Atrial natriuretic peptides and cyclic guanosine monophosphate metabolism.

Atrial natriuretic factor (ANF), consisting of amino acids 99-126 of the 126 amino acid ANF prohormone, increases cyclic guanosine monophosphate (GMP) (thought to be the mediator of its physiologic effects) in plasma and urine of human subjects. Long-acting natriuretic peptide, vessel dilator, and kaliuretic peptide, consisting of amino acid 1-30, 31-67, and 79-98, respectively, of this same prohormone have natriuretic, diuretic, kaliuretic, and blood pressure lowering properties in humans. These three new peptide hormones increase cyclic GMP in vitro but were never investigated to determine whether they also cause extrusion of cyclic GMP from cells, resulting in an increase of cyclic GMP in plasma and/or urine. Infusion of each of these peptide hormones at their 100 ng/kg body weight/min concentrations for 60 minutes into healthy humans resulted in a sevenfold increase in cyclic GMP in plasma and urine secondary to ANF, but no significant increase secondary to the other atrial peptide hormones. Based on the current data, ANF has a unique effect on the metabolism of cyclic GMP, causing it to be extruded from the cell, whereas the other three atrial peptides represent the more classical metabolism of cyclic GMP via cyclic GMP phophodiesterases.

Increase in atrial natriuretic factor in the lungs, heart, and circulatory system owing to ozone.

Ozone can cause pulmonary edema and simultaneously decrease blood pressure. Atrial natriuretic factor (ANF) may mediate both of these effects in that it increases pulmonary capillary permeability resulting in edema formation and vasodilates the vascular system. The present investigation was designed to test directly the effect of ozone on the content of ANF in the lungs, heart, and the circulatory system. Ozone (0.5 ppm) exposure for 8 h increased ANF content in the lungs fourfold (13.33 +/- 2.7 ng/g tissue) in six Fischer 344 rats compared with ANF content (3.03 +/- 0.2 ng/g tissue) in six Fischer 344 rats exposed only to room air. Ozone increased ANF content in the heart fivefold in the same animals from 288 +/- 39.6 ng/g tissue in the rats exposed to room air to 1,473 +/- 234.8 ng/g tissue in those exposed to ozone. Ozone also doubled the concentration of ANF in the circulatory system. This study demonstrates that ozone does increase ANF in the lungs, heart, and circulatory system, suggesting that ANF may mediate the decreased blood pressure and pulmonary edema observed with ozone exposure.

Negative feedback of atrial natriuretic peptides.

The present investigation was designed to determine whether atrial natriuretic peptides consisting of amino acids 1-30 [i.e. pro-ANF-(1-30)], 31-67 [i.e. pro-ANF(31-67)], 79-98 [i.e. pro-ANF-(79-98)], and 99-126 [i.e. atrial natriuretic factor (ANF)] of 126-amino acid ANF prohormone have a negative feedback on their own and each others' release. Thirty healthy human subjects were studied with infusion of 100 ng/kg BW.min for 60 min of each of the respective peptides. Pro-ANF-(1-30) decreased the circulating concentrations of pro-ANF-(31-67) and ANF 51% and 89%, respectively. Pro-ANF-(31-67) decreased the circulating concentration of ANF by 55% and the peptides immunologically recognized by the pro-ANF-(1-30) RIA by 58% [this assay recognizes pro-ANF-(1-30) (50%) and pro-ANF-(1-98) (50%)]. Pro-ANF-(79-98) decreased the circulating concentration of ANF by 40%, pro-ANF-(31-67) by 31%, and the peptides recognized by the pro-ANF-(1-30) RIA by 46%. ANF decreased the circulating concentration of pro-ANF-(31-67) by 40% and the peptides recognized by pro-ANF-(1-30) RIA by 38%. Infusion of pro-ANF-(1-30), -(31-67), -(79-98), and -(99-126) also decreased the excretion of the other atrial natriuretic peptides measured in the urine by 32-84%. Infusion of vehicle only did not result in any decrease in these atrial natriuretic peptides in either plasma or urine. These data taken together indicate that each of the respective atrial natriuretic peptides inhibits the release, rather than breakdown, of each other, as increased breakdown would have resulted in their urinary concentrations being increased. This study further indicates that because pro-ANF-(1-98) was decreased in the circulation secondary to pro-ANF-(31-67) and pro-ANF-(79-98) infusions, they inhibit their own release, as they are both derived from pro-ANF-(1-98).

Ozone increases amino- and carboxy-terminal atrial natriuretic factor prohormone peptides in lung, heart, and circulation.

Ozone can cause pulmonary edema and simultaneously decrease blood pressure. Atrial natriuretic peptides may mediate both of these effects in that they increase pulmonary capillary permeability resulting in edema formation and are potent vasodilating peptides. To examine this possibility, the lungs of Fischer 344 rats were exposed to ozone (0.5 ppm) for 8 hours which resulted in a three- to fourfold increase in atrial natriuretic peptides. Ozone also increased atrial natriuretic peptides in the heart two- to fivefold from 266 +/- 25, 226 +/- 22, and 288 +/- 40 ng/g (room air) to 716 +/- 26, 471 +/- 14, and 1473 +/- 235 ng/g recognized by the proANFs 1-30 and 31-67 and atrial natriuretic factor radioimmunoassays, respectively. Ozone also doubled the concentrations of pro-ANFs 1-30, 31-67, and 1-98 and ANF in the circulation. This study demonstrates that ozone increases atrial natriuretic peptides within the heart, lung, and circulation, suggesting that atrial natriuretic peptides may mediate the decreased blood pressure and pulmonary edema observed with ozone exposure. Since the proANF 31-67 radioimmunoassay exclusively recognizes the ANF prohormone within the heart, this study further indicates that ozone can increase the synthesis of the ANF prohormone.

Ozone increases atrial natriuretic peptides in heart, lung and circulation of aged vs. adult animals.

Ozone can cause pulmonary edema and simultaneously decrease blood pressure. Atrial natriuretic peptides may mediate both of these affects since they increase pulmonary capillary permeability and are potent vasodilating peptides. To examine this possibility and determine if aged animals respond differently to ozone, adult (4-6 months old) and aged (24-26 months old) Fischer 344 rats were exposed to ozone (0.5 parts per million) for 8 h. Ozone increased atrial natriuretic peptides recognized by the proANF 1-30, proANF 31-67, and atrial natriuretic factor (ANF) radioimmunoassays in lung from 3.7 +/- 0.2, 3.5 +/- 0.1, and 3.0 +/- 0.2 ng/g of lung, respectively, to 9.7 +/- 1.0, 9.2 +/- 0.4, and 13.3 +/- 2.7 ng/g in adult rats (n = 6) and from 3.6 +/- 0.1, 3.5 +/- 0.1, and 3.2 +/- 0.1 ng/g of lung of aged rats (n = 6) to 10.2 +/- 0.3, 10.0 +/- 0.2, and 12.6 +/- 0.2 ng/g. Ozone increased the content of these peptides in the heart 2- to 5-fold from 266 +/- 25, 226 +/- 22, and 288 +/- 40 ng/g of heart to 716 +/- 26, 471 +/- 14, and 1,473 +/- 235 ng/g in the same adult animals and from 495 +/- 17, 483 +/- 22, and 501 +/- 18 ng/g to 903 +/- 16,879 +/- 21, and 1,489 +/- 31 ng/g of heart in the aged animals. Ozone also doubled the concentration of these atrial natriuretic peptides in the circulatory system. This study demonstrates that ozone increases atrial natriuretic peptides in the lung, heart, and circulation of equal magnitude in aged versus adult animals, indicating an equal response to ozone with aging. This study further suggests that atrial natriuretic peptides may mediate the decreased blood pressure and pulmonary edema observed with ozone exposure.

Normalization of circulating atrial natriuretic peptides in cardiac transplant recipients.

To assess whether heart transplantation (Htx) alters the marked elevation of circulating atrial natriuretic peptides usually found in patients with congestive heart failure (CHF), 14 subjects (nine with compensated and five with decompensated CHF), each with an ejection fraction < or = 28%, were evaluated. Immediately before and hourly for the first 12 hours after Htx, then daily for 21 days and every 1 to 4 weeks for 6 months, the circulating concentrations of the N-terminus (pro atrial natriuretic factor [ANF] 1-98), midportion of the N-terminus (pro ANF 31-67), and C-terminus (that is, ANF) of the 126 amino acid prohormone were measured. Increased (p < 0.001) levels of these peptides were found in superior vena cava, right atrial, and peripheral venous samples 1 hour after Htx in all subjects except one. The atrial natriuretic peptide levels correlated only with right atrial pressure (p < 0.01) in the first 24 hours. Circulating concentrations of these peptides returned to those of healthy adults between 5 and 12 days after Htx in 11 out of 14 Htx recipients. Thus successful Htx can restore the elevated circulating concentrations of atrial natriuretic peptides to those of healthy adults.

Atrial natriuretic peptides in the heart and hemolymph of the oyster, Crassostrea virginica: a comparison with vertebrates.

1. The content of atrial natriuretic peptides (ANPs) in the auricles of oysters, Crassostrea virginica, was significantly (P < 0.01) greater than in their ventricles. 2. High-performance gel permeation chromatography (HP-GPC) followed by ANF radioimmunoassay revealed two peaks in both oyster and vertebrate (rat) hearts--a major peak where the 12.6-14 kDa ANF prohormone elutes and a smaller peak where the pure human form of ANF elutes. 3. HP-GPC evaluation followed by proANF 31-67 radioimmunoassay revealed only an ANF-like prohormone while HP-GPC followed by proANF 1-30 radioimmunoassay revealed the ANF prohormone and a proANF 1-30-like peptide in oyster and rat hearts. 4. ANPs concentrations in hemolymph were 940 +/- 129, 225 +/- 25, and 100 +/- 10 pg/ml by the proANF 1-30, proANF 31-67, and ANF radioimmunoassays, respectively. 5. Atrial natriuretic-like peptides are present in the oyster heart in molecular species similar to vertebrate species and these peptides are also present in hemolymph.

Atrial natriuretic peptides are present throughout the plant kingdom and enhance solute flow in plants.

The present investigation was designed to 1) determine if atrial natriuretic-like peptides are present throughout the plant kingdom and 2) to determine if these peptides increase the flow of solute and/or water upward to leaves and flowers of plants. The 126-amino acid prohormone of atrial natriuretic factor (proANF)-(1-30), proANF-(31-67), and atrial natriuretic factor (ANF)-like peptides were present in the roots, stems, leaves, and flower petals of the more highly developed plants (Tracheophyta), with their highest concentrations being: Florida beauty > buddhist pine > Boston fern > rose = geranium = resurrection plant or club moss > Moses-in-the-cradle > Florida coontie. These peptides were also present in Bryophata (plants without vascular tissue or roots) and even in Euglena, flagellated chlorophyll-containing plants without leaves, stems, or roots. proANF-(1-30), proANF-(31-67), and proANF-(79-98) but not ANF (each at < 5.9 pg/ml) significantly increased (P < 0.001) the flow of colored water up stems, coloring their flowers 15-35 min earlier than the other one-half of the same flowers without exogenous peptide addition. These same peptides increased the rate of transpiration (i.e., loss of water from the leaves) and the absorption of solutions. High-performance gel permeation chromatography revealed that proANF-(1-30), proANF-(31-67), and ANF extracted from plants are very similar to their pure synthetic human sequences, with elution profiles and molecular weights of the plant extracts duplicating those of the pure synthetic peptides.

Increased atrial natriuretic factor prohormone peptides with aging in the heart, but not in lung, liver, or intestine.

Atrial natriuretic factor (ANF) has been found to be increased in the circulation of aged rats. The present investigation was designed to determine if the N-terminal ANF prohormone peptides with blood pressure lowering properties are increased in the circulation of "aged" (24-26 months) versus "adult" (4-6 month old) Fisher 344 rats. We utilized two sensitive and specific radioimmunoassays that immunologically recognize the 98 amino acid (a.a.) N-terminus (proANF 1-98) and a.a. 31-67 (proANF 31-67, Vessel dilator) from the midportion of the N-terminus of the 126 a.a. ANF prohormone. ProANF 1-98, and proANF 31-67, as well as ANF, were found to be elevated in the circulation of aged versus adult animals with proANF 31-67 and ANF elevations being significant at p < 0.05. To determine the potential source of the increased atrial natriuretic peptides in aged animals four tissue sources (liver, lung, heart, and intestine) from both adult and aged animals were examined. Hearts of aged animals contained significantly (P < 0.05; ANOVA) more proANF 1-98, proANF 31-67, and ANF than hearts of adult animals. There was no significant difference in the concentration of proANF 1-98, proANF 31-67, or ANF in the lung, liver, or intestine of the aged versus the adult animals. These results indicate that aged animals contained increased N-terminal and C-terminal ANF prohormone peptides in the circulation. The source of these increased peptides appears to be the heart.

The most primitive heart in the animal kingdom contains the atrial natriuretic peptide hormonal system.

1. The newly described atrial natriuretic peptide hormonal system appears to play an important role in the endocrine control of sodium and water metabolism in human and vertebrate animals, but neither atrial natriuretic factor (ANF, C-terminal amino acids (a.a.) 99-126 a.a. prohormone) nor the rest of the ANF prohormone have ever been demonstrated in the heart of an invertebrate. 2. The present investigation was designed to determine whether the earthworm, Lumbricus terrestis, the first animal in the phylogenic tree with any form of heart, has either ANF and/or the 98 a.a. N-terminus of the ANF prohormone. 3. Both an ANF-like peptide (189 +/- 32 ng/g of tissue) and the N-terminus of the ANF prohormone-like peptide (1985 +/- 27 ng/g of tissue) were present in the earthworm heart at concentrations significantly higher (P less than 0.001) than in rat (Rattus norvegicus) heart ventricles. 4. This newly-described hormonal system, thus, appears to be present in a much larger proportion of the animal kingdom than previously thought, including invertebrates as well as vertebrates.

Atrial natriuretic factor-like peptide and its prohormone within single cell organisms.

The present investigation was designed to determine if the atrial natriuretic peptide hormonal system is present within single cell organisms. Paramecium multimicronucleatum were examined with 3 sensitive and specific radioimmunoassays which recognize the N-terminus [amino acids 1-98; proANF(1-98)], the midportion of the N-terminus [amino acids 31-67; proANF(31-67)] and C-terminus (amino acids 99-126; ANF) of the 126 amino acid atrial natriuretic factor (ANF) prohormone. ProANF(1-98), proANF(31-67), and ANF-like peptides were all present within these unicellular organisms at concentrations of 460 +/- 19 pg/ml, 420 +/- 15 pg/ml, and 14.5 +/- 2 pg/ml, respectively. These concentrations are similar to their respective concentrations in the plasma of the rat (Rattus norvegicus). These results suggest that even single cell organisms contain the atrial natriuretic peptide-like hormonal system.

Atrial natriuretic factor prohormone peptides are present in a variety of tissues.

Utilizing two sensitive and specific radioimmunoassays which immunologically recognize 1) the 98 amino acid (a.a.) N-terminus and 2) the 28 a.a. C-terminus (i.e., a.a. 99-126) of the 126 a.a. atrial natriuretic (ANF) prohormone, various tissues including aorta, kidney, small intestine, colon, liver, spleen, lung, and testis were investigated to determine if the ANF prohormone was present in any of these tissues in addition to its previously demonstrated presence in heart and brain. Aorta with 62.3 +/- 3 ng of the N-terminus/g of tissue and 51.6 +/- 1.8 ng of the C-terminus of the ANF prohormone/g of tissue had the highest concentration of the ANF prohormone of the previously undescribed ANF prohormone-containing tissues. The next highest concentration of the ANF prohormone was in the intestine, followed by lung and spleen. Pancreas, liver and kidney had similar levels of immunologically recognized ANF prohormone (approximately 1/50 of the aorta), while the testis and cerebrum had low levels. These results suggest that a much larger variety of tissues synthesize and/or store the ANF prohormone than is presently thought.

Atrial natriuretic factor: a possible new gastrointestinal regulatory peptide.

Although associated primarily with the cardiovascular system, atrial natriuretic factor (ANF) has been found to increase the magnitude of duodenal contractions and may play a role in salt and water absorption across gastrointestinal epithelium. Because secretory diarrhea and increased peristalsis are commonly associated with conditions related to hypergastrinemia, we examined an animal model of hypergastrinemia (fundusectomy) to evaluate a possible role for ANF. Sprague-Dawley rats underwent either fundusectomy or sham operation. Circulating levels of gastrin (1085 +/- 105 vs 59 +/- 5 pg/ml), ANF (209 +/- 50 vs 59 +/- 10 pg/ml), and pro-ANF 1-98 (786 +/- 80 vs 599 +/- 49 pg/ml) were elevated significantly 3 months after fundusectomy versus control animals. The increased levels of ANF and pro-ANF 1-98 correlated with the increased gastrin levels (p less than 0.05). Tissue content of ANF and pro-ANF 1-98 were determined at sequential sites in the stomach and small intestine. In normal rats ANF concentrations were greatest in the small intestine; pro-ANF 1-98 content was similar in all tissues except ileum (increased). In rats that underwent fundusectomy, ANF and pro-ANF 1-98 were markedly increased in duodenum compared with all other tissues. Only duodenum showed a difference in peptide levels between normal rats and rats that underwent fundusectomy, (ANF, 1.5 +/- 0.5 vs 16.7 +/- 2.3 ng/gm; pro-ANF 1-98, 0.6 +/- 0.3 vs 51.2 +/- 36.1 ng/gm). Circulating ANF and pro-ANF 1-98 are increased in rats that have undergone fundusectomy. Our results suggest that duodenum may be the source of these increased levels.

Atrial natriuretic peptide hormonal system in plants.

To determine if atrial natriuretic peptides are present in plants as well as animals, where they are important for water and sodium metabolism, the leaves and stems of the Florida Beauty (Dracena godseffiana) were examined. The N-terminus consisting of amino acids (a.a.) 1-98 (i.e., pro ANF 1-98), the mid portion of the N-terminus (a.a. 31-67; pro ANF 31-67), and C-terminus (a.a. 99-126; ANF) of the 126 a.a. atrial natriuretic factor (ANF) prohormone were all present in the leaves and stems of this plant. The concentrations of pro ANF 1-98, pro ANF 31-67 and ANF-like peptides of 120 +/- 20, 123 +/- 21, and 129 +/- 20 ng/g of plant tissue in leaves and 109 +/- 20, 96 +/- 21, and 124 +/- 18 ng/g of tissue, respectively, in the stems were lower (P less than 0.05) than their concentrations in rat (Rattus norvegicus) heart atria of 196 +/- 40, 192 +/- 28, and 189 +/- 15 ng/g of tissue respectively, but higher (P less than 0.001) than their respective concentrations of 4.3 +/- 1.4, 4.1 +/- 1.2, and 3.9 +/- 1 ng/g of rat heart ventricular tissue. We conclude that the atrial natriuretic peptide-like hormonal system is present in the plant kingdom as well as in the animal kingdom.

Food intake and body positional change alter the circadian rhythm of atrial natriuretic peptides excretion into human urine.

The 98 amino acid (a.a.) N-terminus of the 126 a.a. atrial natriuretic factor prohormone contains two natriuretic and vasodilatory peptides consisting of a.a. 1-30 (proANF 1-30) and a.a. 31-67 (proANF 31-67). The N-terminus and C-terminus (a.a. 99-126, i.e., ANF--also a vasodilatory peptide) circulate normally in humans with a circadian peak at 04:00 h in plasma. To determine if the N-terminus and C-terminus of the ANF prohormone are present in urine and possibly have a circadian variation in urine, six healthy volunteers had urine samples hourly while awake and every 3 h during sleep for five consecutive days obtained for radioimmunoassay. The sleep-awake pattern was varied so that after 2 days of normal sleep (supine)-awake (upright) positions, these volunteers were supine from 15:00 h on the third day until 10:00 h of the fourth day. They were then upright until 19:00 h that day when they became supine again until 02:30 h, and then were upright until 10:00 h of day 5. Three radioimmunoassays that immunologically recognize (a) the whole N-terminus (i.e., amino acids 1-98), (b) the midportion of the N-terminus (amino acids 31-67), and (c) the C-terminus of the ANF prohormone were utilized. ProANF 1-98, proANF 31-67, and the ANF radioimmunoassays each detected their respective peptides in urine. A circadian peak for each of these peptides was detected at 04:00 to 05:00 h whether the person was supine or upright during the night, which were significantly (p less than 0.001) higher than their concentrations in the afternoon of the previous days. Assuming a supine position during the day caused a significant (p less than 0.01) two- to threefold increase in these peptides in the urine. Food intake also increased the concentrations of proANF 1-98, proANF 31-67, and ANF in urine (p less than 0.001). Fluid intake when abstaining from food throughout the day lowered the concentration of these peptides in the urine. It was concluded that there is a circadian rhythm in both the N-terminus and C-terminus of the ANF prohormone excretion into urine with a peak at 04:00 h irrespective of posture, but that both posture and food and fluid intake throughout the day significantly influence the excretion of these peptides into the urine, with supine posture and food increasing their concentrations in the urine while fluid intake decreases their concentrations in the urine.