A monoclonal antibody against N-terminus of alpha-atrial natriuretic polypeptide (alpha-ANP): a useful tool for preferential detection of naturally circulating ANP

A monoclonal antibody directed against the N-terminus of alpha-atrial natriuretic polypeptide (alpha-ANP), named KY-ANP-II, was produced by fusion of a non-producing mouse myeloma cell line, X63-Ag8.653, with spleen cells from a BALB/c mouse immunized with synthetic alpha-human ANP (alpha-hANP) conjugated to bovine thyroglobulin. The obtained antibody showed a high affinity for alpha-hANP with a Ka of 6.6 X 10(10) M-1. With this monoclonal antibody, a specific radioimmunoassay for alpha-hANP was established. The minimal detectable level of alpha-hANP in this radioimmunoassay was 0.8 fmol (2.5 pg)/tube, and IC50 was 8 fmol (25 pg)/tube. The radioimmunoassay recognized alpha-rat ANP on an equimolar basis, whereas there was no detectable cross-reactivity with alpha-ANP [4-28] or alpha-ANP [5-28]. Thus, the monoclonal antibody can detect a hormonal form of ANP, alpha-ANP, but not neuropeptide forms of ANP, alpha-ANP [4-28] and alpha-ANP [5-28]. These results indicate that KY-ANP-II becomes a useful tool for preferential detection of a circulating form of ANP and for investigation of the physiological and pathophysiological significance of ANP as a hormone.

Central interaction of the brain atrial natriuretic polypeptide (ANP) system and the brain renin-angiotensin system in ANP secretion from heart--evidence for possible brain-heart axis

To elucidate the involvement of the brain renin-angiotensin system and the brain atrial natriuretic polypeptide (ANP) system in the regulation of ANP secretion from the heart, the effects of intracerebroventricular administration of angiotensin II and ANP on the plasma ANP level were examined in conscious unrestrained rats. The intracerebroventricular administration of angiotensin II at doses of 100 ng and 1 microgram significantly enhanced ANP secretion induced by volume-loading with 3-mL saline infusion (peak values of the plasma ANP level: control, 220 +/- 57 pg/mL; 100 ng angiotensin II, 1110 +/- 320 pg/mL, p less than 0.01; 1 microgram angiotensin II, 1055 +/- 60 pg/mL, p less than 0.01). The intracerebroventricular injection of angiotensin II at the same doses alone had no significant effect on the basal plasma ANP level. The enhancing effect of central angiotensin II on ANP secretion induced by volume-loading was significantly attenuated by pretreatment with the intravenous administration of the V1-receptor antagonist of vasopressin or with the intracerebroventricular administration of phentolamine. The intracerebroventricular administration of alpha-rANP(4-28) (5 micrograms) had no significant influence on the basal plasma ANP level; however, it significantly attenuated central angiotensin II potentiating effect of volume-loading induced ANP secretion. These results indicate that the brain renin-angiotensin system regulates ANP secretion via the stimulation of vasopressin secretion and (or) via the activation of the central alpha-adrenergic neural pathway, and that the brain ANP system interacts with the brain renin-angiotensin system in the central modulation of ANP secretion from the heart.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory action of leumorphin on vasopressin secretion in conscious rats

To elucidate the role of leumorphin, a kappa-agonist derived from proenkephalin-B (neoendorphin/dynorphin precursor), in the control of arginine vasopressin (AVP) secretion, we examined the effects of intracerebroventricular (icv) administration of leumorphin on AVP secretion under basal and stimulated conditions in conscious unrestrained rats. Intracerebroventricular injection of leumorphin (60 or 600 pmol) significantly inhibited basal AVP secretion. In 72-h water-deprived rats, icv injection of leumorphin (60 or 600 pmol) also suppressed AVP secretion in a dose-dependent manner. The AVP response induced by icv injection of angiotensin II (100 pmol) was significantly decreased by the simultaneous icv injection of leumorphin (6-600 pmol) in a dose-dependent manner. Intracerebroventricular administration of leumorphin (600 pmol) also reduced the AVP secretion stimulated by icv injection of carbachol (50 pmol). Intravenous pretreatment with naloxone (0.5 mg/kg BW) diminished the inhibitory action of leumorphin (60 pmol) on AVP secretion. However, no effect on AVP secretion was observed after iv injection of leumorphin (600 pmol). These results indicate that leumorphin possesses a potent inhibitory effect on AVP secretion, suggesting its important role in the regulation of AVP secretion in the brain.

Subcellular distribution and isoelectric heterogeneity of the substrate for ADP-ribosyl transferase from Clostridium botulinum

When the homogenate of bovine adrenal gland was subjected to subcellular fractionation, an Mr 21,000 substrate for botulinum ADP-ribosyl transferase was found not only in the membrane fractions but also in the cytosol; the amounts in the 10,000 x g precipitates and the 100,000 x g supernatant were about 21 and 56% of the total amount, respectively. Each fraction gave a single ADP-ribosylated protein band on SDS-polyacrylamide gel electrophoresis, but yielded on isoelectric focusing at least three bands between pH 5.5 and 6.0, suggesting the presence of multiple forms of the substrate of a similar molecular weight but different isoelectric points. ADP-ribosylated protein bands from the membrane and cytosol overlapped each other on both electrophoreses. After ammonium sulfate fractionation, the substrate from the cytosol showed requirement of divalent cations or guanine nucleotides for the reaction. Among cations tested, calcium, magnesium and manganese stimulated, whereas cadmium and lanthanum inhibited the reaction. Guanine nucleotides such as GTP, GDP and GTP-gamma-S also stimulated the substrate activity in the cytosol as that in the membrane fraction. However, no additive effects were observed when the nucleotides and cations were added together.

Secretion of N-terminal fragment of gamma-human atrial natriuretic polypeptide

To elucidate the posttranslational processing of gamma-human atrial natriuretic polypeptide (human atrial natriuretic factor-[1-126]), which is a prohormone of alpha-human atrial natriuretic polypeptide (human atrial natriuretic factor-[99-126]), and the secretion of gamma-human atrial natriuretic polypeptide-derived peptides from the heart, we established a radioimmunoassay specific for the N-terminal sequence of gamma-human atrial natriuretic polypeptide, gamma-human atrial natriuretic polypeptide-(1-25), as well as a radioimmunoassay for alpha-human atrial natriuretic polypeptide. With the aid of the radioimmunoassays for gamma-human atrial natriuretic polypeptide-(1-25) and for alpha-human atrial natriuretic polypeptide, we detected 290 +/- 35.6 pg/ml of gamma-human atrial natriuretic polypeptide-(1-25)-like immunoreactivity in plasma from healthy humans, while the simultaneously determined plasma alpha-human atrial natriuretic polypeptide-like immunoreactivity level was 20.9 +/- 2.8 pg/ml. Correlation between the two values was significant. High performance gel permeation chromatographic analysis revealed that the plasma gamma-human atrial natriuretic polypeptide-(1-25)-like immunoreactivity was composed of a component (molecular weight, 10,000) without alpha-human atrial natriuretic polypeptide-like immunoreactivity, while the plasma alpha-human atrial natriuretic polypeptide-like immunoreactivity was composed of alpha-human atrial natriuretic polypeptide with a molecular weight of 3000. In patients with heart diseases, the plasma gamma-human atrial natriuretic polypeptide-(1-25)-like immunoreactivity level showed a concomitant and graded increase, with the plasma alpha-human atrial natriuretic polypeptide-like immunoreactivity level in agreement with the severity of the disease. There were significant positive correlations between the two immunoreactivity levels and right or left atrial pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain renin-angiotensin. Central control of secretion of atrial natriuretic factor from the heart

To elucidate the modulatory role of the brain renin-angiotensin system in the regulation of the secretion of atrial natriuretic factor (ANF) from the heart, the effects of intracerebroventricular administration of angiotensin II on the plasma ANF level were examined in conscious unrestrained rats. Administration of angiotensin II in doses of 100 ng and 1 microgram significantly enhanced ANF secretion induced by volume loading with infusion of 3 ml of saline (peak values of the plasma ANF level: control, 220 +/- 57 pg/ml; angiotensin II 100 ng, 1110 +/- 320 pg/ml, p less than 0.01; angiotensin II 1 microgram, 1055 +/- 60 pg/ml, p less than 0.01). Injection of angiotensin II alone had no significant effect on the basal plasma ANF level. Central angiotensin II-induced ANF secretion was significantly attenuated by pretreatment with intravenous administration of the V1-receptor antagonist of vasopressin or intracerebroventricular administration of phentolamine. These results indicate that the brain renin-angiotensin system modulates ANF secretion in response to volume loading through the stimulation of vasopressin secretion or the activation of the central alpha-adrenergic neural pathway.

Implication of leumorphin in inhibitory control of vasopressin secretion in conscious rats

The effects of leumorphin, a kappa-agonist derived from proenkephalin B (neoendorphin and dynorphin precursor), on vasopressin secretion were studied under basal and stimulated conditions in conscious, unrestrained rats. Intracerebroventricular injection of leumorphin (60 or 600 pmol) significantly inhibited basal vasopressin secretion. The vasopressin response induced by intracerebroventricular injection of angiotensin II (100 pmol) was significantly suppressed, in a dose-dependent fashion, by the simultaneous intracerebroventricular injection of leumorphin (6, 60, or 600 pmol). Intravenous pretreatment with naloxone (0.5 mg/kg body weight) diminished the inhibitory action of leumorphin (60 pmol) on vasopressin secretion. Moreover, naloxone (0.5 mg/kg body weight) prolonged the vasopressin secretion induced by intracerebroventricular injection of angiotensin II (100 pmol). These results indicate that leumorphin possesses a potent inhibitory effect on vasopressin secretion and that, alone or in combination with other endogenous opioid peptides, it plays an important role in the control of vasopressin secretion.

Atrial natriuretic factor in essential hypertension and adrenal disorders

Patients with untreated essential hypertension had significantly higher plasma atrial natriuretic factor (ANF) levels (92.9 +/- 12.9 pg/ml, mean +/- SE) than those of age-matched controls (37.8 +/- 6.0 pg/ml; p less than 0.01). Plasma ANF levels in essential hypertensive patients showed a significant positive correlation with mean arterial pressure (MAP; r = 0.46, p less than 0.05) and an inverse correlation with plasma renin activity (PRA; r = -0.43, p less than 0.05). Plasma ANF levels after medication showed significant correlation with the decrease in MAP (r = 0.565, p less than 0.05). Patients with primary aldosteronism had significantly higher plasma ANF levels (122.4 +/- 30.2 pg/ml, n = 8) than those of controls (p less than 0.05). The levels returned to normal after extirpation of adrenal tumors. The response of plasma ANF levels in patients with primary aldosteronism to volume expansion with infusion of 2 L of physiological saline in 2 hours was greater than in controls. Such exaggerated response disappeared after surgical treatment. Infusion of angiotensin II (Ang II; 20 ng/kg/min) or norepinephrine (200 ng/kg/min) for 30 minutes to normal volunteers (n = 5) resulted in a rise in MAP (24.9 +/- 3.3 and 15.8 +/- 4.4 mm Hg, respectively) and a twofold increase in plasma ANF level. Infusion of the Ang II antagonist [Sar1, Ile8]Ang II (600 ng/kg/min) for 30 minutes, resulted in a rise in MAP (18.8 +/- 2.1 mm Hg) and more than a twofold increase in plasma ANF level in patients with essential hypertension (n = 6).(ABSTRACT TRUNCATED AT 250 WORDS)

Augmented synthesis of beta-human atrial natriuretic polypeptide in human failing hearts

To elucidate the synthesis of atrial natriuretic polypeptide (ANP) in the failing heart, eighteen human right auricles obtained at cardiovascular surgery were studied. The concentration of alpha-human ANP-like immunoreactivity (alpha-hANP-LI) in human right auricles ranged from 13.8 to 593.5 micrograms/g, and the tissue alpha-hANP-LI concentration in severe congestive heart failure (CHF) (New York Heart Association (NYHA) functional class III or IV) was much higher than those in mild CHF of NYHA class I and class II. The alpha-hANP-LI in the human auricle consisted of 3 major components of ANP, gamma-human ANP (gamma-hANP), beta-human ANP (beta-hANP) and alpha-human ANP (alpha-hANP). The predominant component of alpha-hANP-LI was gamma-hANP in the mild CHF, whereas beta-hANP and/or alpha-hANP were prevailing in the severe CHF and, especially, beta-hANP was markedly increased in human failing hearts.

Opioid modulation of vasopressin secretion in conscious rats

To clarify the role of endogenous opioid peptides in the control of vasopressin (AVP) secretion, the effects of an endogenous kappa-agonist, leumorphin, derived from proenkephalin B and an opioid antagonist, naloxone, on AVP secretion were examined in conscious and freely moving rats. Intraperitoneal injection of nicotine markedly increased AVP secretion in rats. The nicotine-induced AVP secretion was significantly suppressed by intracerebroventricular (i.c.v.) pretreatment with leumorphin. Intravenous injection of naloxone significantly increased the basal AVP level and carbachol-induced AVP secretion. These results indicate that endogenous opioid peptides have an inhibitory effect on AVP secretion in rats.

Pyrethroids and the striatal dopaminergic system in vivo

1. Type I (permethrin and allethrin) or type II (cypermethrin and fenvalerate) pyrethroids caused 23-37% increases in the striatal content of the dopamine metabolite 3,4-dihydroxyphenylacetic acid (DOPAC). 2. Toxicity symptoms and increases in DOPAC were associated with higher brain concentrations for type I (2.6-5.8 micrograms/gm) than type II pyrethroids (0.4-0.6 micrograms/gm). 3. No specific difference in the interaction between type I and II pyrethroids and the striatal dopaminergic system were recognized.

Simultaneous measurement of atrial natriuretic polypeptide (ANP) messenger RNA and ANP in rat heart--evidence for a preferentially increased synthesis and secretion of ANP in left atrium of spontaneously hypertensive rats (SHR)

Tissue levels of atrial natriuretic polypeptide (ANP) messenger RNA (ANPmRNA) and ANP in the rat heart were measured simultaneously. In Wistar rats, ANPmRNA of the same size (approximately 0.95 kbp) was detected in all four chambers of the rat heart. The ANPmRNA level was the highest in the right atrium, and the left atrial level was slightly lower than the right atrial level. Ventricular levels were more than two orders of magnitude lower than atrial levels. Tissue ANP concentrations of four chambers were roughly parallel to ANPmRNA levels. In spontaneously hypertensive rats (SHR) with the elevated plasma ANP level, the ANPmRNA level in the left atrium was substantially increased. The left/right ratio of atrial ANPmRNA level in SHR (150%) was higher than that in control Wistar Kyoto rats (WKY) (90%). In contrast, the left/right ratio of atrial ANP concentration was decreased in SHR (44%) compared with that in WKY (84%). The ratio of ANP to ANPmRNA levels in the left atrium of SHR was about three times smaller than that in the right atrium of SHR, and those in bilateral atria of WKY. These results indicate that the biosynthesis and secretion of ANP from the left atrium is preferentially increased in SHR. Thus, simultaneous determination of ANPmRNA and ANP levels is a refined strategy of investigation for the biosynthesis, storage and secretion of ANP.

Atrial natriuretic polypeptide (ANP) in human ventricle. Increased gene expression of ANP in dilated cardiomyopathy

Tissue levels of atrial natriuretic polypeptide (ANP) messenger RNA (ANPmRNA) and ANP in the human atrium and ventricle were measured simultaneously by the blot hybridization technique and the specific radioimmunoassay for ANP. Hearts were obtained from two patients without cardiac complications and from a patient with dilated cardiomyopathy (DCM) at autopsy. Total RNA extracted from ventricles contained a hybridizing RNA band of the same size as atrial ANPmRNA in both control and DCM hearts. The ANPmRNA level in the control ventricle was 0.2% of that in the atrium. The ANPmRNA level in the DCM ventricle increased to about 7% of that in the corresponding atrium and was approximately 40 times higher than that in the control ventricle, although the ANPmRNA level in the DCM atrium was comparable to that in the control atrium. The total content of ANPmRNA in the DCM ventricle reached about 30% of that in the corresponding atrium and was much the same as that in the control atrium. The ANP level in the DCM ventricle was approximately 1.0 microgram/g and much higher than that in the control ventricle (0.02 microgram/g).

Central actions of atrial natriuretic polypeptides in spontaneously hypertensive and normotensive rats

The effects of intracerebroventricular (i.c.v.) administration of ANP on blood pressure and intakes of water and salt were examined, using conscious, unrestrained normotensive Wistar rats and spontaneously hypertensive rats (SHR). In normotensive rats, i.c.v. administration of alpha-rat ANP (alpha-rANP), alpha-human ANP (alpha-hANP), alpha-rANP (4-28) and alpha-rANP (5-28) at the dose of 1.5 nmol significantly attenuated water intake induced by i.c.v. injection of 0.1 nmol of angiotensin II (AII). Centrally administered alpha-hANP (5 micrograms) also attenuated AII-induced pressor response. Centrally injected alpha-hANP (1 microgram) produced a greater reduction of water intake after 24-hour water deprivation in SHR compared to control Wistar Kyoto rats (WKY). Central infusion of alpha-hANP for 1 week also reduced the salt appetite of SHR, as shown by two bottle preference test with 0.3 M NaCl solution and tap water, while it had no effect on drinking behavior of WKY. These results suggest the central antagonistic relationship of the ANP and renin-angiotensin systems and the possible involvement of brain ANP in the pathophysiology of genetically hypertensive rats.

Atrial natriuretic polypeptide during exercise in healthy man

The plasma concentration of atrial natriuretic polypeptide was measured in eight healthy men during two grades of exercise performed in the supine position on a bicycle ergometer. The plasma concentration of atrial natriuretic polypeptide slightly increased during the first exercise test with 20% of the maximal oxygen uptake and it approximately doubled during the second exercise with 40% of the maximal oxygen uptake (from 15.5 +/- 5.5 (mean +/- SD) pmol/l to 31.8 +/- 10.7 pmol/l). The increase in the plasma level of atrial natriuretic polypeptide in the second exercise was significantly greater than that in the first one. The plasma norepinephrine level and plasma renin activity showed significant increases during the second exercise test. Heart rate and systolic blood pressure also increased in response to the graded exercise. The increase in the plasma concentration of atrial natriuretic polypeptide during exercise was significantly correlated with the increase in heart rate, systolic blood pressure, and the plasma norepinephrine concentration (r = 0.75, r = 0.71 and r = 0.51, respectively). These results indicate that the plasma concentration of atrial natriuretic polypeptide increases in response to the intensity of a workload, and suggest that exercise is a useful test to evaluate the releasing function of atrial natriuretic polypeptide in the heart.

Secretory form of atrial natriuretic polypeptide as cardiac hormone in humans and rats

To elucidate the secretory form of atrial natriuretic polypeptide from the atrium, the molecular form of atrial natriuretic polypeptide in the perfusate from the isolated beating rat heart and in plasma taken at the coronary sinus of 10 patients during cardiac catheterization has been investigated using high performance gel permeation chromatography and reverse phase high performance liquid chromatography coupled with radioimmunoassay for atrial natriuretic polypeptide. Atrial natriuretic polypeptide in the perfusate from the rat heart showed a single peak eluting at the position of a low molecular weight form of atrial natriuretic polypeptide, without any detectable amounts of atrial natriuretic polypeptide with high molecular weights. The major component of atrial natriuretic polypeptide in the rat heart perfusate co-migrated with rat alpha-atrial natriuretic polypeptide in reverse phase high performance liquid chromatography. In 9 out of 10 patients atrial natriuretic polypeptide in plasma taken at the coronary sinus revealed a single peak of atrial natriuretic polypeptide emerging at the position of human alpha-atrial natriuretic polypeptide in gel filtration. Only one plasma sample had a small quantity of high molecular weight forms with the predominant low molecular weight form of atrial natriuretic polypeptide. The major component of atrial natriuretic polypeptide in the plasma extract from the coronary sinus was identified with human alpha-atrial natriuretic polypeptide. These results indicate that alpha-ANP, a 28-amino acid polypeptide, is secreted as a cardiac hormone into the coronary blood stream from the atrium.

Ontogeny of atrial natriuretic polypeptide in the human heart

To elucidate the developmental changes of atrial natriuretic polypeptide in the human heart, we studied alpha-human atrial natriuretic polypeptide (alpha-hANP)-like immunoreactivity (alpha-hANP-LI) in the extracts from the hearts of three foetuses of 10, 14 and 22 weeks' gestation, a 1-day-old premature infant of 33 weeks' gestation, and two adults, alpha-hANP-LI levels in the atria of the three foetuses of 10, 14 and 22 weeks' gestation and the premature infant (31.4, 12.2, 9.25 and 15.3 nmol/g, respectively) were comparable to those in two adult atria (16.9 and 13.6 nmol/g). The ventricles also contained alpha-hANP-LI (0.763----0.0818 nmol/g with descending values with increasing gestational age) in the three foetuses and the premature infant although it was undetectable (less than 0.0162 nmol/g) in two adult ventricles. The highest alpha-hANP-LI concentration was observed in the auricles in all the hearts except in the premature infant. The concentration in the right auricle was higher than in the left during foetal life, whereas that in the left was the higher one after birth. High performance gel permeation chromatography coupled with radioimmunoassay revealed that alpha-hANP-LI in the atria and apexes of the foetuses and the premature infant consisted of gamma-hANP, beta-hANP and alpha-hANP, with gamma-hANP being the predominant form. Essentially similar gel filtration patterns were observed in the two adult atria. These results indicate that: ANP appears in human heart tissue early in foetal life; cardiac ventricles also contain ANP in the foetus, and there is probably no difference in posttranslational processing of the precursor molecule in foetal and adult hearts.

Atrial natriuretic polypeptide in spinal cord and autonomic ganglia

Using a radioimmunoassay for alpha-rat atrial natriuretic polypeptide (alpha-rANP), tissue levels of alpha-rANP-like immunoreactivity (-LI) in the rat spinal cord and autonomic ganglia were investigated. The alpha-rANP-LI level was higher in the more caudal parts of the spinal cord and the highest in the sacral spinal cord. alpha-rANP-LI was also detected in the superior cervical and coeliac ganglia. Gel permeation chromatographic analysis showed that the major peak of alpha-rANP-LI in the spinal cord was a low molecular weight form co-eluted with synthetic alpha-rANP. Reverse-phase high performance liquid chromatographic analysis revealed that alpha-rANP-LI with a low molecular weight in the spinal cord consisted of several components, two major components of which co-migrated with synthetic alpha-rANP (4-28) and alpha-rANP (5-28), whereas little immunoreactivity was eluted at the position of alpha-rANP. These findings suggest the involvement of ANP in the function of the spinal cord and autonomic nervous system.

Modulatory role of vasopressin in secretion of atrial natriuretic polypeptide in conscious rats

To investigate whether vasopressin is involved in the secretory mechanism of atrial natriuretic polypeptide (ANP), effects of arginine-vasopressin (AVP) administered iv on plasma ANP levels were studied in conscious, unrestrained rats. The administration of 100 ng and 1 microgram of AVP caused a dose-dependent increase of the plasma ANP level, which was blocked by a V1-receptor antagonist of AVP, and was attenuated by 5 ml blood volume reduction before the stimulation. The injection of less than 10 ng of AVP induced no significant effects on ANP secretion. However, the administration of 5 ng of AVP significantly enhanced ANP secretion induced by intravascular volume expansion with 3 ml saline infusion. These results suggest the possible physiological significance of AVP as a modulator rather than a direct stimulator of ANP secretion from the heart.

Conversion of beta-human atrial natriuretic polypeptide into alpha-human atrial natriuretic polypeptide in human plasma in vitro

Using synthetic beta-human atrial natriuretic polypeptide (beta-hANP), an antiparallel dimer of alpha-hANP, and radioimmunoassay (RIA) for alpha-ANP which also detects beta-hANP, we investigated the disappearance profile and the change in the molecular form of exogenously added beta-hANP in human plasma in vitro, compared with those of alpha-hANP. The ANP-like immunoreactivity (ANP-LI) level in beta-hANP-added human plasma exhibited slower disappearance than that in alpha-hANP-added plasma during the incubation at 37 degrees C. High performance-gel permeation chromatography and reverse phase-high performance liquid chromatography coupled with RIA revealed that beta-hANP (6K) was converted into a smaller peptide with an approximate molecular weight of 3K corresponding to alpha-hANP during the incubation. Amino acid analysis and amino-terminal sequencing confirmed that the converted peptide from beta-hANP in human plasma is authentic alpha-hANP. The demonstrated conversion of beta-hANP into alpha-hANP in human plasma could be relevant to the in vivo natriuretic and diuretic actions with slower onset and longer duration of this unique peptide.

Atrial natriuretic polypeptides: structure-activity relationship in the central action--a comparison of their antidipsogenic actions

The structure-activity relationship of atrial natriuretic polypeptides (ANPs) in the central action was investigated by examining the suppressive effects of the intracerebroventricular (i.c.v.) administration of ANPs on water intake induced by the i.c.v. injection of angiotensin II (AII) (0.1 nmol) in rats. alpha-Rat ANP (alpha-rANP), alpha-human ANP, alpha-rANP4-28 and alpha-rANP5-28 at a dose of 1.5 nmol exerted equipotent antidipsogenic actions, while alpha-rANP7-23-amide had no inhibitory effect on water drinking at this dose.

Atrial natriuretic polypeptide in the brain: implication of central cardiovascular control

Biologically active peptides isolated from peripheral organs often occur in the central nervous system, and vice versa. There is evidence that the effects of centrally active peptides are often, although not always, complementary to their peripheral actions. Atrial natriuretic polypeptide (ANP) is one of these biologically active peptides. Evidence presented here indicates that ANP is involved in the cardiovascular control as a neuropeptide in the central nervous system as well as a circulating hormone in the periphery.

Inhibitory effect of centrally administered atrial natriuretic polypeptide on the brain dopaminergic system in rats

The effects of intracerebroventricular injection of atrial natriuretic polypeptide (ANP) and angiotensin II (AII) on the concentration of dopamine, noradrenaline, serotonin and their primary metabolites in the rat brain were studied using high performance liquid chromatography with electrochemical detection. ANP (2 and 5 micrograms) decreased the level of dopamine and its metabolite in the septum and hypothalamus. In contrast, AII (100 ng) increased their levels in these brain regions. The simultaneous administration of ANP (5 micrograms) with AII (100 ng) resulted in a marked reduction of the AII-induced increase of dopamine and its metabolite. No significant changes were observed in the concentrations of noradrenaline and serotonin throughout the brain. These results suggest that the central action of ANP is mediated in part via the dopaminergic system.