Circadian Rhythm of Prohormone Atrial Natriuretic Peptides 1-30, 31-67 and 99-126 in Man

Two peptides consisting of amino acids 1-30 and 31-67 of the N-terminal end of the prohormone of the atrial natriuretic factor (pro ANF), vasodilate aortas in vitro, lower blood pressure in vivo, and have natriuretic properties similar to the atrial natriuretic factor (ANF, amino acids 99-126 of the prohormone). It has been recently discovered that pro ANF 1-30 and pro ANF 31-67 as well as ANF circulate in man. To determine if these three peptide hormones have a circadian variation in their circulating plasma concentrations, eight housestaff volunteers were studied on a day when they were in the hospital for 24 hr. These 5 men and 3 women, ages 25 to 39 had blood samples taken at 0800, 1200, 1600, 2000, 0000, 0400 and 0800 on the following day. One-half of these house officers were up all night while the other half went to sleep from midnight to 0800 and had their 0400 plasma samples drawn while in a supine position. The peak level for all three peptide hormones was at 0400 for both supine and upright subjects. It was concluded that there are circadian rhythms in normal, active people of these three peptide hormones, whose peak levels are at 0400 irrespective of posture.     

Circadian Rhythm of Prohormone Atrial Natriuretic Peptides 1-30, 31-67 and 99-126 in Man

Two peptides consisting of amino acids 1-30 and 31-67 of the N-terminal end of the prohormone of the atrial natriuretic factor (pro ANF), vasodilate aortas in vitro, lower blood pressure in vivo, and have natriuretic properties similar to the atrial natriuretic factor (ANF, amino acids 99-126 of the prohormone). It has been recently discovered that pro ANF 1-30 and pro ANF 31-67 as well as ANF circulate in man. To determine if these three peptide hormones have a circadian variation in their circulating plasma concentrations, eight housestaff volunteers were studied on a day when they were in the hospital for 24 hr. These 5 men and 3 women, ages 25 to 39 had blood samples taken at 0800, 1200, 1600, 2000, 0000, 0400 and 0800 on the following day. One-half of these house officers were up all night while the other half went to sleep from midnight to 0800 and had their 0400 plasma samples drawn while in a supine position. The peak level for all three peptide hormones was at 0400 for both supine and upright subjects. It was concluded that there are circadian rhythms in normal, active people of these three peptide hormones, whose peak levels are at 0400 irrespective of posture.     

Specific binding sites for prohormone atrial natriuretic peptides 1-30, 31-67 and 99-126

Two peptides with vasodilatory properties consisting of amino acids 1-30 and 31-67 of the 98 a.a. N-terminal end of the prohormone of atrial natriuretic factor (proANF) which circulates in man were investigated to determine if they have specific binding sites on membranes isolated from DDT1 MF-2 smooth muscle cells. Smooth muscle is a known biologic target of these peptides. Competitive binding experiments revealed that proANFs (1-30), (31-67), and (99-126) (i.e., C-terminus; ANF) each had specific and separate binding sites. The dissociation constants for proANFs (1-30), (31-67), and (99-126) binding were 0.11 nM, 4 nM, and 7.3 nM, respectively. The binding site concentrations for proANFs (1-30), (31-67), and ANF were 2.57, 59.91 and 40 fmols/10(6) cells, respectively. The number of binding sites per cell were 1548, 36,087, and 24,090, respectively, for proANFs (1-30), (31-67), and (99-126) (ANF). Each peptide bound to DDT1 MF-2 membranes between 10(-8) to 10(-11) M but could only bind to the other peptides' receptors at concentrations of 10(-6) and 10(-7)M. These results suggest that proANF(1-30) and proANF(31-67) do not work through the ANF receptor but rather have their own separate and distinct receptors that mediate their biologic effects.     

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.     

Atrial natriuretic prohormone peptides 1-30, 31-67, and 79-98 vasodilate the aorta

Human prohormone atrial natriuretic peptides 1-30, 31-67, and 79-98 caused vasodilation of porcine aortas which began in 30 seconds and was maximal at 10 minutes. These three peptides were found to be equally potent to atrial natriuretic factor in their vasodilatory activity which was found with or without endothelium present. This vasodilation was associated with a 4 to 5 fold increase in cyclic GMP in the aorta secondary to activation of particulate guanylate cyclase [E.C. 4.6.12]. These data demonstrate that three N-terminal peptide segments of the atrial natriuretic factor prohormone cause vasodilation.     

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

• 1.1. The content of atrial natriuretic peptides (ANPs) in the auricles of oysters, Crassostrea virginica, was significantly (P < 0.01) greater than in their ventricles.
• 2.2. 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.
• 3.3. 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.
• 4.4. 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.
• 5.5. 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.

     

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.     

Novel N-terminal fragments of pro-gamma-melanocyte-stimulating hormone isolated from pig pituitary

Two novel N-terminal fragment pairs of porcine pro-gamma-melanocyte-stimulating hormone (MSH)-(1-103), viz. pro-gamma-MSH-(1-30)/(2-30) and pro-gamma-MSH-(1-67)/(2-67) were characterized. A third pair of peptides of still larger size was also detected. The two characterized peptide pairs terminate at sites different from the dibasic sequences typical of prohormone cleavage. This suggests either a different processing event or proteolysis during purification; in both cases cleavages are selective since the two peptides end at distinct positions. Unlike most previously described pro-gamma-MSH forms, which begin with Trp at position 1 in pro-opiomelanocortin (position -105 in relation to the start of ACTH), the novel peptide pairs show N-terminal heterogeneity with one of the components beginning with Trp as in other forms, and the second component (present in relative amounts of 10-70%) beginning with Cys at position 2 (corresponding to position -104).     

Two new hormones: prohormone atrial natriuretic peptides 1-30 and 31-67 circulate in man

Two peptides consisting of amino acids 1-30 and 31-67 of the N-terminal end of the prohormone of atrial natriuretic factor (pro ANF) which vasodilate aortas in vitro, lower blood pressure in vivo, and have natriuretic properties were found to circulate in 54 normal human volunteers. The mean circulating concentration of pro ANF 1-30 was 1861 +/- 87 pg/ml (SEM) while pro ANF 31-67 mean concentration was 1478 +/- 71 pg/ml versus a level of 67 +/- 3 pg/ml for atrial natriuretic factor (ANF). In chronic renal failure their mean concentrations increased to 40,484 +/- 6,929 pg/ml (SEM), 108,566 +/- 16,888 pg/ml, and 348 +/- 81 pg/ml for pro ANFs 1-30 and 31-67 and ANF respectively. Since pro ANF 1-30 and pro ANF 31-67 circulate in man and have physiologic effects they meet the criteria of two new hormones.     

The circadian rhythm of the N-terminus and C-terminus of the atrial natriuretic factor prohormone

Circadian variation in the circulating concentrations of the N-terminal and C-terminal portions of the atrial natriuretic factor prohormone (pro ANF) was evaluated in 8 men, ages 41-47, who have been followed for 19 years with respect to circadian variation in physiological variables including blood pressure and clinical chemistries. The N-terminus of the ANF prohormone contains two peptides consisting of amino acids 1-30 and 31-67 while the C-terminus contains 1 peptide (amino acids 99-126) of this 126 amino acid prohormone which lower blood pressure and have natriuretic properties. To determine if either the N-terminus and/or the C-terminus of the prohormone have a circadian variation in their circulating plasma concentrations these 8 men had blood samples obtained for radiommunoassay every 3 hr during a 24-hr period. Three radiommunoassays which immunologically recognize (1) the whole N-terminus (i.e. amino acids 1-98), (2) the midportion of the N-terminus (amino acids 31-67) and (3) the C-terminus (amino acids 99-126) of the ANF prohormone were utilized. The whole N-terminus, the midportion of the N-terminus which circulates after being proteolytically cleaved from the rest of the N-terminus, and the C-terminus each had a peak circulating concentration between 0400 and 0700 which were significantly (P less than 0.001) higher than their concentrations at any other time throughout the 24-hr period.(ABSTRACT TRUNCATED AT 250 WORDS)     

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 proANFs 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.     

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 < 0.001) higher than their concentrations in the afternoon of the previous days. Assuming a supine position during the day caused a significant (p < 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 < 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.     

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.     

Increased release of the N-terminal and C-terminal portions of the prohormone of atrial natriuretic factor during immersion-induced central hypervolemia in normal humans

The role of peptides from the N terminus and C terminus of the 126 amino acid atrial natriuretic factor (ANF) prohormone in modulating renal sodium and water handling has not been defined. Since water immersion to the neck (NI) provides an acute central volume expansion identical to that produced by 2 liters of saline but without plasma compositional change, immersion to the neck was used to assess the N-terminal and C-terminal portions of the ANF prohormone response to acute central blood volume expansion in seven seated sodium-replete normal subjects. Both the C terminus, which contains amino acids 99-126 and is identical to ANF, and the whole N terminus (i.e., amino acids 1-98) increased promptly with NI and peaked after 1 hr of immersion. A Mr 3900 peptide from the midportion of the N terminus consistent with amino acids 31-67 (i.e., pro-ANF-31-67) also increased with NI and followed a pattern of increasing circulating concentration nearly identical to that of the whole N terminus of the prohormone, except that its maximal concentration was at the second hour of the 3 hr of NI. With cessation of immersion, ANF decreased to preimmersion levels within 1 hr whereas the N terminus and pro-ANF-31-67, although their circulating concentrations were decreasing, were still significantly elevated at 1 hr. These findings suggest that the increase in plasma ANF, the N terminus of the ANF prohormone, and pro-ANF-31-67 from the midportion of the N terminus, with natriuretic properties similar to ANF, contribute to the natriuretic response to NI, implying a physiologic role for these atrial peptides in modulating volume homeostasis in humans.     

Circulating immunoreactive proANP1-30 and proANP31-67 responses to acute exercise

The circulating immunoreactive atrial natriuretic peptide (C-terminal; alpha-ANP) increases during exercise to become suppressed in the first hours of the recovery. The response of the N-terminal ANP fragments to acute exercise is not known while proANP (31-67) appears to be elevated with chronic exercise. We evaluated the plasma concentrations of the N-terminal ANP fragments (1-30) and (31-67) in oarsmen (n=10) before and after two acute exercise bouts separated by 5 h. As control, measurements were made on a day with no exercise (n=12). At rest, the concentrations of proANP(1-30) and proANP(31-67) were 344+/-42 and 810+/-172 pmol x l(-1), respectively. Half an hour after the first exercise bout, proANP(1-30) was elevated (to 404+/-48 pmol x l(-1); P<0.05) and decreased below the pre-exercise level (to 316+/-41 pmol x l(-1); P<0.05) 4 h into the recovery period. Also, 30 min after the second exercise session, the concentration of proANP(1-30) was elevated to 408+/-45 pmol x l(-1) (P<0.05) and the pre-exercise level was re-established on the following morning. Thus, proANP(1-30), rather than proANP(31-67), responded to acute exercise. These results suggest that atrial distension and, therefore, the central blood volume changes markedly in athletes during a day with repeated exercise bouts.     

Processing of thyrotropin-releasing hormone prohormone (pro-TRH) generates pro-TRH-connecting peptides. Identification and characterization of prepro-TRH-(160-169) and prepro-TRH-(178-199) in the rat nervous system

Rat thyrotropin-releasing hormone prohormone (pro-TRH) contains five separate copies of the TRH progenitor sequence: Gln-His-Pro-Gly. Each of the five sequences is flanked by pairs of basic residues and linked together by one of several predicted connecting sequences. Two of the pro-TRH-connecting peptides, prepro-TRH-(160-169) and prepro-TRH-(178-199), were detected in extracts of rat neural tissues by radioimmunoassay using antibodies directed against the corresponding synthetic probes. Endogenous prepro-TRH-(160-169) and prepro-TRH-(178-199) were purified by gel exclusion chromatography, reverse-phase high pressure liquid chromatography, and ion-exchange chromatography. Structural identification of each peptide was achieved by chromatographic comparison with synthetic standards, immunological analysis, and tryptic mapping. Equimolar amounts of these connecting fragments were observed in hypothalamus and spinal cord. Quantification of TRH in spinal cord and hypothalamus extracts revealed the presence of 4.9-6.3 mol of TRH/mol of prepro-TRH-(178-199) and 4.4-6 mol of TRH/mol of prepro-TRH-(160-169), respectively. By using the indirect immunofluorescence technique, prepro-TRH-(178-199) immunoreactive cell bodies were found in the paraventricular nucleus of the hypothalamus, and a dense plexus of immunopositive nerve terminals was observed in the external zone of the median eminence, in a distribution similar to that described for TRH. These studies demonstrate that prepro-TRH-(160-169) and prepro-TRH-(178-199) are, together with TRH, predominant storage forms of the TRH precursor in hypothalamus and spinal cord, being present in molar ratios corresponding to those expected for a nearly complete processing of the prohormone molecule. The presence of pro-TRH-connecting peptides in various brain regions, including the median eminence, suggests that these peptides might act as neuromodulators in the central nervous system and/or neuroendocrine signals at the pituitary level. In the olfactory lobes, prepro-TRH is processed differently since a C-terminally extended form of TRH, prepro-TRH-(172-199), is found as a major end product along with lower but significant amounts of prepro-TRH-(178-199) and prepro-TRH-(160-169). The striking difference in pro-TRH processing patterns among the various tissues examined suggests differential regulating mechanisms for TRH and/or TRH-related activities.     

Application of the multiple antigenic peptides (MAP) strategy to the production of prophormone convertases antibodies: Synthesis,characterization and use of 8-branched immunogenic peptides

Antiserum against an N-terminal sequence of murine prohormone convertase-1 (mPC1) incorporating the sequence immediatley following the junction between the putative pro-region and the active enzyme was obtained. This was accomplished using the multiple antigenic peptide (MAP) approach whereupon an 8-branched polylysine core to which are grafted multiple copies of a 16 amino acid peptide representing the N-terminal sequence of mPC1 (positions 84–99) was synthesized by solid-phase Fmoc chemistry. The ensuing peptide was purified and fully characterized by RP-HPLC, ¹H-NMR, amino acid composition, peptide sequencing and ion-spray mass spectrometry. The immunological properties of the resulting antibodies in detecting recombinant PC1 in both crude and purified preparations were compared with antibodies raised against a similar N-terminal segment of PC1 but using the conventioanl method of peptide–carrier protein conjugation and also developed against a C-terminal fusion protein of PC1. Our data indicate that the MAP antibody was as efficient as both the amino and carboxy-terminal antibodies in qualitative as well as quantitative analysis of PC1 encoded protein by radioimmunoassay. Following an identical approach, antibodies against other prohormone convertases like furin, PC5/6 and PACE4 were also developed and subsequently applied to a number of biochemical and immunological studies. In each case, the ease of preparation and high immunogenicity of the MAP approach were confirmed and reside in the simplicity and rapidity with which a potent and useful antiserum is obtained.     

Atrial natriuretic factor in human plasma

A reproducible and sensitive radioimmunoassay (RIA) was developed to measure ANF in human plasma. Immunoreactive ANF was extracted from plasma with Sep-Pak cartridges, using 0.2% ammonium acetate (pH 4) with acetonitrile. The sensitivity of the assay was 3.9 pg/ml. The coefficient of variance for inter-assay and intra-assay was 16.8% and 6.8%, respectively. In normal healthy subjects (n = 67), ANF content was 11.9 +/- 1.3 pg/ml (mean +/- SEM). Significantly-higher ANF concentrations were found in proximal coronary sinus blood, being 6 to 37 times greater than in the peripheral circulation. Comparison of the prior extraction method with direct RIA revealed a good correlation (r = 91) in samples containing higher than 100 pg/ml ANF. No correlation was observed with lower values. The elution profiles of reverse-phase HPLC of peripheral and coronary sinus plasma extracts were similar but somewhat complex, with the main immunoreactive peak corresponding to a low-molecular-weight peptide.     

Role of atrial natriuretic peptide in systemic responses to acute isotonic volume expansion.

Atrial natriuretic peptide (ANP) may activate multiple mechanisms that protect against circulatory volume overload. We hypothesized that a temporal relationship exists between increases in cardiac filling pressure and plasma ANP concentration and also between ANP elevation and vasodilation, fluid movement from plasma to interstitium, and increased urine volume (UV). We infused 30 ml/kg isotonic saline at 100 ml/min in seven supine male subjects and monitored responses for 3 h postinfusion. Right atrial pressure (RAP) was measured via a central catheter. ANP (pmol/l) was measured by radioimmunoassay. Transcapillary fluid transport (TFT) equaled infused volume minus UV, insensible fluid loss, and change in plasma volume (PV, measured with Evan's blue). Systemic vascular resistance (SVR) was calculated as (mean arterial pressure-RAP)/cardiac output (determined by acetylene rebreathing). Plasma oncotic pressure (OP) was measured directly. During infusion, mean TFT (+/- SE) increased from net reabsorption during control of 111 +/- 27 ml/h to net filtration of 1,219 +/- 143 ml/h (P < 0.01). At end infusion, mean RAP, heart rate, and PV exhibited peak increases of 146, 23, and 27%, respectively. Concurrently, SVR and OP achieved nadirs 29 and 31% below control, respectively. Mean plasma ANP and UV peaked (45 and 390%, respectively) at 30 min postinfusion. Systemic vasodilation and capillary filtration resulted from and compensated for infusion-induced circulatory pressure increases and hemodilution. By 1 h postinfusion, most cardiovascular variables had returned toward control levels, and net reabsorption of extravascular fluid ensued.(ABSTRACT TRUNCATED AT 250 WORDS)     

Protection of mice and nude rats against toxoplasmosis by a multiple antigenic peptide construction derived from Toxoplasma gondii P30 antigen.

The first part of this work presents the sequence of the first 20 NH2 terminus residues obtained from P30, the major surface Ag of Toxoplasma gondii, purified by HPLC. A synthetic peptide (P30 48-67) has been prepared both in linear form and as a multiple antigenic peptide (MAP) construct. Immunization of mice and rats with the P30 48-67 MAP in the presence of IFA induces high levels of IgG antibodies that recognize both the linear peptide and the MAP construct in ELISA, and P30 in Western blots of NP-40-extracted tachyzoite Ag. Because these sera are negative in immunofluorescence assays with whole tachyzoites, it seems that IgG antibodies induced by P30 48-67 MAP, although recognizing the denatured structure, are unable to recognize the native protein. However, the protective effect of both constructs has then been studied in mice and nude rats. Whereas immunization of mice with the monomeric peptide does not confer any protection against oral infection with 1200 cysts of T. gondii 76K strain (mortality within 11 days), 40% of mice immunized with the MAP construct survived up to 75 days after infection. Nude rats were passively transferred with 5 x 10(4) T lymphocytes from P30 48-67 MAP-immunized Fischer rats before infection with 5 x 10(4) RH strain tachyzoites. They survived up to 40 days after infection and raised an intense IgG antibody response against P30, whereas nude rats transferred with control lymphocytes died within 21 days. This shows that immunization with P30 48-67 MAP also induces an efficient T cell immune response. The present work confirms the recently demonstrated role of P30 in protective immunity and shows the interest of peptide octameric constructions as inducers of partially protective immune responses in toxoplasmosis, as already demonstrated in schistosomiasis.