Presence of atrial natriuretic factor and cyclic guanosine monophosphate in saliva. Comparison of plasma and salivary concentrations during a head-down tilt

Natriuretic peptide system expression in murine and human submandibular salivary glands: a study of the spatial localisation of ANB, BNP, CNP and their receptors

The natriuretic peptide (NP) system comprises of three ligands, the Atrial Natriuretic Peptide (ANP), Brain Natriuretic peptide (BNP) and C-type Natriuretic peptide (CNP), and three natriuretic peptide receptors, NPRA, NPRB and NPRC. Here we present a comprehensive study of the natriuretic peptide system in healthy murine and human submandibular salivary glands (SMGs). We show CNP is the dominant NP in mouse and human SMG and is expressed together with NP receptors in ducts, autonomic nerves and the microvasculature of the gland, suggesting CNP autocrine signalling may take place in some of these glandular structures. These data suggest the NP system may control salivary gland function during homeostasis through the regulation of electrolyte re-absorption, neural stimulation and/or blood vessel wall contraction/relaxation. We also show abnormal expression of NPRA in the stroma of a subset of human SMGs resected from patients diagnosed with oral squamous cell carcinoma (OSCC) of non-salivary gland origin. This finding warrants further research to investigate a possible correlation between early OSCC invasion and NPRA overexpression.

Potential and Limitations of Atrial Natriuretic Peptide as Biomarker in Pediatric Heart Failure-A Comparative Review

Although B-type Natriuretic Peptide (BNP), N-terminal-proBNP (NT-proBNP), and mid-regional-proANP (MR-proANP) are included in current guidelines on heart failure in adults, no guideline considering these biomarkers in pediatric heart failure is available. A new drug class of neprilysin inhibitors as fixed-dose combination (Sacubitril/valsartan) has been introduced and is currently being investigated in children suffering from heart failure. Atrial Natriuretic Peptide (ANP) is discussed as a more useful alternative to BNP because it may grants better insights into the effects of this treatment. Thus, this review aimed to provide an overview of the current knowledge concerning ANP in pediatric heart failure and compares its suitability regarding diagnosis and prognosis of heart failure. A literature search using PubMed resulted in 147 publications of which 22 studies were classified as relevant. The review presents available ANP, NT-proANP, and MR-proANP level data in children (0-18 years). Summarizing, ANP shows only minor differences as marker for diagnosing and monitoring pediatric heart failure if compared to BNP. Due to its fast release, ANP offers the advantage of displaying rapid changes during therapy or operation. ANP is -like the other natriuretic peptides- influenced by age, presenting with the highest levels in very young infants. ANP also correlates with atrial pressure and volume overload in children. In addition, ANP determination in saliva appears to be a promising alternative to blood sampling. Similarly to NT-proBNP, NT-proANP, and MR-proANP offer better stability but only few data has been published in children and thus their potential is only presumable so far.

cAMP and cGMP in human parotid saliva: relationships to taste and smell dysfunction, gender, and age

Among the chemical moieties present in human parotid saliva, some, such as gustin or carbonic anhydrase VI, have been useful to distinguish patients with taste and smell dysfunction from normal subjects. To continue these studies we compared levels of salivary cAMP and cGMP in patients with taste and smell dysfunction with those in normal subjects. We were also interested in exploring physiological characteristics of salivary cAMP and cGMP including changes with gender and age because previous studies had not clearly defined these issues. To perform these studies parotid saliva was collected from 61 normal volunteers and 253 patients with taste and smell dysfunction. cAMP and cGMP were measured by a spectrophotometric 96 plate ELISA technique; parotid salivary protein and flow rate were also measured. Both cAMP and cGMP were found in saliva of normal subjects and patients in the detection range of the assay used. In patients mean concentrations of both cAMP and cGMP were lower than in normal subjects; for cAMP levels were lower among both men and women patients. cAMP was 7 to 10 times higher than cGMP in both normal subjects and patients. Concentrations of cAMP were consistently higher in normal women than in normal men. cAMP levels were generally lower and cGMP levels were generally higher than in previously reported studies. There was a complex pattern of change for both cAMP and cGMP with age with concentrations increasing to about age 50, then decreasing, then increasing again at age >70 years.

Better preservation of endothelial function and decreased activation of the fetal renin-angiotensin pathway with the use of pulsatile flow during experimental fetal bypass

OBJECTIVE

Pulsatile flow was shown to overcome the progressive rise in peripheral and placental vascular resistances observed during steady-flow bypass, this rise being counteracted by inhibition of nitric oxide synthase. This study quantifies the release of endothelial vasoactive substances during a 60-minute in utero model of fetal bypass.

METHODS

Fetuses were randomly allocated into 1 of 2 groups (steady flow, n = 8, or pulsatile flow, n = 13) and subjected to bypass through central cannulation and perfusion with either a centrifugal or pulsatile (125 beats x min(-1)) blood pump.

RESULTS

Lactate concentration was high, starting at fetal exteriorization and increasing during fetal preparation in the 2 groups. Once bypass was established, the rise was significant only in the steady-flow group. Plasma nitric oxide metabolites, similar before bypass, reached higher levels during pulsatile flow at the end of bypass (99+/-9 vs. 82+/-23 micromol x L(-1); P =.037). Levels of urinary nitric oxide metabolites were significantly higher in the pulsatile-flow than in the steady-flow group (764+/-143 vs. 508+/-240 micromol x L(-1); P =.005). Plasma cyclic guanosine monophosphate levels increased after 30 minutes of bypass in the pulsatile-flow group (25+/-18 vs. 12+/-8 pmol x mL(-1); P =.004), and urinary cyclic guanosine monophosphate excretion was higher in the pulsatile-flow group (517+/-450 vs. 118+/-78 pmol x mL(-1); P =.024). Plasma endothelin-1 levels increased in the 2 groups and were higher in the steady-flow group at 30 minutes (27+/-5 vs. 23+/-2 pg x mL(-1); P =.04) and 60 minutes of bypass (39+/-7 vs 32 +/- 6 pg x mL(-1); P =.04). Plasma renin concentration increased significantly during bypass only in the steady-flow group (26+/-10 vs. 57+/-42 in ng A1 x mL(-1) x h(-1); P =.04).

CONCLUSIONS

Improved placental and peripheral perfusion during fetal pulsatile-flow bypass may be mediated by preservation of fetal/maternal endothelial nitric oxide biosynthetic mechanisms and/or decreased activation of the fetal renin-angiotensin pathway.

Nocturnal increase in plasma cGMP levels in humans

The circadian dynamics of responses to cyclic guanosine 3',5'-monophosphate (cGMP) in in vitro experiments and the stimulating effects of the pineal hormone melatonin on cGMP levels both in vitro and in vivo provoked an investigation into the diurnal pattern of occurrence of this second messenger in human plasma and its correlation with plasma melatonin levels. Plasma cGMP levels were measured in 9 normal human subjects who were over 50 years of age. Samples were obtained hourly through a 20-h period (11 a.m. to 7 a.m.) that included the subjects' habitual hours of nocturnal sleep; physical activity was kept to a minimum during the daylight hours. The area under the time-plasma cGMP concentration curve showed a significant increase during the period of nocturnal sleep compared to that observed during the period of daytime wakefulness. The individual temporal pattern of the nocturnal rise in plasma cGMP differed among the subjects; however, the initial increase typically was observed soon after bedtime. No significant correlation was observed between individual nocturnal plasma melatonin levels and cGMP levels.

Localization of atrial natriuretic peptide receptors in the rat tongue and hard palate

Atrial natriuretic peptide (ANP) receptors were characterized in rat oral mucosa using quantitative in vitro autoradiography and activation of particulate guanylyl cyclase (GC) by natriuretic peptides. Competition-binding analysis performed by quantitative in vitro autoradiography demonstrated specific [125I]rANP(1-28) binding sites in the tongue and hard palate. The precise location of this binding was revealed on the basal and parabasal cells of the epithelia by microautoradiography. The dissociation constant (Kd) and maximal binding capacity (Bmax) of these sites were 3.34+/-1.35 nM and 2.71+/-2.21 fmol/mm2 on the epithelium of the tongue, and 4.09+/-1.52 nM and 3.45+/-3.01 fmol/mm2 on the epithelium of the hard palate, respectively. Receptor subtypes were characterized by competition with des [Gln18, Ser19, Gly20, Leu21, Gly22] ANP(4-23) (C-ANP), a specific ligand for the clearance receptor (NPR-C). These binding sites were displaced by C-ANP with inhibition constant (Ki) of 8.96+/-3.18 nM and Bmax of 2.89+/-2.45 fmol/mm2 on the epithelium of the tongue, and Ki of 9.12+/-2.71 nM and Bmax of 3.08+/-2.94 fmol/mm2 on the epithelium of the hard palate, respectively. Production of cyclic GMP by particulate GC in the epithelial membranes of the tongue and hard palate was stimulated by rANP(1-28), porcine brain natriuretic peptide (BNP)(1-26), and C-type natriuretic peptide (CNP)(1-22) in a dose-dependent manner. These results indicate that ANP-binding sites in the epithelium of the tongue and hard palate are mainly clearance receptors (NPR-C) but biological receptors (NPR-A and/or NPR-B) with GC activity are also present, and suggest that ANP may have a role in the proliferation of the oral epithelial cells, especially in the tongue and hard palate.

Blood volume regulating hormones, fluid and electrolyte modifications during 21 and 198-day space flights (Altair-MIR 1993)

During the Altair MIR '93 mission we studied several parameters involved in blood volume regulation. The experiment was done on two cosmonauts before (B-60, B-30), during (D6, D12, D18 for French and D7, D12, D17 for Russian) and after the flight (R+1, R+3 and R+7). Space flight durations were different for two cosmonauts: for the Russian the flight duration was 198 days and for the French 21 days. On board the MIR station only urinary (volume and electrolytes, atrial natriuretic peptide (ANP), cyclic guanosine monophosphate (cGMP) and catecholamines) and salivary (cGMP and cortisol) samples were collected, centrifuged and stored in freezer. Lithium was used as a tracer to know exactly the 24 h urine output (CNES urine collection Kit). Before and after flight, blood was drawn with an epicite needle and vacutainer system for hormonal assays (renin, antidiuretic hormone, cGMP, ANP and aldosterone) in two positions: after 30 min rest in upright seated position and after 90 min of supine position. Salivary samples were collected simultaneously. During flight a decrease of diuresis and ANP and an increase of osmolality were found. No modifications of hematocrit, but an increase of salivary cGMP and cortisol were also observed. The decrease of urinary ANP is in favor of hypovolemia as described in previous flights. The postflight examinations revealed changes in fluid-electrolyte metabolism which indicate a hypohydration status and a stimulation of hormonal system responsible for water and electrolyte retention in order to readapt to the normal gravity.