma extracts from normotensive (n = 15) and essential hypertensive (n = 14) human subjects were evaluated in anesthetized Sprague-Dawley rats. Hypertensive but not normotensive plasma raised mean arterial pressure (23.6 +/- 3.6 versus -0.5 +/- 2.5 mmHg, P less than 0.0001), and this effect was correlated significantly with its ability to stimulate 45Ca uptake in rat tail artery vascular smooth muscle (r = 0.883, P less than 0.002). These data suggest a humoral contribution to the pathophysiology of essential hypertension in at least some individuals. The time-course and molecular weight distribution of the dialyzed plasma suggest that this effect is not due to known vasopressor substances, but to a factor we tentatively term plasma hypertensive factor.

Parathyroid hypertensive factor-like activity in human essential hypertension: relationship to plasma renin activity and dietary salt sensitivity.

OBJECTIVE: To determine the clinical relevance of the newly described circulating pressor factor with parathyroid hypertensive factor (PHF)-like activity. DESIGN: Plasma samples were collected from 94 normotensive and 93 essential hypertensive subjects, the latter either previously defined by dietary salt sensitivity (n = 43), or prospectively studied on both low- (< 50 mmol/day) and high-salt (> 200 mmol/day) diets (n = 16). METHODS: Blood pressure, demographic factors, plasma renin activity (PRA), urinary electrolyte excretion and bioassayable PHF-like activity were determined in the fasted state on basal and altered dietary salt intakes. RESULTS: Among the normotensive subjects significantly higher PHF-like activity and reciprocally lower PRA values were observed in Black versus Caucasian subjects, particularly among females. In the hypertensive subjects PHF-like activity levels were significantly elevated in the low- (17.1 +/- 1.5 mmHg, n = 34) and normal- (6.7 +/- 1.8 mmHg, n = 36) but not in the high-renin subgroups compared with values in the normotensive subjects (1.6 +/- 1.1 mmHg). Similarly, PHF-like activity values were significantly higher in salt-sensitive than in salt-insensitive hypertensives. Prospectively, PHF-like activity rose significantly with salt loading (4.9 +/- 1.2 to 20.4 +/- 6.2 mmHg) and was positively related (r = 0.648, P < 0.001) to the pressor response to salt. CONCLUSIONS: Elevated levels of PHF-like activity are characteristic of the low-renin or salt-sensitive state, or both, and may contribute to the hypertensive process. Elevated PHF-like activity levels found in normotensive subjects may presage the development of low-renin, salt-sensitive hypertension.

Parathyroid origin of a new hypertensive factor.

Many physiological abnormalities have been described in essential hypertension, yet the cause of this condition remains unknown. Included among the reported abnormalities are alterations in serum and tissue calcium levels, abnormalities in calcium regulating hormones, and the involvement of the parathyroid gland in some forms of hypertension. In the current study, the authors review evidence suggesting that a newly described hypertensive factor may explain a number of these abnormalities. This factor was first described in spontaneously hypertensive rat (SHR) plasma and is characterized by its ability to raise blood pressure in a delayed manner in normotensive rats, as well as by its ability to increase calcium uptake in vascular smooth muscle. The factor seems to be produced by the parathyroid gland, yet it is distinct from parathyroid hormone. Histological studies suggest that the factor may be produced by a specific cell type in the parathyroid glands. Given the parathyroid gland dependency of this factor, the authors have tentatively named it "parathyroid hypertensive factor," or "PHF."

Control of calcium channels in neuroblastoma cells (N1E-115).

Neuroblastoma cells (N1E-115) were used as models of transient (T) and long-lasting (L) Ca++ channels. The whole cell version of the patch clamp technique was used to measure inward Ca++ currents, and the fluorescent indicator, Fura-2, was used to measure changes in intracellular Ca++. Cells were cultured and selected during recording so that predominantly T or L channel currents were measured. T channel currents did not respond to dihydropyridine or parathyroid hormone, whereas L channel currents did. BAY-K-8644 increased and nifedipine decreased L channel currents. After a 15 mM KCl challenge, cells with predominantly T channels responded with a transient change in intracellular Ca++, while cells with predominantly L channels showed a sustained response. PTH inhibited the increase in intracellular Ca++ in cells with L channels, but not in those with T channels. PTH may be an example of an endogenous calcium channel blocker, at least in neuroblastoma cells.