Ghrelin Amplifies Dopamine Signaling by Cross Talk Involving Formation of Growth Hormone Secretagogue Receptor/Dopamine Receptor Subtype 1 Heterodimers

Our objective is to determine the neuromodulatory role of ghrelin in the brain. To identify neurons that express the ghrelin receptor [GH secretagogue receptor (GHS-R)], we generated GHS-R-IRES-tauGFP mice by gene targeting. Neurons expressing the GHS-R exhibit green fluorescence and are clearly evident in the hypothalamus, hippocampus, cortex, and midbrain. Using immunohistochemistry in combination with green fluorescent protein fluorescence, we identified neurons that coexpress the dopamine receptor subtype 1 (D1R) and GHS-R. The potential physiological relevance of coexpression of these two receptors and the direct effect of ghrelin on dopamine signaling was investigated in vitro. Activation of GHS-R by ghrelin amplifies dopamine/D1R-induced cAMP accumulation. Intriguingly, amplification involves a switch in G protein coupling of the GHS-R from Gα11/q to Gαi/o by a mechanism consistent with agonist-dependent formation of GHS-R/D1R heterodimers. Most importantly, these results indicate that ghrelin has the potential to amplify dopamine signaling selectively in neurons that coexpress D1R and GHS-R.

Activation of rho through a cross-link with polyamines catalyzed by Bordetella dermonecrotizing toxin

The small GTPase Rho, which regulates a variety of cell functions, also serves as a specific substrate for bacterial toxins. Here we demonstrate that Bordetella dermonecrotizing toxin (DNT) catalyzes cross-linking of Rho with ubiquitous polyamines such as putrescine, spermidine and spermine. Mass spectrometric analyses revealed that the cross-link occurred at Gln63, which had been reported to be deamidated by DNT in the absence of polyamines. Rac1 and Cdc42, other members of the Rho family GTPases, were also polyaminated by DNT. The polyamination, like the deamidation, markedly reduced the GTPase activity of Rho without affecting its GTP-binding activity, indicating that polyaminated Rho behaves as a constitutively active analog. Moreover, polyamine-linked Rho, even in the GDP-bound form, associated more effectively with its effector ROCK than deamidated Rho in the GTP-bound form and, when microinjected into cells, induced the anomalous formation of stress fibers indistinguishable from those seen in DNT-treated cells. The results imply that the polyamine-linked Rho, transducing signals to downstream ROCK in a novel GTP-independent manner, plays an important role in DNT cell toxicity.

Molecular endocrinology and physiology of the aging central nervous system

Aging is associated with a progressive decline in physical and cognitive functions. The impact of age-dependent endocrine changes regulated by the central nervous system on the dynamics of neuronal behavior, neurodegeneration, cognition, biological rhythms, sexual behavior, and metabolism are reviewed. We also briefly review how functional deficits associated with increases in glucocorticoids and cytokines and declining production of sex steroids, GH, and IGF are likely exacerbated by age-dependent molecular misreading and alterations in components of signal transduction pathways and transcription factors.

Children with in utero cocaine exposure do not differ from control subjects on intelligence testing

OBJECTIVE

To determine if in utero cocaine exposure affects IQ scores in children at age 4 years.

DESIGN

A prospective, longitudinal evaluation by blinded examiners of the IQ scores of cocaine-exposed and control children of low socioeconomic status who have been observed since birth.

SETTING

A study center in an inner-city hospital.

PARTICIPANTS

One hundred one children with in utero cocaine exposure and 118 control children, all of whom were 34 weeks' gestational age or older and nonasphyxiated at birth.

MAIN OUTCOME MEASURE

Intelligence quotient scores on a standardized intelligence test, the Wechsler preschool and Primary Scale of Intelligence--Revised.

RESULTS

Seventy-one cocaine-exposed and 78 control children were administered the Wechsler Preschool and Primary Scale of Intelligence--Revised. Maternal, natal, and 30-month characteristics of the children tested did not differ from those not tested. Groups did not differ on mean Performance (83.2 vs 87.0), Verbal (79.0 vs 80.8), or Full Scale (79.0 vs 81.9) IQ scores (all P > or = .10 [values for cocaine-exposed children given first]). None of these 3 scores was associated with cocaine exposure in multivariate linear regressions. Although cocaine-exposed and control groups did not differ in outcome, 93% of cocaine-exposed and 96% of control children had Full Scale IQ scores below 100, the mean IQ score for the test.

CONCLUSIONS

In an inner-city cohort, IQ scores did not differ between cocaine-exposed and control children. However, both groups performed poorly.

Primary structure of two cytolysin isoforms from Stichodactyla helianthus differing in their hemolytic activity

Sticholysin I (St-I) and sticholysin II (St-II) are cytolysins purified from the sea anemone Stichodactyla helianthus with a high degree of sequence identity (93%) but clearly differenced in their hemolytic activity. In order to go further into the structural determinants for the different behavior of St-I and St-II, we report here the complete amino acid sequences and the consensus secondary structure prediction of both proteins. The complete determination of St-II primary structure confirms the partial revision of cytolysin III amino acid sequence. All nonconservative changes between St-I and St-II are located at the N-terminal. According to our prediction these changes could be located at the same face of an alpha-helix during pore formation events and could account for the observed differences in hemolytic activity between St-I and St-II.

Automated interpretation of low-energy collision-induced dissociation spectra by SeqMS, a software aid for de novo sequencing by tandem mass spectrometry

SeqMS, a software aid for de novo sequencing by tandem mass spectrometry (MS/MS), which was initially developed for the automated interpretation of high-energy collision-induced dissociation (CID) MS/MS spectra of peptides, has been applied to the interpretation of low-energy CID and post-source decay (PSD) spectra of peptides. Based on peptide backbone fragmented ions and their related ions, which are the dominant ions observed in the latter two techniques, the types of ions and their propensities to be observed have been optimized for efficient interpretation of the spectra. In a typical example, the modified SeqMS allowed the complete sequencing of a 31-amino acid synthetic peptide, except for the isobaric amino acids (Leu or Ile, and Lys or Gln), based on only the low-energy CID-MS/MS spectrum.

Differentiating alpha- and beta-aspartic acids by electrospray ionization and low-energy tandem mass spectrometry

Spectra obtained by low-energy electrospray ionization tandem mass spectrometry (ESI-MS/MS) of 34 peptides containing aspartic acids at position n were studied and unambiguously differentiated. beta-Aspartic acid yields an internal rearrangement similar to that of the C-terminal rearrangements of protonated and cationized peptides. As a result of this rearrangement, two different ions containing the N- and the C-terminal ends of the original peptide are formed, namely, the bn-1 + H2O and y"l - n + 1 - 46 ions, respectively, where e is the number of amino acid residues in the peptide. The structure suggested for the y"l - n + 1 - 46 ion is identical to that proposed for the vn ions observed upon high-energy collision-induced dissociation (CID) experiments. The intensity of these ions in the low-energy MS/MS spectra is greatly influenced by the presence and position of basic amino acids within the sequences. Peptides with a basic amino acid residue at position n - 1 with respect to the beta-aspartic acid yield very intense bn-1 + H2O ions, while the y"l - n + 1 - 46 ion was observed mostly in tryptic peptides. Comparison between the high- and low-energy MS/MS spectra of several isopeptides suggests that a metastable fragmentation process is the main contributor to this rearrangement, whereas for long peptides (40 AA) CID plays a more important role. We also found that alpha-aspartic acid containing peptides yield the normal immonium ion at 88 Da, while peptides containing beta-aspartic acid yield an ion at m/z 70, and a mechanism to explain this phenomenon is proposed. Derivatizing isopeptides to form quaternary amines, and performing MS/MS on the sodium adducts of isopeptides, both improve the relative intensity of the bn + 1 + H2O ions. Based on the above findings, it was possible to determine the isomerization sites of two aged recombinant growth proteins.

A prospective evaluation of early language development in children with in utero cocaine exposure and in control subjects

A cohort of children of low socioeconomic status, 76 with in utero cocaine exposure and 81 control subjects, was assessed for early language development at 2 1/2 years of age by a masked examiner using the Preschool Language Scale. There were no differences between groups in expressive, receptive, or total language score (all p > or = 0.57). Physicians caring for cocaine-exposed children with early language delay should not automatically ascribe the delay to cocaine exposure but should initiate a standard evaluation for language delay.

Automated interpretation of high-energy collision-induced dissociation spectra of singly protonated peptides by 'SeqMS', a software aid for de novo sequencing by tandem mass spectrometry

SeqMS, a software program designed for the automated interpretation of high-energy collision-induced dissociation (CID) mass spectra of singly protonated peptides ionized by fast atom bombardment, has been developed. The software is capable of probing the sequence of an unknown peptide, and even of certain modified peptides. The program, compiled for WINDOWS95 or NT, also permits the retrieval of raw data and the reconstruction of the spectra on a user-friendly graphical interface with the aid of several tools for processing the spectra, which include setting multiple threshold levels and automatic peak detection. SeqMS is capable of generating candidate sequences, based on the detected peaks, and of displaying the resulting assignments for each candidate in a spectrum or in tabular form. The software has the following capabilities: 1) the ions derived from backbone and side-chain fragmentations, internal and immonium ions, and side-chain loss ions can be used for calculation; 2) 18O-labeling of a peptide at the C terminus, a methodology which was developed to differentiate N-terminal from C-terminal ions, is applicable as an optional setting; 3) modified amino acids and N- or C-terminal blocking groups are taken into account for calculation according to the user's setting in a library; 4) amino acid composition and partial or complete amino acid sequence of a peptide can be used as input for calculation; 5) the assignments of signal output in a spectrum can be graphically edited, and then re-calculated based on the edited peaks. The efficacy of the program is demonstrated by testing 74 high-energy CID spectra, obtained using a four-sector instrument, of synthetic, proteolytic, and biologically active peptides, some of which contain modified groups.

Growth hormone secretagogues: prospects and potential pitfalls

The growth hormone secretagogues (GHSs) are the first well-characterised agents that rejuvenate the growth hormone (GH)/insulin-like growth factor (IGF-1) axis. This property was discovered during investigations of the underlying causative mechanisms of age-related endocrine changes. Chronic administration of the long acting GHS, MK-0677, reverses the age-related decline in pulse-amplitude of GH secretion and restores IGF-1 levels producing profiles typical of young adults. This restoration is accompanied by improvements in body composition in frail elderly subjects. When given acutely, the GHSs also increase appetite. Following cloning and characterisation of the GHS-receptor (GHS-R) an endogenous ligand, ghrelin, was isolated and identified. Ghrelin shares the GH releasing and orexigenic properties of the GHSs. Studies using Ghsr-null mice confirmed that the GHS-R was the ghrelin-receptor; hence, the GHSs should be considered to be 'ghrelin mimetics.' Ghrelin levels are reported to decline during ageing, therefore long-acting GHSs are ideal candidates for ghrelin replacement therapy.

Impact of distinct therapies on antibody response to SARS-CoV-2 vaccine in systemic lupus erythematosus

Objective

To date, the only study that has assessed the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2 mRNA) vaccine in systemic lupus erythematosus (SLE) observed a moderate response, but the sample size precluded an accurate analysis of the effect of individual drugs. Therefore, we evaluated the immunogenicity of an inactivated SARS‐CoV‐2 vaccine (Sinovac‐CoronaVac) and the influence of different medications in SLE. Safety was also assessed.

Methods

We conducted a prospective controlled study of 232 SARS‐CoV‐2–naive SLE patients and 58 SARS‐CoV‐2–naive controls who were vaccinated with 2 doses of Sinovac‐CoronaVac with a 28‐day interval (day 0/day 28 [D0/D28]). Immunogenicity analysis at D0/D28 and D69 included anti‐SARS‐CoV‐2 S1/S2 IgG seroconversion (SC) and neutralizing antibodies (NAb) positivity. The influence of individual drugs on immune response and safety was assessed.

Results

Patients and controls were well balanced for age (P = 0.771). At D69, SLE patients showed a moderate SC (70.2% versus 98.1%; P < 0.001) and moderate frequency of NAb positivity (61.5% versus 84.6%; P = 0.002), although both frequencies were lower than in controls. Factors associated with lower SC in univariate analysis at D69 were prednisone use (odds ratio [OR] 0.215 [95% confidence interval (95% CI) 0.108–0.427], P < 0.001) and mycophenolate mofetil (MMF) use (OR 0.201 [95% CI 0.107–0.378], P < 0.001), whereas hydroxychloroquine (HCQ) use led to a 2.5 increase in SC (P = 0.011). SLE patients who were receiving HCQ monotherapy had similar SC to controls at D69 (100% versus 98.1%; P = 1.000). In multivariate analysis, prednisone and MMF use were independently associated with lower SC (P < 0.001) and NAb positivity (P < 0.001). Safety analysis revealed no moderate/severe adverse events.

Conclusion

Sinovac‐CoronaVac has a moderate immunogenicity in SARS‐CoV‐2–naive SLE patients with an excellent safety profile. We further demonstrate that HCQ may improve SC, whereas prednisone and MMF had a major deleterious effect in vaccine response, reinforcing the need to investigate the role of temporary MMF withdrawal or a vaccine‐booster dose (ClinicalTrials.gov identifier: NCT04754698).

Levansucrase from Acetobacter diazotrophicus SRT4 is secreted via periplasm by a signal-peptide-dependent pathway

Acetobacter diazotrophicus SRT4 secretes a constitutive levansucrase (LsdA) (EC 2.4.1.10) that is responsible for sucrose utilization. Immunogold electron microscopical studies revealed that LsdA accumulates in the periplasm before secretion. The periplasmic and extracellular forms of the enzyme were purified to homogeneity. Both proteins exhibited similar physical and biochemical characteristics indicating that LsdA adopts its final conformation in the periplasm. The N-terminal sequence of mature LsdA was pGlu-Gly-Asn-Phe-Ser-Arg as determined by PSD-MALDI-TOFMS (post-source decay-matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry). Comparison of this sequence with the predicted precursor protein revealed the cleavage of a 30-residue typical signal peptide followed by the formation of the pyroglutamic acid (pGlu) residue. Thus, in contrast with other Gram-negative bacteria, A. diazotrophicus secretes levansucrase by a signal-peptide-dependent mechanism.

Play behavior in toddlers with in utero cocaine exposure: a prospective, masked, controlled study

Play behavior was compared between toddlers with in utero cocaine exposure and controls of similar low socioeconomic status enrolled at birth in a prospective, masked study. At 18 and 24 months, 83 cocaine-exposed and 93 control toddlers were videotaped playing on their own for 15 minutes. An observer who was off-site and unaware of project purpose or drug exposure status of toddlers recorded the most cognitively complex play activity per 15-second interval. In a total of 315 play sessions, the groups did not differ in middle and highest level of play achieved at either 18 or 24 months (p > or = .27). After controlling for confounders, the proportions of play behavior in each of six play categories were similar in the two groups at both 18 and 24 months (p > or = .42). We conclude that in utero cocaine exposure was not associated with differences in play behavior in this cohort of cocaine-exposed and control toddlers.

Problem-solving ability of inner-city children with and without in utero cocaine exposure

To evaluate the problem-solving abilities of a cohort of inner-city cocaine-exposed children and controls, children were invited to play with the Goodman Lock Box, a large red and blue box with 10 compartments, each having a different lock and toy. Examiners, blinded to the children's group status, coded the children's activities during the 6.5-minute play period. Nineteen behaviors were collapsed into three outcomes: Aimless Actions, Competence, and Mental Organization. Groups' scores were compared with scores of the Goodman standardization sample of mixed socioeconomic status preschoolers. Seventy-three cocaine-exposed children and 82 controls were evaluated at age 3.5 years; of these, 58 cocaine-exposed and 63 controls were reevaluated at age 4.5 years. The groups' scores did not differ on any outcome at either time point (p > or = .22). However, both groups' Mental Organization scores were consistently lower than the Goodman group at each age (p < .01). This high-risk cohort may experience problems functioning in more complex environments such as the classroom.

Increment of immunogenicity after third dose of a homologous inactivated SARS-CoV-2 vaccine in a large population of patients with autoimmune rheumatic diseases

Objective

To determine the immunogenicity of the third dose of CoronaVac vaccine in a large population of patients with autoimmune rheumatic diseases (ARD) and the factors associated with impaired response.

Methods

Adult patients with ARD and age-balanced/sex-balanced controls (control group, CG) previously vaccinated with two doses of CoronaVac received the third dose at D210 (6 months after the second dose). The presence of anti-SARS-CoV-2 S1/S2 IgG and neutralising antibodies (NAb) was evaluated previously to vaccination (D210) and 30 days later (D240). Patients with controlled disease suspended mycophenolate mofetil (MMF) for 7 days or methotrexate (MTX) for 2 weekly doses after vaccination.

Results

ARD (n=597) and CG (n=199) had comparable age (p=0.943). Anti-S1/S2 IgG seropositivity rates significantly increased from D210 (60%) to D240 (93%) (p<0.0001) in patients with ARD. NAb positivity also increased: 38% (D210) vs 81.4% (D240) (p<0.0001). The same pattern was observed for CG, with significantly higher frequencies for both parameters at D240 (p<0.05). Multivariate logistic regression analyses in the ARD group revealed that older age (OR=0.98, 95% CI 0.96 to 1.0, p=0.024), vasculitis diagnosis (OR=0.24, 95% CI 0.11 to 0.53, p<0.001), prednisone ≥5 mg/day (OR=0.46, 95% CI 0.27 to 0.77, p=0.003), MMF (OR=0.30, 95% CI 0.15 to 0.61, p<0.001) and biologics (OR=0.27, 95% CI 0.16 to 0.46, p<0.001) were associated with reduced anti-S1/S2 IgG positivity. Similar analyses demonstrated that prednisone ≥5 mg/day (OR=0.63, 95% CI 0.44 to 0.90, p=0.011), abatacept (OR=0.39, 95% CI 0.20 to 0.74, p=0.004), belimumab (OR=0.29, 95% CI 0.13 to 0.67, p=0.004) and rituximab (OR=0.11, 95% CI 0.04 to 0.30, p<0.001) were negatively associated with NAb positivity. Further evaluation of COVID-19 seronegative ARD at D210 demonstrated prominent increases in positivity rates at D240 for anti-S1/S2 IgG (80.5%) and NAb (59.1%) (p<0.0001).

Conclusions

We provide novel data on a robust response to the third dose of CoronaVac in patients with ARD, even in those with prevaccination COVID-19 seronegative status. Drugs implicated in reducing immunogenicity after the regular two-dose regimen were associated with non-responsiveness after the third dose, except for MTX.

Trial registration numberNCT04754698.

Potassium (K+) channel expression in basal forebrain cholinergic neurons

Basal forebrain cholinergic neurons (BFCN) are depleted early in the course of Alzheimer's disease (AD). BFCN voltage-gated K(+) channels regulate acetylcholine release and may play a role in BFCN neurodegeneration. Neuronal voltage-gated K(+) channels are heterotetrameric assemblies of K(v) and accessory subunits. Currently, there is no available information about the K(v) proteins expressed in BFCN. Immunohistochemical techniques were used to investigate the expression of specific K(v) subunits in rat brain BFCN. Our results showed that BFCN express both K(v)3.1 and K(v)2.1 subunits. However, the K(v)2.1 subunit showed a wider distribution in noncholinergic neurons than the K(v)3.1 subunit. K(v)3.1 and K(v)2.1 immunostaining was noticeable not only in neuronal cell bodies but also in the dendritic ramifications of these neurons. Insofar as the K(v)3.1 subunit has been classically associated with "fast-spiking neurons" and BFCN have low firing rates and long-duration action potentials, K(v)3.1 subunits may have functions other than facilitating high-frequency firing in BFCN.

Effects of circuit resistance training and timely protein supplementation on exercise-induced fat oxidation in tetraplegic adults

BACKGROUND

Substrate utilization during exercise in persons with spinal cord injury (SCI) remains poorly defined.

PURPOSE

To investigate effects of circuit resistance training (CRT) and timing of protein supplementation (PS) on fuel utilization in persons with tetraplegia.

METHODS

Eleven individuals with chronic tetraplegia underwent 6 months of CRT 3 times weekly. Five randomly assigned participants received immediate PS (iPS) administered in split doses prior to and following all exercise sessions. Other participants consumed a matched dose of PS that was delayed until 24 hours post-exercise (dPS). Participants underwent a maximal graded exercise test (GXT) to volitional exhaustion at 4 conditioning time points: 3 months before (-3mo), at the beginning of (0mo), 3 months into (3mo), and 6 months following (6mo) the CRT conditioning program. Respiratory measures were continuously obtained throughout the GXT via open-circuit spirometry. Fuel utilization and energy expenditure were computed from the respiratory data.

RESULTS

The differences in changes in substrate utilization between the PS groups were not significant as determined by the interaction of PS group and conditioning time point, F (3, 27) = 2.32, P = .098, η(2) P = .205. Maximal absolute fat oxidation did not change significantly from 0 to 6mo (mean difference, 0.014 ± 0.031 g/min; P = .170), and fat oxidation remained low never exceeding an average of 0.10 ± 0.09 g/min for any given exercise intensity.

CONCLUSION

Maximum fat utilization during exercise and fat utilization at matched exercise intensities were not increased in persons with tetraplegia, independent of PS, and levels of fat oxidation remained low after training.

Selective isolation and identification of N-terminal blocked peptides from tryptic protein digests

A method for the easy isolation and direct sequencing of N-terminally blocked peptide in proteins refractory to N-terminal sequencing was developed. It is based essentially on tandem enzymatic treatments of the protein with trypsin and carboxypeptidase B, and selective isolation of the Nalpha-blocked peptide using ion-exchange chromatography. The chromatographic step was optimized for picomole amounts of sample and very short elution times by placing a thin layer of the resin over the membrane of an ultrafiltration tube. The isolated fraction can be analyzed directly using MALDI or ESI mass spectrometry. The method was applied to several recombinant and natural N-terminal acetylated proteins. A critical discussion on the intrinsic limitations of the method is also given.

Hemodynamic changes with enalapril in pulmonary arterial hypertension secondary to congenital heart disease

Enalapril was used to treat five patients with pulmonary arterial hypertension secondary to congenital cardiopathy, three with ventricular septal defect, one with arterial septal defect, and one with patent ductus arteriosus. The dose of enalapril was 20 mg/day. All patients underwent pretreatment and posttreatment cardiac catheterization. It was concluded that enalapril may be a useful drug in the treatment of pulmonary arterial hypertension secondary to congenital cardiopathy.

Structural characterization of Acetobacter diazotropicus levansucrase by matrix-assisted laser desorption/ionization mass spectrometry: identification of an N-terminal blocking group and a free-thiol cysteine residue

High-resolution matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to characterize the primary structure of the levansucrase (EC 2.4.1.10) secreted by Acetobacter diazotropicus SRT4. The technique permitted not only the reading frame of this enzyme, the amino acid sequence of which was deduced from DNA, but also the elucidation of an N-terminal blocking group and the position of a disulfide bridge between Cys309 and Cys365 among the three Cys residues. A free cysteine (Cys127) was identified by modifying an intact molecule with a sulfhydryl reagent, 5-(octyldithio)-2-nitrobenzoic acid, under non-reducing conditions. In addition, the enzyme obtained by site-directed mutagenesis at Asp279 to Asn279 was also identified by the above methods. Post-source decay analysis of the tryptic peptide containing the mutation site unequivocally revealed an Asn residue at position 279.

Cocaine-exposed children: follow-up through 30 months

This prospective, blinded study evaluates the effect of in utero cocaine exposure on outcome of nonasphyxiated, term and near-term children born to women of low socioeconomic status. Two hundred nineteen children (101 cocaine-exposed and 118 control) with extensive natal evaluations are evaluated at 6-month intervals. We report here growth, performance on the Bayley Scales of Infant Development (BSID) through 30 months of age, and tone and reflexes at 6 and 12 months. To date, subjects have had 816 follow-up visits, with subject retention greater than or equal to 73%. Cocaine-exposed children showed statistically lower mean weights and smaller mean head circumferences than control children over the 30-month follow-up period (p < or = .011). The percentage of children with abnormal tone and reflexes, however, was similar in the two groups at 6 and 12 months (p > or = .34). Mean BSID Mental Development Index (MDI) and Psychomotor Development Index scores did not differ between the two groups (p > or = .16), although both groups' scores decreased over time (p < .001). Of concern, both cocaine-exposed and control groups had lower mean MDI scores than those published for a group of children of higher socioeconomic status. We conclude that, in our cohort of children, low socioeconomic or minority status may have had a substantial influence on BSID scores whereas in utero drug exposure did not.

[Use of enalapril, an angiotensin-converting enzyme inhibitor, in pulmonary artery hypertension]

Enalapril (E) was used to treat 16 patients with pulmonary arterial hypertension, 6 primary and 10 secondary, 5 of the latter with congenital heart disease and 5 with chronic obstructive pulmonary disease. The average dose of E was 20 mg/day. All patients underwent pre and post-treatment cardiac catheterization with determination of pressures at: right atrial (RA), main pulmonary artery (MPA), pulmonary capillary wedge pressure ( VCP) and systemic arterial (SA). Resistances forces were also measured as; total pulmonary (TPR), pulmonary arteriolar (PAR) and total systemic (TSR) as well as cardiac output (CO), and echo and electrocardiograms, chest x ray, stress test and respiratory function test. The functional class (NYHA) improved in all (p less than 0.001). The initial mean pressures were: RA 12.24 +/- 4.35; MPA 73.81 +/- 25.16; VCP 12 +/- 2.73 and SA 89 +/- 14; TPR 1477 +/- 761; PAR 1243 +/- 730 and TSR 1684 +/- 505.5; CO 4.5 +/- 1.29. The final values were: RA 9.66 +/- 2.46 (p less than 0.001); MPA 63.26 +/- 24.45 (p less than 0.001); VCP 11.33 +/- 2.38 (p = NS); SA 81 +/- 10 (p less than 0.001); TPR 1009.5 +/- 536.7 (p less than 0.001); PAR 829 +/- 511.5 (p less than 0.001); TSR 1309.6 +/- 296.3 (p less than 0.001); CO 5.2 +/- 1.44 (p less than 0.001). The average of minutes on treadmill was initially 8.2 +/- 2.45 and final 12.46 +/- 3.0 (p less than 0.001). It is concluded that enalapril is a useful drug in the treatment of pulmonary arterial hypertension of any etiology.