Angiotensin, bradykinin and the endothelium.

Angiotensins and kinins are endogenous peptides with diverse biological actions; as such, they represent current and future targets of therapeutic intervention. The field of angiotensin biology has changed significantly over the last 50 years. Our original understanding of the crucial role of angiotensin II in the regulation of vascular tone and electrolyte homeostasis has been expanded to include the discovery of new angiotensins, their important role in cardiovascular inflammation and the development of clinically useful synthesis inhibitors and receptor antagonists. While less applied progress has been achieved in the kinin field, there are continuous discoveries in bradykinin physiology and in the complexity of kinin interactions with other proteins. The present review focuses on mechanisms and interactions of angiotensins and kinins that deal specifically with vascular endothelium.

Pentoxifylline rescue preserves lung function in isolated canine lungs injured with phorbol myristate acetate.

OBJECTIVE: We hypothesized that pentoxifylline, administered after phorbol myristate acetate (PMA), would diminish the severity of lung injury. SETTING: Animal research laboratory. DESIGN: Comparative study. SUBJECTS: Mongrel dogs (n = 33). INTERVENTIONS: Baseline measurements were obtained from the isolated blood-perfused dog lung lobes after 1 h of stable perfusion and ventilation. Four different measures of lung compliance were obtained along with WBC and neutrophil counts. Pulmonary vascular resistance (PVR) and capillary filtration coefficient (Kf) were calculated, and the ratio of a normalized maximal enzymatic conversion rate to the Michaelis-Menten constant (Amax/Km) was used to assess perfused capillary surface area. The control lobes (n = 8) were ventilated and perfused for an additional 40 min while the injured lobes (n = 17) received PMA (0.1 microg/mL of perfusate). The pentoxifylline-protected lobes (n = 8) were treated with pentoxifylline (1 mg/mL of perfusate) 10 min after injury with PMA. All measurements were then repeated. MEASUREMENT AND MAIN RESULTS: The three groups did not differ significantly at baseline. The control lobes remained relatively stable over time. The injured lobes demonstrated marked deterioration in compliance: 8.79 +/- 0.7 to 5.97 +/- 0.59 mL/cm H(2)O (p < 0.05) vs 10.1 +/- 1.0 to 8.07 +/- 0.72 mL/cm H(2)O and 9.6 +/- 1.1 to 9.9 +/- 0.85 mL/cm H(2)O in the control and protected lobes, respectively. Both groups receiving PMA had similar drops in WBC and neutrophil counts, but the pentoxifylline-protected lobes had preservation of all four compliance measures. PVR increased from 37.8 +/- 1.8 to 118.6 +/- 12.7 cm H(2)O/L/min (p < 0.05) in the injured lobes vs 35.4 +/- 0.5 to 36.3 +/- 2.8 cm H(2)O/L/min and 40.4 +/- 0.04 to 46.7 +/- 2.8 cm H(2)O/L/min (p < 0.05) in the control and protected lobes, respectively. Kf increased < 25% in the protected group but more than tripled in the injured group. Amax/Km dropped from 559 +/- 36 to 441 +/- 33 mL/min (p < 0.05) in the injured lobes vs 507 +/- 14 to 490 +/- 17 mL/min and 609 +/- 34 to 616 +/- 37 mL/min in the control and pentoxifylline-protected lobes, respectively. CONCLUSIONS: The use of pentoxifylline as a rescue agent prevented the PMA-induced deterioration of lung compliance, vascular integrity, and endothelial metabolic function in this acute lung injury model, despite significant pulmonary neutrophil sequestration.

Vascular recruitment increases evidence of lung injury.

OBJECTIVE: Changes in pulmonary blood flow rate can alter the size of the perfused pulmonary capillary surface area. We tested the hypothesis that full recruitment of the pulmonary vascular bed may decrease evidence of lung injury by recruiting less injured capillaries. We also tested the hypothesis that endothelial ectoenzyme activity is an earlier indicator of lung injury than are permeability measures. DESIGN: Isolated canine lung lobes were perfused with autologous blood at constant blood flows of either 2.05+/-0.04 L/min (SEM) (high flow, full recruitment, n = 12) or 0.600 +/- 0.004 L/min (low flow, 33% full recruitment, n = 12) after lung injury to determine the effect of vascular recruitment on measures of injury. SETTING: Research laboratory at a medical university. SUBJECTS: Lung lobes were obtained from 36 mongrel dogs of either gender. INTERVENTIONS: Lung injury was induced by adding phorbol myristate acetate (PMA) to the blood perfusing the isolated lung. MEASUREMENTS AND MAIN RESULTS: Indicator dilution methods were used to measure single pass hydrolysis of 3[H]-benzoyl-Phe-Ala-Pro, a synthetic substrate for angiotensin converting enzyme, and calculate the modified first order kinetic parameter corresponding to the ratio of a normalized maximal enzymatic conversion rate (A(max)) to the Michaelis-Menten constant (K(m)), i.e., A(max)/K(m), before and after PMA. At a given flow rate, the decrease in A(max)/K(m)serves as an index of vascular injury. PMA decreased A(max)/K(m), percent metabolism, and fractional substrate utilization, and increased permeability, vascular resistance, and vascular pressures regardless of flow rate. The decrease in enzyme activity was detected earlier than the increase in permeability. CONCLUSION: The greater percentage decrease in percent metabolism and fractional substrate utilization and the earlier appearance of increased permeability during high flow indicates that increasing blood flow three-fold recruited injured vessels and/or increased vascular injury by increasing vascular perfusion pressures.

Ventilation above closing volume reduces pulmonary vascular resistance hysteresis.

The aim of this study was to determine the relationship of pulmonary vascular resistance (PVR) hysteresis and lung volume, with special attention to the effects of ventilation around closing volume (CV). Isolated, blood-perfused canine left lower lung lobes (LLL) were incrementally inflated and deflated. Airway and pulmonary artery pressures (PAP) were recorded after each stepwise volume change. Constant blood flow was provided (600 ml/min) and the pulmonary vein pressure (PVP) was held constant at 5 cm H2O. PAP changes, therefore, were a direct index of PVR changes. Group 1 lobes underwent a full inflation from complete collapse to total lobe capacity (TLC) followed by a full deflation. Group 2 lobes underwent two deflation/inflation cycles, after an initial full inflation. These cycles, both beginning at TLC, had deflation end above and below CV, respectively. Significant PVR hysteresis was noted when the first inflation and deflation were compared. The maximum difference in PAP on deflation was 3.3 cm H2O or 11%. The mean decrease was 2.7 cm H2O for 18 lobes (p < 0.0001). The PAPs on all subsequent inflations or deflations that began above CV remained 9% lower than the initial inflation (n = 9, p < 0.0001), but were not different from each other. However, the final inflation which began from below CV resulted in a 30% return of PVR hysteresis (mean increase in PAP of 0.8 cm H2O, n = 7, p < 0.004). We conclude that there is hysteresis in the PVR response during ventilation, with decreased PVR during deflation relative to the initial inflation, that this hysteresis is absent when lung volume is maintained greater than CV, and that hysteresis returns when inflation occurs after deflation below CV.

Measurement of pulmonary blood flow by fractal analysis of flow heterogeneity in isolated canine lungs.

Regional heterogeneity of lung blood flow can be measured by analyzing the relative dispersion (RD) of mass (weight)-flow data. Numerous studies have shown that pulmonary blood flow is fractal in nature, a phenomenon that can be characterized by the fractal dimension and the RD for the smallest realizable volume element (piece size). Although information exists for the applicability of fractal analysis to pulmonary blood flow in whole animal models, little is known in isolated organs. Therefore, the present study was done to determine the effect of blood flow rate on the distribution of pulmonary blood flow in the isolated blood-perfused canine lung lobe by using fractal analysis. Four different radiolabeled microspheres (141Ce, 95Nb, 85Sr, and 51Cr), each 15 microns in diameter, were injected into the pulmonary lobar artery of isolated canine lung lobes (n = 5) perfused at four different flow rates (flow 1 = 0.42 +/- 0.02 l/min; flow 2 = 1.12 +/- 0.07 l/min; flow 3 = 2.25 +/- 0.17 l/min; flow 4 = 2.59 +/- 0.17 l/min), and the pulmonary blood flow distribution was measured. The results of the present study indicate that under isogravimetric blood flow conditions, all regions of horizontally perfused isolated lung lobes received blood flow that was preferentially distributed to the most distal caudal regions of the lobe. Regional pulmonary blood flow in the isolated perfused canine lobe was heterogeneous and fractal in nature, as measured by the RD. As flow rates increased, fractal dimension values (averaging 1.22 +/- 0.08) remained constant, whereas RD decreased, reflecting more homogeneous blood flow distribution. At any given blood flow rate, high-flow areas of the lobe received a proportionally larger amount of regional flow, suggesting that the degree of pulmonary vascular recruitment may also be spatially related.

Effect of high blood flow on pulmonary vascular permeability to protein.

The elevated cardiac output associated with exercise increases lung lymph flow and may increase extravascular lung water. However, it is not known if extremely elevated cardiac output alters pulmonary vascular permeability. The hematocrit-protein method was used to determine the solvent drag reflection coefficient, an index of vascular permeability to proteins, in the isolated blood-perfused canine lung lobe. Microvascular pressure was obtained by double vascular occlusion. Lobes filtered fluid during perfusion at normal flow, 0.451 +/- 0.005 l/min (LF; n = 8), or high flow, 2.319 +/- 0.080 l/min (HF; n = 7). In the LF, venous pressure was elevated to 19.0 +/- 0.5 Torr to induce filtration, whereas Pv was 3.3 +/- 0.1 Torr in the HF. In HF vs. LF, respectively, arterial pressure was 61.4 +/- 7.1 vs. 28.0 +/- 1.0 Torr (P < 0.05), microvascular pressure was 31.9 +/- 3.0 vs. 22.2 +/- 0.9 Torr (P < 0.05), and sigma was 0.52 +/- 0.07 vs. 0.51 +/- 0.02 (P > 0.05). The fivefold increase in blood flow did not alter pulmonary vascular permeability to proteins; however, the capillary filtration coefficient was fivefold greater in the HF vs. LF group (0.328 +/- 0.059 vs. 0.067 +/- 0.007; P < 0.002). These data are compatible with enzyme activity measures indicating a direct linear relationship between blood flow rate and perfused pulmonary microvascular surface area. Although the data do not rule out the possibility of increased pulmonary vascular permeability to water during very elevated blood flow rates, the greater filtration rate during elevated flow is more likely related to increases in both microvascular pressure and surface area.

Infant deaths due to unintentional injury. An 11-year autopsy review.

OBJECTIVE: The number and causes of unintentional infant deaths were determined to identify common, preventable infant deaths. DESIGN: Retrospective autopsy review. SUBJECTS: Infants aged 1 day to 1 year undergoing complete autopsies. SETTING: Autopsies performed by the Louisville Office of the Kentucky Medical Examiner's Program from 1979 through 1989. METHOD: The manner of death was designated as an "accident" based on review of autopsy findings, scene investigation, and investigation by law enforcement officials. The cases were divided into groups based on the nature of the unintentional injury. RESULTS: Causes of death included asphyxia in mechanically unsafe sleeping environments, overlying, drowning, scald burns, plastic bag suffocation, house fires, motor vehicle collisions, aspiration of foreign bodies, hypothermia, blunt head trauma, and alcohol toxicity. The largest group of deaths in this series resulted from mechanically unsafe sleeping environments. CONCLUSIONS: The majority of deaths in this series could have been prevented by minor changes in the household environment. The causes of fatal unintentional injury to infants are different from those in older children. Pediatricians should be aware of hazards unique to this age group.

Cerebral tissue pulmonary embolization due to head trauma: a case report with immunohistochemical confirmation.

Pulmonary embolization of cerebral tissue as the result of severe head trauma is an uncommon, if not rare, phenomenon, and few cases have been reported in the literature. The authors discuss the case of a 51-year-old male who died six days after suffering extensive head trauma in a motor vehicle collision. At autopsy, white-gray emboli were found in several subsegmental pulmonary arteries. The results of histologic examination with the hematoxylineosin stain gave the impression that the emboli were necrotic cerebral tissue; however, routine special stains for neural tissue produced inconclusive results. Immunohistochemical staining of the emboli with monoclonal mouse anti-human neurofilament protein (Dako Corp., Carpinteria, California) confirmed the cerebral nature of the emboli. To the authors' knowledge, this is the first reported case of pulmonary embolization of cerebral tissue confirmed by immunohistochemistry.

Fetal death due to nonlethal maternal carbon monoxide poisoning.

Fetal death due to acute carbon monoxide poisoning is rarely reported in the medical literature. Of the eight cases found in literature review, only one documented the fetal carboxyhemoglobin concentration. This paper reports a fetal death due to accidental nonlethal maternal carbon monoxide intoxication in which both maternal and fetal carboxyhemoglobin concentrations were obtained. The corrected carboxyhemoglobin concentration was 61% at the time of death in utero, while the maternal carboxyhemoglobin was measured at 7% after one hour of supplemental oxygen. The authors review the mechanisms of fetal death and emphasize the different carbon monoxide kinetics in the fetal circulation.

Intestinal leucine aminopeptidase and alkaline phosphatase: genetic regulation and development in mice.

Intestinal and serum leucine aminopeptidase (LAP) and alkaline phosphatase (AKP) were characterized by electrophoresis for eight inbred strains of laboratory mice. Intestinal LAP and AKP of adult mice were expressed concordantly within strains, as banded or diffuse, and concordantly for rate of migration within strains that had diffuse isozymes. All strains, except DD/S, had a single band of serum LAP and a single, diffuse zone of serum AKP. DD/S had a double band of serum LAP as well as isozymes of intestinal LAP and AKP unlike those of other strains. All strains displayed similar, neuraminidase-sensitive isozymes of intestinal LAP and of AKP prior to weaning, but after weaning there was marked sensitivity to neuraminidase only in DD/S. In interstrain crosses, banded/diffuse, migration rate, and neuraminidase sensitivity were inherited as independent autosomal traits, with indications of variable penetrance and genetic interaction.

Increased resorption of embryos in O,O,S-trimethyl phosphorothioate-treated rats.

Pregnant rats (N = 7) were dosed p.o. with O,O,S-trimethyl phosphorothioate (OOS-TMP) (LD50 = 85) at 20 mg/kg on days G8 and G10. Seven animals were treated with corn oil and pair-fed. Five control animals were treated with corn oil. The abdomen was palpated on day G15 and in 4 animals out of 7 treated with OOS-TMP, complete resorption was observed. All pair-fed and control animals maintained pregnancy until day G21. Total number of resorption/number of implants was 60/95 (63.2%) in OOS-TMP animals, 21/82 (25.6%) in pair-fed animals and 4/65 (6.5%) in control animals. Incidence of complete resorption and % resorption were significantly higher (P less than 0.03 and P less than 0.01) in comparison with those in pair-fed animals. Fetuses from OOS-TMP mothers showed slight growth retardation. By skeletal examination, a missing vertebra and delayed ossifications were found in animals treated with OOS-TMP (20 mg/kg).

Delayed toxicity and delayed neurotoxicity of phosphonothioate and phosphonothioate esters.

The delayed neurotoxicity to hens and delayed toxicity to rats of the isomeric trimethyl phosphonothioates, trimethyl phosphate, and a series of the methyl and ethyl esters of methyl-, ethyl-, and phenylphosphonate and phosphonothioates were examined. All the O,O-dialkyl phosphonothioates, phosphorothioates, and their corresponding oxons were relatively nontoxic to rats, with oral LD50 values greater than the 150-450 mg/kg tested. The O,S-dialkyl phosphorothioate esters were highly acutely toxic. The rat acute LD50 values for O,S-dimethyl methylphosphonothioate and O,S-diethyl ethylphosphonothioate were 3 and 8 mg/kg. O,S-Diethyl ethylphosphonothioate and O,O, S-trimethyl phosphorothioate were the only compounds tested that showed delayed toxicity to rats. The delayed LD50 values for these two compounds were 7 and 15-20 mg/kg, respectively, with rats dying 3-22 d after treatment The delayed toxic effects were associated with continual loss of weight, reaching 18-46% at the time of death. Of this series of compounds, only O,O-diethyl phenylphosphonothioate and its oxon showed delayed neurotoxicity to hens 45 d after treatment. The minimum effective dose for these two compounds was 25 mg/kg.d administered ip for 10 d. These findings suggest that delayed neurotoxicity in hens is not due to the same mechanism as delayed toxicity in rats.