Hormone responses to stress in patients with major burns

Sex-specific issues of central and peripheral arginine-vasopressin concentrations in neurocritical care patients

BACKGROUND

Arginine-Vasopressin (AVP) is a nonapeptide that exerts multiple functions within the central nervous system and in the blood circulation that might contribute to outcome in critically ill patients. Sex differences have been found for mental and physical effects of AVP. For example, stress response and response due to hemorrhage differ between males and females, at least in animal studies. Data on humans -especially on AVP within the central nervous system (CNS)-are scarce, as cerebrospinal fluid (CSF) which is said to represent central AVP activity, has to be collected by means of invasive procedures. Here we present data on 30 neurocritical care patients where we simultaneously collected blood, CSF and saliva to analyze concentrations in the central and peripheral compartments.

PATIENTS AND METHODS

30 neurocritical care patients were included (13 male, 13 postmenopausal female, 4 premenopausal female) with a median age of 60 years. CSF, plasma and saliva were obtained simultaneously once in each patient and analyzed for AVP concentrations. Correlations between the central compartment represented by CSF, and the peripheral compartment represented by plasma and saliva, were identified. Relations between AVP concentrations and serum sodium and hematocrit were also determined.

RESULTS

In the whole patient collective, only very weak to weak correlations could be detected between AVP plasma/CSF, plasma/saliva and CSF/saliva as well as between AVP concentrations in each of the compartments and serum sodium/hematocrit. Regarding the subgroup of postmenopausal females, a significant moderate correlation could be detected for AVP in plasma and CSF and AVP CSF and serum sodium.

CONCLUSION

Absolute concentrations of AVP in central and peripheral compartments did not show sex differences. However, correlations between AVP plasma and CSF and AVP CSF and serum sodium in postmenopausal females indicate differences in AVP secretion and AVP response to triggers that deserve further examination.

Dose-response inhibitory effects of purified cathinone from khat (Catha edulis) on cortisol and prolactin release in vervet monkeys (Chlorocebus aethiops)

This study reports acute and sub-chronic effects of cathinone on hormonal alterations in single-caged vervet monkeys. Fourteen adult vervet monkeys were used, 12 of which were treated and 2 controls. Pre-treatment phase of 1 month aimed at establishing baseline levels of hormones while treatment phase of 4 months considered the dose- and time-response effects of cathinone on serum cortisol and prolactin levels. Test animals were allocated four groups of three animals each and administered 0.8, 1.6, 3.2 and 6.4 mg/kg body weight of cathinone orally while controls were administered normal saline. Treatment was done at alternate days of each week. Serum prolactin and cortisol immunoassays were done. Hormonal data was analysed by repeated measures ANCOVA. Results indicate a dose [F (4, 8) = 218, P < 0.001] and time [F (18, 142) = 21.7, P < 0.001] dependent effect of cathinone on cortisol levels with a significant dose by week interaction [F (71, 142) = 4.86, P < 0.001]. Similarly, there was a decrease in serum prolactin [F (4, 8) = 267, P < 0.001] with escalating doses of cathinone with a significant dose x week interaction [F (59, 118) = 13.03, P < 0.001]. The findings demonstrate that at high doses and long-term exposure, cathinone causes hormonal alterations probably via changes in hypothalamo-hypophyseo-adrenocortical and gonadal axes integrity.

The endocrine response to severe burn trauma

The endocrine system is frequently altered after a major burn trauma. Besides the endocrine response to stress characterized by hypercortisolism, several hypothalamus-hypophysis-target gland axes are rapidly perturbed within a few days. These alterations can persist in the long term and deserve an appropriate treatment. Disturbances in water clearance and glucidic metabolism are also common and need to be diagnosed and corrected to decrease morbidity in such patients. Bone and mineral metabolism is deeply compromised and requires correction of mineral abnormalities in order to improve symptoms and prevent bone loss. No large prospective and/or intervention trials are available to date to elaborate age-related, evidence-based recommendations to monitor and treat burn-related endocrine alterations.

Trimethoprim-induced hyperkalemia in burn patients treated with intravenous or oral trimethoprim sulfamethoxazole for methicillin-resistant Staphylococcus aureus and other infections: nature or nurture?

Trimethoprim is well known to cause rashes; however, what is not commonly known is that it causes sudden and profound hyperkalemia in 10 to 20% of treated patients. The uniqueness of burn patients begs the question whether changes known to occur in these patients might also increase this trimethoprim effect. After institutional review board approval, a retrospective study evaluated 224 patients with thermal injury who had been treated with trimethoprim sulfamethoxazole (TMP-SMX), 24 of whom had underlying renal impairment (creatinine clearances <50 ml/min) and were excluded, leaving 200 patients for analysis. Three definitions of drug-induced hyperkalemia were used: 1) a ≥ 1 mEq/L rise, 2) a >0.8 mEq rise in potassium in <24 hours warranting early discontinuation of TMP-SMX, and 3) "marked" hyperkalemia defined as serum potassium of ≥ 5.5 mEq/L within 48 hours. A potassium level before trimethoprim exposure (TxK) and after TxK were collected retrospectively. Demographic data were analyzed with Student's t-test and trimethoprim dose alone, demonstrating a significant difference. Analysis of 200 patients exposed to trimethoprim demonstrated an elevation of potassium (first definition) in 31 patients (15.5%), a rapid change in serum potassium in two patients (second definition), and marked hyperkalemia (>5.5 mEq/L) in 13 patients (6.5%). Hyperkalemia never occurred in 166 of 200 patients (82%; before TxK, 3.9 ± 0.4; after TxK, 4.3 ± 0.5 mEq/L). Change in serum potassium among patients with hyperkalemia was 4.0 ± 0.5 mEq/L before TxK and 5.3 ± 0.7 mEq/L after TxK. Twelve published hyperkalemia risk factors were reviewed in these 200 patients and only history of hypertension and need for intubation was more common in those with hyperkalemia. A nearly 20% incidence of hyperkalemia and 6% serious hyperkalemia in burn patients is consistent with reports in patients without burn injury. These data also suggest that the metabolic and hormonal changes associated with burn injury do not increase further the genetically predisposed hyperkalemia resulting from exposure to trimethoprim. These data suggest patients treated with TMP-SMX should have routine serum potassium monitoring before discharge.

The evaluation of the adrenal and thyroid axes and glucose metabolism after burn injury in children

INTRODUCTION

Burn injury is an important trauma and can cause many hormonal and metabolic changes in the human body. In contrast to the situation with adults, there are inadequate number of studies on children with this condition. Our aim in this study was to determine the changes in the adrenal, thyroid axes and glucose metabolism in the acute and subacute period and relation to the percent total body surface area (TBSA) burned in children with major burn injury.

PATIENTS AND METHOD

A total of 90 hospitalized children aged 0-13 years (mean: 3.44 +/- 2.90 years) with major fluid burn injury were included in this study. Serum ACTH, cortisol, fasting glucose and insulin and thyroid hormones (free T3 and T4, TSH) were evaluated in the first 24 hours after the burn injury and on day 3 and month 3 consequently in all of the cases. An ACTH stimulation test was performed when necessary. Continuous variables were compared with analysis of variance and categorical variables were compared with the chi-square test. The Pearson correlation was used to determine the relation between ACTH and cortisol and between blood glucose and insulin (on day 1 and 3 and month 3). Also the correlation with the TBSA burned and the hormonal values were evaluated. A p value <0.05 was considered statistically significant.

FINDINGS

ACTH and Cortisol level increased in first 24 hours and decreased significantly by time. The change of ACTH and Cortisol level with time was significantly related to the TBSA burned. ACTH and cortisol levels were found significantly correlated in each time-point, but the correlation was highest in 3rd month. The glucose level in the first 24 hours was significantly higher than day 3 and month 3 levels in all of the children. There was again a significant increase in the serum insulin level in the first 24 hours. However there was no difference between day 1 and 3 serum insulin levels. A correlation was found between serum glucose and insulin on the first day but not on day 3 or month 3. Free T3 and T4 levels increased by time. Pairwise comparisons indicated that 1st day free T3 and T4 level was significantly lower than both 3rd day and 3rd month levels.

CONCLUSION

ACTH, Cortisol and fasting blood glucose level increased significantly however serum insulin level was slightly higher in first 24 hours after burns in children. Thyroid hormones were found to be decreased acute period following burns but staying in normal levels.

Measurement of tissue cortisol levels in patients with severe burns: a preliminary investigation

Introduction

The assessment of adrenal function in critically ill patients is problematic, and there is evidence to suggest that measurement of tissue glucocorticoid activity may be more useful than estimation of plasma cortisol concentrations. Interstitial cortisol concentrations of cortisol represent the available pool of glucocorticoids able to enter the cell and bind to the glucocorticoid receptor. However the concentrations of plasma cortisol may not accurately reflect interstitial concentrations. We elected to perform a preliminary study into the feasibility of measuring interstitial cortisol by microdialysis, and to investigate the relationship between total plasma cortisol, free plasma cortisol and interstitial cortisol in patients with severe burns.

Methods

A prospective observational study carried out in a tertiary intensive care unit. Ten adult patients with a mean total burn surface area of 48% were studied. Interstitial cortisol was measured by microdialysis from patient-matched burnt and non-burnt tissue and compared with that of 3 healthy volunteers. Plasma sampling for estimations of total and free cortisol concentrations was performed concurrently.

Results

In the burn patients, mean total plasma and free plasma cortisol concentrations were 8.8 +/- 3.9, and 1.7 +/- 1.1 mcg/dL, (p < 0.001), respectively. Mean subcutaneous microdialysis cortisol concentrations in the burn and non-burn tissue were 0.80 +/- 0.31 vs 0.74 +/- 0.41 mcg/dL (p = 0.8), respectively, and were significantly elevated over the mean subcutaneous microdialysis cortisol concentrations in the healthy volunteers. There was no significant correlation between total plasma or free plasma and microdialysis cortisol concentrations. Plasma free cortisol was better correlated with total burn surface area than total cortisol.

Conclusions

In this preliminary study, interstitial cortisol concentrations measured by microdialysis in burnt and non-burnt skin from patients with severe thermal injury are significantly elevated over those from healthy volunteers. Plasma estimations of cortisol do not correlate with the microdialysis levels, raising the possibility that plasma cortisol may be an unreliable guide to tissue cortisol activity.

Bench-to-bedside review: Burn-induced cerebral inflammation--a neglected entity?

Severe burn injury remains a major burden on patients and healthcare systems. Following severe burns, the injured tissues mount a local inflammatory response aiming to restore homeostasis. With excessive burn load, the immune response becomes disproportionate and patients may develop an overshooting systemic inflammatory response, compromising multiple physiological barriers in the lung, kidney, liver, and brain. If the blood–brain barrier is breached, systemic inflammatory molecules and phagocytes readily enter the brain and activate sessile cells of the central nervous system. Copious amounts of reactive oxygen species, reactive nitrogen species, proteases, cytokines/chemokines, and complement proteins are being released by these inflammatory cells, resulting in additional neuronal damage and life-threatening cerebral edema. Despite the correlation between cerebral complications in severe burn victims with mortality, burn-induced neuroinflammation continues to fly under the radar as an underestimated entity in the critically ill burn patient. In this paper, we illustrate the molecular events leading to blood–brain barrier breakdown, with a focus on the subsequent neuroinflammatory changes leading to cerebral edema in patients with severe burns.

Corticotropin and cortisol response to maximal exercise testing in central diabetes insipidus

BACKGROUND

It is known that arginine vasopressin (AVP) has a stimulatory effect on corticotropin (adrenocorticotropic hormone; ACTH) and cortisol secretion especially during stress. The present study was designed to investigate the effect of stress on ACTH and cortisol levels in patients with central diabetes insipidus (DI) with endogenous AVP deficiency receiving AVP therapy, and to determine whether these children need steroid replacement during stress.

METHODS

Seven patients with a median age of 12 years (range 7-13 years) with idiopathic central DI on appropriate Desmopressin (DDAVP) therapy (group 1) and seven healthy controls with a median age of 15 years (range 13-20 years; group 2) were included in the study. Acute stress was produced in all children by treadmill exercise, assessed by maximal oxygen consumption and heart rate. ACTH and cortisol levels were determined before and after exercise.

RESULTS

In group 1, median ACTH level after exercise (28.3 pg/mL) was not different from the median value (24.0 pg/mL) before exercise. However, median cortisol level (10.5 microg/dL) was significantly increased (14.9 microg/dL; P < 0.05) with exercise. In group 2, cortisol (median 9.3 microg/dL) and ACTH levels (median 6.3 pg/mL) were significantly increased after exercise (15 mug/dL and 13.6 pg/mL, respectively; P < 0.05). There was no significant difference between the groups with respect to cortisol levels before and after exercise, but the stimulated ACTH levels after exercise were higher in patients with DI than in the controls (P < 0.05). A positive correlation was observed between total daily DDAVP dose and cortisol level after exercise (r(s)= 0.786, P < 0.05).

CONCLUSIONS

Cortisol response during acute stress is normal in children with DI and these patients do not need extra steroid treatment during stress. In contrast, the normal cortisol response obtained by increased ACTH levels in these patients indicates an increased sensitivity of corticotroph cells.

Elevated circulating leukemia inhibitory factor in patients with extensive burns

To investigate circulating cytokine responsiveness in major burns in association with the systemic stress response system, we tested hypothalamic-pituitary-adrenal (HPA) axis markers in extensive burn cases treated in the Department of Plastic and Reconstructive Surgery at Nagasaki University. The HPA axis is a major stress response system, and the leukemia inhibitory factor (LIF) may be a potent mediator of the HPA axis; therefore, circulating LIF levels in burn patients were studied. Twenty extensively burned patients (burn surface area, >20%), ie, 10 women and 10 men, 37 to 77 years of age (average: 59.1 +/- 12.10 years), were assessed. Circulating LIF, adrenocorticotropic hormone (ACTH), other inflammatory markers, and 24-hour urinary free cortisol excretion levels were investigated. LIF levels were greater in patients who died than in those who survived (186.1 +/- 80.41, 83.5 +/- 64.49 pg/ml, respectively, P < .001) at 36 hours after injury. ACTH levels were more significantly elevated in fatal cases than in those who survived. (41.3 +/- 8.28, 25.2 +/- 7.84 pg/ml, respectively, P < .0001). Twenty-four hour (24 to 48 hours after injury) pooled urinary free cortisol excretion levels also were significantly greater in fatal cases than in the surviving patient group (235.0 +/- 36.49 microg/day, 69.0 +/- 18.04 microg/day, respectively, P < .0001). The correlation between serum LIF and urine free cortisol was significant (r = .30; P < .01) as was the correlation of serum LIF with plasma ACTH (r = .24; P < .01). Serum LIF as well as HPA axis activity markers is a good marker of disease severity and prognosis in patients with extensive burns.

Possible role of CRF peptides in burn-induced hypermetabolism

Hypermetabolism and anorexia are significant problems associated with major burn trauma. Recent studies have shown that hypothalamic corticotropin releasing factor (CRF) elevates metabolic rate, while neuropeptide Y (NPY) reduces it. CRF also elicits anorexia, while NPY stimulates feeding. We hypothesized that elevation of CRF and decrease of NPY may be mediators of these negative effects of burn trauma. Therefore, we assessed concentrations of CRF and NPY in hypothalamus of burned rats one, three, and twenty-one days after a 30% body surface area, full-thickness, open flame burn. In addition we determined whether a biochemical lesion of CRF receptors using 3rd ventricle injections of a saporin-CRF conjugated peptide would decrease resting energy expenditure (REE). We found a three-day period of anorexia, with REE significantly increasing three days after the burn trauma. Concentrations of NPY were increased in the PVN-containing dorsomedial region of the hypothalamus 1 and 3 days after burn trauma, but were increased further in the day 1 pair-fed rats suggesting this change was a consequence of the anorexia. Levels of CRF were decreased in the ventromedial region of the hypothalamus in day 1 and day 3 burned and PF rats. Treatment with the saporin-CRF conjugate normalized REE and reduced CRF receptor-2 density in the hypothalamus of burned rats, and blocked CRF-induced hypermetabolism in sham-burned rats. Although these results suggest a role of CRF receptors in mediating burn-induced hypermetabolism, CRF itself may not be the principle ligand, as suggested by the significant elevation of hypothalamic urocortin 15 days after burn injury.

Prebiotic ingestion does not improve gastrointestinal barrier function in burn patients

Prebiotics increase intestinal levels of health-promoting bacteria implicated in decreasing pathogen colonization, stimulating immune functions and stabilizing gut barrier functions, parameters which are altered in burn patients. We propose that regular intake of a prebiotic, oligofructose (OF), might help to improve the altered gastrointestinal (GI) permeability observed in burn patients. A randomized, double-blind, controlled clinical trial was carried out in 41 burn patients (mean burn surface area=17.1+/-8.2%) who ingested daily 6 g of oligofructose (OF group) or sucrose as placebo (Control group) during 15 days. Gastrointestinal permeability to sucrose and lactulose/mannitol (L/M) was evaluated on days 1 (before treatment) 3, 7, 14 and 21. A permeability test was also performed in 18 healthy subjects as controls. Thirty-one patients completed the protocol (dropout rate=24.4%). Healthy subjects had a basal sucrose excretion of 21.3 mg (14.0-32.5 mg) and a basal L/M ratio of 0.017% (0.009-0.022%). Sucrose excretion increased 5-fold and L/M ratio 4.4-fold in burn patients on day 1 and these high levels of marker excretion decreased significantly throughout the study (p=0.016 and 0.000001, respectively). No differences between the OF and Control groups were observed for sucrose excretion or L/M ratio. In conclusion, the normalization of gastrointestinal permeability is not accelerated by prebiotic intake.

Reprogramming of the immune system during zinc deficiency

Thymic atrophy, lymphopenia, and compromised cell- and antibody-mediated responses that cause increased rates of infections of longer duration are the immunological hallmarks of zinc deficiency (ZD) in humans and higher animals. As the deficiency advances, a reprogramming of the immune system occurs, beginning with the activation of the stress axis and chronic production of glucocorticoids that accelerate apoptosis among pre-B and -T cells. This reduces lymphopoiesis and causes atrophy of the thymus. In contrast, myelopoiesis is preserved, thereby providing protection for the first line of immune defense or innate immunity. Changes in gene expression for cytokines, DNA repair enzymes, zinc transporters, signaling molecules, etc., suggest that cells of the immune system are attempting to adapt to the stress of suboptimal zinc. Better understanding of the molecular and cellular changes made in response to inadequate zinc should lead to the development of immunotherapeutic interventions.

Burn injury enhances brain prostaglandin E2 production through induction of cyclooxygenase-2 and microsomal prostaglandin E synthase in cerebral vascular endothelial cells in rats

OBJECTIVES

To examine whether peripheral burn injury in rats elevates prostaglandin E2 in the central nervous system and to determine where in the central nervous system enzymes responsible for prostaglandin E2 synthesis are expressed.

DESIGN

Prospective controlled animal study.

SETTING

University research laboratory.

SUBJECTS

Sprague-Dawley rats.

INTERVENTIONS

Rats received either approximately 25% full-thickness burn injury or sham treatment. At 36 hrs after the injury, the cerebrospinal fluid was sampled to measure prostaglandin E2, and the brain and the spinal cord were sampled for immunohistochemical detection of cyclooxygenase-2 and microsomal-type prostaglandin E2 synthase, enzymes that are responsible for prostaglandin E2 production.

MEASUREMENTS AND MAIN RESULTS

The prostaglandin E2 concentration in the cerebrospinal fluid was significantly elevated in the injured rats, and this elevation was suppressed by a cyclooxygenase-2-specific inhibitor, NS398. Only in the injured rats, cyclooxygenase-2 and microsomal-type prostaglandin E synthase proteins were detected in vascular endothelial cells throughout the central nervous system with no regional difference. A double-immunofluorescence study revealed that cyclooxygenase-2 and microsomal-type prostaglandin E synthase were coexpressed in the perinuclear region of the endothelial cells.

CONCLUSIONS

These results indicate that peripheral burn injury induces cyclooxygenase-2 and microsomal-type prostaglandin E synthase in endothelial cells of the central nervous system. These enzymes likely elevate the cerebrospinal fluid concentration of prostaglandin E2, a prostanoid that, in turn, activates prostaglandin E2 receptors on the central nervous system neurons involved in the general symptoms following burn injury.

Serum Levels of Prolactin, Growth Hormone, and Cortisol in Burn Patients: Correlations with Severity of Burn, Serum Cytokine Levels, and Fatality

In this study, we measured serum prolactin (PRL), cortisol, growth hormone, interleukin (IL)-1beta, IL-6, IL-8, IL-10, IL-12, and tumor necrosis factor-alpha in patients admitted with small-to-moderate burn injuries. Serum samples were obtained at the time of admission from 49 adult male burn patients with ages ranging from 18 to 91 years and TBSA ranging from 0.001 to 60%. The levels of serum PRL, IL-8, IL-6, and IL-1beta correlated positively with the TBSA, whereas only serum IL-8 levels correlated positively with fatality. Each of these factors were increased at least 2-fold at the higher burn severity. Not surprisingly, there was a large degree of variability in the hormone and cytokine levels in this patient population, which presumably reflects individual levels of stress, as well as other physiological variables. We also studied relationships between serum hormone levels and serum cytokine levels in this context. Linear regression analysis revealed a significant positive correlation between the serum PRL level and the levels of IL-10, IL-6, and IL-8. These results indicate that PRL responds to burn injury at early time points and that a subset of cytokines are involved in the early response to burn injury.

Impaired basal glucose effectiveness but unaltered fasting glucose release and gluconeogenesis during short-term hypercortisolemia in healthy subjects

Excess cortisol has been demonstrated to impair hepatic and extrahepatic insulin action. To determine whether glucose effectiveness and, in terms of endogenous glucose release (EGR), gluconeogenesis, also are altered by hypercortisolemia, eight healthy subjects were studied after overnight infusion with hydrocortisone or saline. Glucose effectiveness was assessed by a combined somatostatin and insulin infusion protocol to maintain insulin concentration at basal level in the presence of prandial glucose infusions. Despite elevated insulin concentrations (P < 0.05), hypercortisolemia resulted in higher glucose (P < 0.05) and free fatty acid concentrations (P < 0.05). Furthermore, basal insulin concentrations were higher during hydrocortisone than during saline infusion (P < 0.01), indicating the presence of steroid-induced insulin resistance. Postabsorptive glucose production (P = 0.64) and the fractional contribution of gluconeogenesis to EGR (P = 0.33) did not differ on the two study days. During the prandial glucose infusion, the integrated glycemic response above baseline was higher in the presence of hydrocortisone than during saline infusion (P < 0.05), implying a decrease in net glucose effectiveness (4.42 +/- 0.52 vs. 6.65 +/- 0.83 ml.kg-1.min-1; P < 0.05). To determine whether this defect is attributable to an impaired ability of glucose to suppress glucose production, to stimulate its own uptake, or both, glucose turnover and "hot" (labeled) indexes of glucose effectiveness (GE) were calculated. Hepatic GE was lower during cortisol than during saline infusion (2.39 +/- 0.24 vs. 3.82 +/- 0.51 ml.kg-1.min-1; P < 0.05), indicating a defect in the ability of glucose to restrain its own production. In addition, in the presence of excess cortisol, glucose disappearance was inappropriate for the prevailing glucose concentration, implying a decrease in glucose clearance (P < 0.05). The decrease in glucose clearance was confirmed by the higher increment in [3-3H]glucose during hydrocortisone than during saline infusion (P < 0.05), despite the administration of identical tracer infusion rates. In conclusion, short-term hypercortisolemia in healthy individuals with normal beta-cell function decreases insulin action but does not alter rates of EGR and gluconeogenesis. In addition, cortisol impairs the ability of glucose to suppress its own production, which due to accumulation of glucose in the glucose space results in impaired peripheral glucose clearance. These results suggest that cortisol excess impairs glucose tolerance by decreasing both insulin action and glucose effectiveness.

Surfactant phosphatidylcholine in thermally injured pigs

OBJECTIVE

To investigate the effect of a thermal injury on pulmonary surfactant phosphatidylcholine kinetics.

DESIGN

Random, controlled study.

SETTING

University research laboratory.

SUBJECTS

Yorkshire swine (n = 8) with and without a 40% total body surface area burn.

INTERVENTIONS

A new isotope tracer methodology was used to quantify surfactant phosphatidylcholine kinetics. Four days after burn, [1,2-13C2]acetate and [U-(13)C16]palmitate were infused continuously for 8 hrs to quantify surfactant phosphatidylcholine synthesis, secretion, recycling, and irreversible loss.

MEASUREMENTS AND MAIN RESULTS

The total surfactant phosphatidylcholine pool size was reduced from the control value of 2.65 +/- 0.05 to 1.61 +/- 0.08 micromol/g wet lung in burned animals (p <.05), as was the proportional contribution of palmitate to lung surfactant phosphatidylcholine composition. This reduction was associated with a significant decrease in lung dynamic compliance from the control value of 66 +/- 6 to 55 +/- 6 mL/cm H2O for burned pigs (p <.05). The most prominent response of lung phosphatidylcholine kinetics was a decrease in the total lung phosphatidylcholine synthesis from a control value of 12.7 +/- 1.2 to 5.5 +/- 0.3 nmol phosphatidylcholine-bound palmitate x hr(-1) x g of wet lung(-1) in burned animals (p<.05).

CONCLUSIONS

Pulmonary phosphatidylcholine content and palmitate composition decrease after burn injury because of a decrease in the rate of phosphatidylcholine synthesis. These responses likely contribute to impaired lung compliance.

Thermal injury effects on intestinal crypt cell proliferation and death are cell position dependent

We examined the effects of thermal injury on intestinal epithelial cell proliferation and death. We recorded histologically identifiable mitotic and apoptotic crypt cells in relation to cell position after a 60% full thickness cutaneous thermal injury in the rat. The injury significantly reduced mitosis (0.53 +/- 0.11 vs. 1. 50 +/- 0.70, P < 0.05) at cell positions 4-6, stem cells, 6 h after injury. A similar reduction in mitosis (1.13 +/- 0.59 vs. 3.50 +/- 0. 80, P < 0.05) was observed at higher cell positions 7-9 12 h after injury, indicating a positional cell shift. In addition, a significant increase in the number of apoptotic bodies occurred at cell positions 7-9 (2.32 +/- 0.87 vs. 0.13 +/- 0.22, P < 0.05) and 10-12 (2.2 +/- 0.12 vs. 0.00, P < 0.05) 6 h after injury. Thermal injury-induced alterations in mitotic and apoptotic activities were transient since crypts recovered with a moderate increase in mitotic activity 24 h after injury. In control and thermal-injury rats 24 h after injury, crypt cell mitosis and apoptosis did not differ significantly. This demonstrates that cutaneous thermal injury causes a transient suppression of mitosis as well as induction of apoptosis in a cell position-dependent manner in the small intestinal crypt.