Factor Prohormone Research Articles

Migration and proliferation of human mesenchymal stem cells is stimulated by different regions of the mechano-growth factor prohormone

Stem cell function is thought to be tightly regulated by growth factor concentration in the confines of the microenvironmental niche. Therefore, the response of human mesenchymal stem cells (hMSCs) was studied in culture with mechano-growth factor (MGF), an isoform of IGF-1 known to be expressed in the heart following injury. Chemotactic migration of hMSCs increased in response to a peptide analog corresponding to the E-domain region of the MGF prohormone, which was greater than the IGF-1 polypeptide after 20 h of culture. Compared to control without growth factor, migration was significantly less with a scrambled peptide ( p = 0.025) or a peptide harboring a serine to alanine substitution near the carboxy end ( p = 0.002). The IGF-1 polypeptide increased proliferation of small (5–9 μm) but not large (> 13 μm) hMSCs, whereas the E-domain peptide (MGF-E) had no effect on proliferation. Thus, there are complex biological responses of hMSCs to the prehormone of IGF with respect to migration and proliferation. Since neonatal myocytes but not hMSCs express MGF when strained cyclically at 20%, overloading of the heart may trigger immigration of stem cells. It seems possible that regions of the IGF prohormone may act differentially, or in a combinatorial manner, to benefit cardiac tissue recovery after injury.

Release of atrial natriuretic factor prohormone peptides 1-30, 31-67 and 99-126 from freshwater- and seawater-acclimated perfused trout (Oncorhynchus mykiss) hearts

Atrial natriuretic factor (ANF), a 28-amino-acid peptide hormone produced in the heart, circulates in both freshwater and seawater rainbow trout. In mammals, two other peptide hormones, proANF 1-30 and proANF 31-67, derived from the same 126-amino-acid prohormone as ANF (amino acids 99&shyp;126), circulate and have natriuretic and diuretic properties. It has never been determined whether these peptides circulate in fish. The present investigation was designed to determine (1) whether proANF 1-30 and/or proANF 31-67 circulate in perfused hearts from freshwater- and seawater-acclimated rainbow trout (Oncorhynchus mykiss) in situ, and (2) if they do, to determine whether increasing the filling pressure of the heart causes their release in trout as it does in mammals. High-performance gel-permeation chromatography of fish plasma revealed that both proANF 1-30 and 31-67 circulate in freshwater- and seawater-acclimated trout plasma at threefold higher concentrations than does ANF. The basal rates of release of ANF and proANF 1-30 and 31-67 were similar in both freshwater and seawater trout, with the rate of release of proANF 1-30 being 10 times higher and that of proANF 31-67 20 times higher than that of ANF. When the filling pressure was increased to the peak of the Starling curve (max), the rate of release of ANF and proANFs 1-30 and 31-67 increased fivefold for each peptide in the freshwater trout, while in seawater trout the rates of release increased six- to ninefold. We conclude that proANF 1-30 and 31-67, as well as ANF, circulate in both freshwater-and seawater-acclimated trout and do so at concentrations higher than that of ANF. Increasing the filling pressure to the trout heart was found to cause a similar increase in the release rates for each of these peptides, but the maximal increase was higher in the seawater-acclimated trout, apparently because they showed a larger increase in cardiac output.

Plasma-circulating levels of natriuretic peptides in patients with bone and soft tissue injuries

To evaluate the release and possible role of N-terminal end of atrial natriuretic factor (ANF) prohormone (proANF-1–30) and C-terminal end of ANF prohormone ( aANP-1–28) in patients with soft tissue and bone injuries, 20 patients with soft tissue injuries, 18 bone-fractured patients, and 21 healthy controls were examined. Samples were collected from patients within 24 h after injury. Plasma level of proANF-1–30 and aANP-1–28 were higher in orthopedic patients than the soft tissue injury patients compared to controls ( P < 0.005, P < 0.05, respectively). proANF-1–30 was over 15-fold greater than aANP-1–28 in the healthy control samples. These data hypothesized that the concentration of proANF-1–30 may be related to tissue damages in man.

Modulation of Renin Secretion by A trial Natriuretic Factor Prohormone Fragment 31–67

Background: Earlier studies have indicated that the atrial natriuretic factor prohormone fragment 31-67 (Pro ANF31–67) has important effects for the promotion of sodium excretion and vasodilation in several animal species. However, the mechanisms for the natriuretic actions of Pro ANF31–67 are not completely defined. In the present study, the effects of synthetic Pro ANF31–67 on renin secretion were examined in sodium-depleted, anesthetized dogs with a single intact kidney (n = 5). Methods: After 3 20-minute control renal clearance periods, synthetic dog Pro ANF31–67 was given intrarenally at a sustained dose of 0.03 μg/kg/min for 3 20-minute experimental intervals, and after discontinuation of the peptide infusion, 3 final 20-minute recovery periods were determined. Results: Sustained intrarenal infusions of the Pro ANF31–67 produced striking decrements (p<0.05) in renin secretion, from a control value of 1418 ± 243 to 401 ± 223 ng of angiotensin l/min. This 66% fall in renin secretion was associated with significant (P < 0.05) increases in creatinine clearance (40%), renal blood flow (8%), urine flow (50%), and sodium excretion (17%). Conclusions: It is suggested that this inhibition of renin secretion was mediated, at least in part, in response to a ProANF31–67-induced increment in the sodium load delivered to the macula densa. An interaction of the peptide with the renal vascular receptor for suppression of renin release is also possible. ProANF31–67 may represent an important hormonal mechanism involved in the regulation of body-fluid balance.

Modulation of renin secretion by atrial natriuretic factor prohormone fragment 31-67.

Earlier studies have indicated that the atrial natriuretic factor prohormone fragment 31-67 (Pro ANF31-67) has important effects for the promotion of sodium excretion and vasodilation in several animal species. However, the mechanisms for the natriuretic actions of Pro ANF31-67 are not completely defined. In the present study, the effects of synthetic Pro ANF31-67 on renin secretion were examined in sodium-depleted, anesthetized dogs with a single intact kidney (n = 5). After 3 20-minute control renal clearance periods, synthetic dog Pro ANF31-67 was given intrarenally at a sustained dose of 0.03 microg/kg/min for 3 20-minute experimental intervals, and after discontinuation of the peptide infusion, 3 final 20-minute recovery periods were determined. Sustained intrarenal infusions of the Pro ANF31-67 produced striking decrements (p<0.05) in renin secretion, from a control value of 1418 +/- 243 to 401 +/- 223 ng of angiotensin I/min. This 66% fall in renin secretion was associated with significant (P < 0.05) increases in creatinine clearance (40%), renal blood flow (8%), urine flow (50%), and sodium excretion (17%). It is suggested that this inhibition of renin secretion was mediated, at least in part, in response to a ProANF31-67-induced increment in the sodium load delivered to the macula densa. An interaction of the peptide with the renal vascular receptor for suppression of renin release is also possible. ProANF31-67 may represent an important hormonal mechanism involved in the regulation of body-fluid balance.

Hemodynamic and renal effects of ProANF31-67 in hypertensive rats.

It has been demonstrated previously that the atrial natriuretic factor prohormone fragment 31-67 (ProANF31-67) circulates in animals and possesses natriuretic and vasodilating actions. Although the plasma levels of the peptide are reportedly elevated in patients with high blood pressure, its role and actions in hypertension are unknown. In the present study, synthetic human ProANF31-67 was infused intravenously at doses of 0, 10, 30, and 100 ng/kg/min into respective groups of anesthetized normotensive and spontaneously hypertensive rats. Mean arterial pressure (MAP), urine flow rate (UV), and sodium excretion (UNaV) were measured during two consecutive 30-min periods. In both strains of rats, reductions in MAP with ProANF31-67 were similar in magnitude and dose-related. Sodium excretion responses to the peptide infusions also were remarkably similar in both normotensive and hypertensive rats, and the responses demonstrated 3- to 5-fold (P < 0.05) increments compared to control at the doses of 10 and 30 ng/kg/min. However, in the two strains of rats, attenuation of natriuresis occurred with the highest infusion dose of 100 ng/kg/min and was probably related to the large decreases in MAP of 17-23 mmHg at this dose of the peptide. The present results indicate the ProANF31-67 has important hemodynamic and renal effects in hypertension and may represent one compensatory mechanism involved in this disease.

N-terminal proANF in acute atrial fibrillation: A biochemical marker of atrial pressures but not a predictor for conversion to sinus rhythm

Background: Atrial filling pressures are increased in acute atrial fibrillation, which stimulates the release of atrial natriuretic factor pro-hormone, proANF. Methods: In a randomized trial comparing digoxin with placebo in 216 patients, we investigated whether the baseline plasma level of N-terminal proANF is a predictor for conversion to sinus rhythm and the relation among N-terminal proANF, conversion to sinus rhythm, and changes in heart rate. Results: N-terminal proANF was increased at baseline and decreased significantly in patients converting to sinus rhythm, whereas it was mainly unchanged in nonconverters. N-terminal proANF was not a predictor of conversion to sinus rhythm. A relation was found between relative changes in heart rate and N-terminal proANF in nonconverters. Conclusion: The level of N-terminal proANF does not predict conversion to sinus rhythm, which indicates that hemodynamics per se is not important. There is a correlation between relative changes in heart rate and N-terminal proANF in nonconverters. (Am Heart J 1998;135:1040-7.)

Changes in blood pressure and in vasoactive and volume regulatory hormones during semistarvation in obese subjects

The mechanisms underlying the reduction in blood pressure that occurs with a severe energy-restricted diet were evaluated in 12 obese subjects during 8 days on a very—low-calorie diet (1.67 MJ/d) with a constant intake of 17 mmol sodium per day. The relationship between changes in blood pressure, sodium balance, plasma volume, renin-aldosterone and sympathetic nervous system activities, plasma C-terminus and N-terminus of the atrial natriuretic factor (ANF) prohormone, brain natriuretic peptide (BNP), and endothelin-1 (ET-1) concentrations was investigated. A negative sodium balance was present throughout the diet and was associated with a moderate reduction in plasma volume, a marked activation of the renin-aldosterone system, and a concomitant reduction in C- and N-terminal ANF prohormone levels. Moreover, the postural changes in N-terminal proANF and ANF secretion documented before the diet, disappeared after 8 days of dieting, in contrast to a greater postural stimulation of aldosterone and renin. A negative correlation was found between the changes of C- and N-terminal ANF prohormone levels and those of aldosterone. Urinary catecholamine excretion, BNP, and ET-1 remained unchanged. These results indicate that the decrease in blood pressure occurring during severe caloric restriction was essentially due to the reduction in the effective blood volume, as reflected by the stimulation of the renin-aldosterone system and the decrease in ANF levels. The lack of any changes in catecholamine excretion and endothelin levels suggests that peripheral vascular resistance did not change significantly in these circumstances.

Identification of nerve growth factor prohormone isoforms in gastric juice of rats

Identification of nerve growth factor prohormone isoforms in gastric juice of rats

Commercial mouse and human nerve growth factors contain nerve growth factor prohormone isoforms

Highly sensitive chemiluminescence immunoblot analysis was utilized to examine the purity of mouse 2.5S-, β- and 7S nerve growth factors as well as that of recombinant human β-nerve growth factor obtained from commercial vendors. Three polyclonal antisera and two monoclonal antibodies to 13 kDa nerve growth factor (2.5S NGF and β-NGF) were employed for assessing the purity of each preparation. In addition, polyclonal antisera against two prepro-NGF specific domains were used for immunoblotting analysis to ascertain the identity of high molecular weight nerve growth factor immunoreactive proteins as prohormones. Both the mouse and human NGF preparations contained 53 and 60 kDa immunoreactive proteins. Of these, the mouse 60 kDa and the human 53 kDa proteins strongly immunoreacted with both prepro-nerve growth factor specific domain antibodies suggesting that they are two NGF prohormone isoforms. In addition, both the mouse and human nerve growth factor preparations contained proteins that were immunoreactive to polyclonal antisera and monoclonal antibodies to mouse 2.5S and/or β-NGF. High molecular weight aggregates of prohormones were also observed in mouse and human nerve growth factor samples. In summary, none of the ten NGF samples examined were pure as stated. Our study cautions investigators in the field to be aware of the presence of nerve growth factor prohomones and other proteins in various mouse and human nerve growth factors sold commercially.

Release of atrial natriuretic factor prohormone peptides 1-30, 31-67 and 99-126 from freshwater- and seawater-acclimated perfused trout (Oncorhynchus mykiss) hearts

Atrial natriuretic factor (ANF), a 28-amino-acid peptide hormone produced in the heart, circulates in both freshwater and seawater rainbow trout. In mammals, two other peptide hormones, proANF 1-30 and proANF 31-67, derived from the same 126-amino-acid prohormone as ANF (amino acids 99&shyp;126), circulate and have natriuretic and diuretic properties. It has never been determined whether these peptides circulate in fish. The present investigation was designed to determine (1) whether proANF 1-30 and/or proANF 31-67 circulate in perfused hearts from freshwater- and seawater-acclimated rainbow trout (Oncorhynchus mykiss) in situ, and (2) if they do, to determine whether increasing the filling pressure of the heart causes their release in trout as it does in mammals. High-performance gel-permeation chromatography of fish plasma revealed that both proANF 1-30 and 31-67 circulate in freshwater- and seawater-acclimated trout plasma at threefold higher concentrations than does ANF. The basal rates of release of ANF and proANF 1-30 and 31-67 were similar in both freshwater and seawater trout, with the rate of release of proANF 1-30 being 10 times higher and that of proANF 31-67 20 times higher than that of ANF. When the filling pressure was increased to the peak of the Starling curve (max), the rate of release of ANF and proANFs 1-30 and 31-67 increased fivefold for each peptide in the freshwater trout, while in seawater trout the rates of release increased six- to ninefold. We conclude that proANF 1-30 and 31-67, as well as ANF, circulate in both freshwater-and seawater-acclimated trout and do so at concentrations higher than that of ANF. Increasing the filling pressure to the trout heart was found to cause a similar increase in the release rates for each of these peptides, but the maximal increase was higher in the seawater-acclimated trout, apparently because they showed a larger increase in cardiac output.

Serum N-terminal proatrial natriuretic factor in children with congenital heart disease.

An objective and simple method of establishing and grading heart failure in children is needed. The N-terminal of the atrial natriuretic factor prohormone, called proANF, is stable in vitro, relatively easy to measure and has been demonstrated as a clinically useful marker of heart failure in adults. We measured proANF in 62 children with congenital heart disease and in 62 age-matched controls, in order to examine the relationship of proANF to different clinical and haemodynamic parameters. Echo Doppler cardiography was performed in all children, and 29 also underwent cardiac catheterization. The children were classified for volume and pressure load in each cardiac chamber, for shunt size and for signs of heart failure. In paediatric patients without cardiac or renal disease, median proANF was 384 pmol.l(-1). In children with congenital heart disease, median proANF was 904 (200-5320) pmol.l(-1) (P < 0.001). The three groups with the highest proANF levels were children with documented high atrial pressure (median proANF 1885 pmol.l(-1)), a large left to right shunt (median proANF 1565 pmol.l-(1)) and moderate or severe heart failure (median proANF 1305 pmol.l(-1)). Furthermore, the proANF level correlated negatively with age and glomerular filtration rate. We conclude that elevation of the proANF level is related to atrial pressures, heart failure and a high pulmonary to systemic flow ratio. These findings make proANF a potential new diagnostic tool in heart disease in children.

Atrial Natriuretic Peptide Gene Expression within Invertebrate Hearts

The present investigation was designed to (1) determine if atrial natriuretic factor gene expression occurs within invertebrates as well as within vertebrates; (2) determine whether the product of this gene expression is the 126-amino-acid atrial natriuretic factor prohormone or some other molecular species; and (3) evaluate within the same invertebrates if the products of atrial natriuretic factor gene expression are released into their circulation. Utilizing a very sensitive RNase protection assay it was found that atrial natriuretic peptide gene expression occurs within the heart of the oyster, Crassostrea virginica, and within the heart of the blue crab, Callinectes sapidus , but was expressed sevenfold less than in a vertebrate heart (i.e. rat, Rattus norvegiucs). High-performance gel-permeation chromatography followed by N-terminal and C-terminal atrial natriuretic factor prohormone radioimmunoassays indicated that the molecular species synthesized within the oyster and blue crab hearts was the atrial natriuretic factor prohormone. The product(s) of this atrial natriuretic factor gene expression (i.e., atrial natriuretic peptides) was found to be released into the circulation, i.e., hemolymph, of both the oyster and the blue crab.

Release of kaliuretic peptide during immersion-induced central hypervolemia in healthy humans.

Kaliuretic peptide, a new peptide hormone consisting of amino acids 79-98 of the 126 amino acid atrial natriuretic factor (ANF) prohormone, is synthesized in the heart and is a potent stimulator of potassium excretion. The mechanism(s) controlling the release of kaliuretic peptide heretofore has not been defined. Because water immersion to the neck provides an acute central volume expansion identical to that produced by 2 liters of saline but without the plasma compositional change, immersion to the neck (NI) was utilized to assess kaliuretic peptide responses to acute central blood volume expansion in seven seated sodium-replete normal subjects. Since atrial natriuretic factor (ANF; amino acids 99-126 of the prohormone) originates from the amino acids adjacent to kaliuretic peptide in the ANF prohormone but is proteolytically cleaved from the rest of the prohormone before release, measurement of ANF was incorporated into this study to determine if there are differences with respect to release of these two portions of the ANF prohormone. Both kaliuretic peptide and ANF increased promptly with NI, with ANF peaking at 1 hr of immersion, whereas kaliuretic peptide peaked at the 3rd hr of immersion. With cessation of immersion, ANF decreased to preimmersion levels within 0.5 hr while kaliuretic peptide was still significantly (P < 0.05) elevated at 1 hr postimmersion. These findings indicate that kaliuretic peptide and ANF are released simultaneously but that kaliuretic peptide peak circulating concentration and its return to preimmersion values are prolonged compared with ANF. These last findings suggest a slower clearance from the circulation for kaliuretic peptide. The diuretic peak response to NI corresponded in a temporal manner to the peak circulating concentration of kaliuretic peptide, suggesting a possible physiologic role for kaliuretic peptide in modulating volume homeostasis in humans.

Localization of epidermal growth factor (EGF) prohormone in feces adhering to the site of inflammation in an experimental model of rat colitis

Localization of epidermal growth factor (EGF) prohormone in feces adhering to the site of inflammation in an experimental model of rat colitis

Effects of ANF prohormone peptides in conscious primates.

1. Recent studies suggest that amino-terminal peptides from the atrial natriuretic factor (ANF) prohormone are natriuretic. 2. The effects of pro ANF 31-67 and ANF 99-126 on renal function were studied in conscious non-human primates (Macaca fascicularis). 3. Results show that pro ANF 31-67 and ANF 99-126 are diuretic and natriuretic and that when the two peptides are given in combination sodium excretion increases in an additive fashion. 4. These results indicate that multiple peptides from the ANF prohormone are natriuretic. Furthermore, these findings suggest that the combined action of these peptides causes the natriuresis that occurs after the release of endogenous atrial peptides.

Temporal (circadian) and functional relationship between atrial natriuretic peptides and blood pressure.

Long-acting natriuretic peptide, vessel dilator, and atrial natriuretic factor consisting of amino acids (a.a.) 1 to 30, 31 to 67, and 99 to 126 of the 126-a.a. atrial natriuretic factor (ANF) prohormone, respectively, circulate in humans and have potent vasodilatory properties. To determine if these atrial natriuretic peptides are directly related to blood pressure in clinically healthy normotensive humans, we obtained 24-h profiles of vessel dilator, long-acting natriuretic peptide, ANF, and blood pressure in 10 men in 1988 and 11 men in 1993 (seven men were studied twice) to compare circulating concentrations of atrial natriuretic peptides with naturally occurring changes in blood pressure. Overall, vessel dilator, long-acting natriuretic peptide, and ANF each had significant (p<0.001) circadian rhythms, with peak concentrations late during sleep (at 04:00 h) being nearly twice their concentrations in the afternoon and evening. This high-amplitude circadian change allowed for the refinement of normal limits for ANF peptides by computing 3-hourly tolerance intervals (chronodesms) against which to compare time-specified single samples for normality. Systolic, diastolic, and mean arterial blood pressure also had significant circadian rhythms (p<0.001) with peaks and troughs that were exactly opposite those of the ANF peptides. In addition to this inverse temporal relationship, there was a significant inverse correlation between absolute values for blood pressure and each ANF peptide (p<0.001), implying a functional relationship. These data suggest that in addition to other well-established neurochemical factors, the ANF peptides (vessel dilator, long-acting natriuretic peptide, and ANF) are important for the maintenance of blood pressure and modulation of its circadian rhythm.

Three peptides from the atrial natriuretic factor prohormone amino terminus lower blood pressure and produce diuresis, natriuresis, and/or kaliuresis in humans.

Three peptides consisting of amino acids 1-30, 31-67, and 79-98 of the 126-amino acid atrial natriuretic factor prohormone (proANF), which have blood pressure-lowering, diuretic, natriuretic, and/or kaliuretic properties in animals, were investigated to determine if they have similar properties in humans. Thirty-six healthy, normotensive human volunteers (18 men and 18 women, ages 20 to 58 years) were divided into six similar groups based on age, sex, weight, blood pressure, and heart rate. After a 60-minute baseline period, 100 ng of proANFs 1-30, 31-67, 79-98, or ANF/kg body wt per minute was given intravenously for 60 minutes followed by a 3-hour postinfusion data collection period. Each of the atrial natriuretic peptides decreased systolic and diastolic blood pressures (P < .05), with proANF 31-67 causing the largest decrease. Urine flow increased 4- to 12-fold and was still significantly increased (P < .01) for 2 to 3 hours after stopping the respective infusions of proANFs 1-30, 31-67, and 79-98. Atrial natriuretic factor (ANF) increased urine flow 4- to 11-fold but by 2 hours after infusion was significantly increased in only 1 of 6 subjects. Sodium excretion increased 3- to 8-fold, 3- to 6-fold, 0- to 2-fold (NS), and 3- to 11-fold, respectively, with proANFs 1-30, 31-67, 79-98, and ANF. Natriuretic effects of proANFs 1-30 and 31-67 were significantly prolonged (P < .001) compared with ANF. ProANFs 1-30, 31-67, 79-98, and ANF increased potassium excretion 2- to 3-fold, 0-fold, 3- to 4-fold, and 2-fold, respectively. High-performance gel permeation chromatography followed by the respective radioimmunoassays revealed that proANFs 1-30, 31-67, 79-98, and 68-98, as well as ANF circulate as distinct peptides. ProANFs 1-30, 31-67, and 79-98, as well as ANF have significant blood pressure-lowering and diuretic properties. ProANFs 1-30 and 31-67 also have natriuretic properties in humans that are significantly (P < .001) prolonged compared with ANF. ProANF 79-98, although not possessing any natriuretic property, is the strongest stimulator of potassium excretion of the four atrial natriuretic peptides.

Alteration of environmental salinity modulates atrial natriuretic peptides concentrations in heart and hemolymph of the oyster, Crassostrea virginica

Atrial natriuretic peptides (ANPs) measured in the circulation (hemolymph) of eastern oysters, Crassostrea virginica, by radioimmunoassays devised to detect amino acids 1–30, 31–67 and 99–126 (i.e. ANF) of the 126 amino acid atrial natriuretic factor prohormone were increased 100% in animals held in a high salinity environment (32 ppt), and decreased 50% in low salinity environment (8 ppt) relative to a medium (21 ppt) salinity. Within the oyster heart tissue, the concentration of ANPs decreased ( P < 0.01) at 3 days and then increased ( P < 0.01) at 1 and 2 weeks in high versus medium salinity. In 8 ppt external salinity, ANPs were significantly decreased ( P < 0.01) compared to 21 ppt and 32 ppt salinities at each time period. ANPs increase and decrease within the hemolymph in direct relationship to environmental salinity, with their decrease in heart tissue at 3 days of high salinity suggesting release of stored forms that are re-synthesized by 1 week, while in low salinity environment ANP synthesis is decreased.

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.