Urinary Desmosine Levels Research Articles

Urine Desmosine as a Novel Biomarker for Bronchopulmonary Dysplasia and Postprematurity Respiratory Disease in Extremely Preterm or Low Birth Weight Infants.

This study aimed to evaluate whether elevated urine desmosine levels at 3 weeks of age were associated with severe radiological findings, bronchopulmonary dysplasia (BPD), and post-prematurity respiratory disease (PRD) in extremely preterm (EP) or extremely low birth weight (ELBW) infants. This study recruited 37 EP (22-27 completed weeks) or ELBW (<1,000 g) infants. Urine was collected between 21 and 28 postnatal days, and desmosine was measured using an enzyme-linked immunosorbent assay kit; the urine creatinine level was also measured. Bubbly/cystic lungs were characterized by emphysematous chest X-rays on postnatal day 28. Furthermore, provision of supplemental oxygen or positive-pressure respiratory support at 40 weeks' postmenstrual age defined BPD, and increased medical utilization at 18 months of corrected age defined PRD. The desmosine/creatinine threshold was determined by receiver operating characteristic analysis. The adjusted risk and 95% confidence interval (CI) for elevated urine desmosine/creatinine levels were estimated by logistic regression analysis. Elevated urine desmosine/creatinine levels higher than the threshold were significantly associated with bubbly/cystic lungs (8/13 [61.5%] vs. 2/24 [8.3%], p = 0.001), BPD (10/13 [76.9%] vs. 8/24 [33.3%], p = 0.02), and PRD (6/13 [46.2%] vs. 2/24 [8.3%], p = 0.01). After adjusting for gestational age, birth weight, and sex, the urine desmosine/creatinine levels were significantly higher in those who were highly at risk of bubbly/cystic lungs (odds ratio [OR], 13.2; 95% CI, 1.67-105) and PRD (OR, 13.8; 95% CI, 1.31-144). Elevated urine desmosine/creatinine levels on the third postnatal week were associated with bubbly/cystic lungs on day 28 and PRD at 18 months of corrected age in EP or ELBW infants. · Urine desmosine was prospectively measured in 3-week-old EP/ELBW infants.. · Elevated urine desmosine levels were associated with emphysematous radiological findings on day 28, PRD at 18 months of corrected age.. · Urine desmosine may be a promising biomarker indicating lung damage in EP/ELBW infants..

Kronik Obstrüktif Akciğer Hastalığında Fenotiplere Göre Kanda ve İdrarda Biyobelirteçlerin Karşılaştırılması: Kesitsel Araştırma

Objective: Chronic obstructive pulmonary disease (COPD) is one of the leading causes of morbidity and mortality worldwide. Biomarkers have been recognized as an important tool in assessing COPD patients. In this study, we aimed to investigate the possible relationship between certain biomarkers and different COPD phenotypes. Material and Methods: Between January 1, 2017-December 31, 2017, a total of 85 patients who were admitted to the Çanakkale Onsekiz Mart University Faculty of Medicine Hospital Chest Diseases Outpatient Clinic with a diagnosis of COPD according to the Global Initiative for Chronic Obstructive Lung Disease 2017 Guidelines were included in this study. All patients filled in the COPD Assessment Test and modified Medical Research Council questionnaires. Patients were divided into 4 phenotypes: emphysema, chronic bronchitis, frequent exacerbation, and asthma COPD overlap syndrome (ACOS). Levels of C-reactive protein (CRP), desmosine, fibronectin, eotaxin, and interleukin (IL)-2 were measured and compared between the phenotypes. Results: The mean age was 64.56 years and 92.9% of the study population were males. Of 85 patients, 43 had emphysema, 13 had frequent exacerbation, 15 had chronic bronchitis, and 14 had ACOS phenotype. Blood fibronectin, eotaxin, and urine desmosine levels were significantly lower in patients with ACOS phenotype compared to the other phenotypes. In patients with the frequent exacerbation phenotype, the CRP level was significantly higher than that of the other three phenotypes. The IL-2 levels were similar in all phenotypes. Conclusion: Our study results suggest that these biomarkers may be useful in the differential diagnosis of COPD phenotypes.

Lung injury in patients age 75 years and older with the use of polymethylmethacrylate fenestrated pedicle screws

Pulmonary complications in patients age 75 years and older who undergo spinal fusion may have catastrophic consequences. The use of augmentation techniques with polymethylmethacrylate (PMMA) have been associated with pulmonary damage. The use of fenestrated pedicle screws augmented with PMMA may increase the risk of lung injury in this population. To investigate whether the use of PMMA-augmented screws is correlated with increased lung injury in patients undergoing instrumented lumbar spinal fusion. A nonrandomized, prospective, case-controlled clinical study was carried out. We included 50 consecutive patients: 25 classifieds as patients who required PMMA-augmented screws in lumbar spinal fusion, and 25 classifieds as control participants because they underwent uncemented instrumented spinal fusion. We compare the incidence of the event, lung damage, in both groups by measuring a series of parameters: arterial blood gas, transesophageal echocardiography, urinary desmosine, and chest radiograph. The epidemiological parameters analyzed were age, sex, body mass index, status as a smoker, and number of cement leaks. Changes in pulmonary damage markers were described in both groups of patients, comparing postsurgery values with baseline values. In control participants, each change was evaluated for the total number of patients. All changes are indicated in this report by mean differences for quantitative variables and by differing proportions for qualitative variables, with 95% confidence intervals provided for all values. There was an increase in postinstrumentation PaO2 (arterial partial pressure of oxygen) in both groups, probably related to the use of mechanical ventilation and recruitment maneuvers. Even though the group that required augmentation had lower baseline levels, the difference between groups was not statistically significant. On transesophageal echocardiographs, we observed scattered small, snowflake-like emboli, and bright echo signals appeared in the right atrium during PMMA injection. Signal density was constant but gradually faded away when PMMA injection ended. No participants in the group without augmentation had radiological complications. Overall, desmosine levels increased in both groups, and the rise was similar in both. There was a slight average increase in urine desmosine levels after instrumentation and progressively continues to rise until 24 hours after instrumentation, with a subsequent decrease at 72 hours. Comparing the two groups, we found no statistically significant differences at any time. We were not able to identify a significant difference in urine desmosine levels associated with the augmentation of with fenestrated pedicle screws with PMMA. Despite comparing patients age 75 years or older with a younger group, we found no clinical, analytical, or gasometric data indicating lung damage in patients who had augmentation.

P6505Urinary desmosine, an elastin-specific degradation product is associated with maximum aortic root size and aortic z-scores in patients with bicuspid aortic valve

Abstract Background Bicuspid aortic valve (BAV) is the commonest congenital cardiac abnormality affecting up to 2% of the general population. BAV is highly diverse in phenotype however a common feature is its inherent risk of morbidity and mortality from aortic root dilatation and dissection. Aortic dilatation involves elastin degradation and desmosine is an amino acid cross-link that is released into the bloodstream and urine following elastin degradation. It is known from an earlier pilot study (DESMA) of desmosine in Marfan Syndrome (MFS) patients that plasma desmosine among patients with MFS is significantly elevated and correlates with aortic size however whether this same observation is seen in other forms of inherited aortopathies such as BAV is unclear. Objectives 1. To investigate whether patients with BAV have higher elastin degradation as indicated by plasma desmosine and urinary desmosine levels. 2. To explore the relationship between plasma and urinary desmosine levels with aortic root size in patients with BAV. Methods We measured urinary (ng/mg creatinine) and plasma desmosine (ng/mL) in 20 patients with BAV and healthy control subjects using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Aortic root size and corresponding Z-scores were measured on echocardiogram. Correlation was analysed with Spearman's rank test. Results The patients with BAV were predominantly male (n=15, 75%) with a mean age of 50.5 years ± 17.6 [SD]. All the BAV patients had normal LV systolic function and none had prior aortic root surgery or were current smokers. Nine BAV patients had treated hypertension. Compared to controls, both plasma desmosine (0.30±0.10 vs 0.26±0.075 ng/mL, p=0.01) and urinary desmosine (15.9±4.6 vs 7.2±2.8 ng/mg creatinine, p&lt;0.001) were significantly elevated in patients with BAV. Urinary and plasma desmosine (Figure 1) were also significantly correlated (r=0.55, p=0.01). There was a significant association between urinary desmosine and maximal aortic root size and Z-scores in the BAV cohort (Figure 2) compared to controls (p=0.02), however this was not seen with plasma desmosine. Conclusions Urinary and plasma desmosine levels are significantly higher in patients with BAV compared to controls. Urinary desmosine is also significantly associated with maximal aortic root size, reflecting higher elastin degradation. This suggests a potential use of desmosine as a biomarker to monitor disease progression in patients with BAV. Acknowledgement/Funding Anonymous Trust

Elastin turnover in malignant solid tumors

Desmosine, a crosslinking amino acid unique to elastin, was investigated as a possible biomarker for cancer. Twenty-eight normal controls, median age 67 years, had a median value for urine desmosine of 43.5 picomoles desmosine/mg creatinine. The median for 19 untreated cancer subjects of similar age was significantly higher (175 picomoles desmosine/mg creatinine, p < 0.001). Urine desmosine levels in 55 subjects currently receiving chemotherapy, as well as 67 individuals who had survived cancer and were currently clinically disease free, were not significantly different from controls. Our findings indicate that elastin is being turned over in malignant solid tumors, releasing significantly elevated levels of desmosine in the urine.

Steroid Modulation of Cytokine Release and Desmosine Levels in Bilateral Total Knee Replacement

The perioperative inflammatory response as measured by elevated levels of interleukin-6 (IL-6) has been linked to acute respiratory distress syndrome, postoperative confusion, and fever. Because of the extent of surgery,patients undergoing bilateral total knee arthroplasty may be at high risk of complications. We had found a significant decrease in IL-6 in patients having bilateral total knee replacement who received two doses of 100 mg of hydrocortisone eight hours apart; however, by twenty-four hours, IL-6 levels were equal to those in the group that received a placebo. In the present study, we investigated whether the administration of three doses would reduce IL-6 levels at twenty-four hours and affect other outcomes such as desmosine level, a marker of lung injury. After institutional review board approval, a total of thirty-four patients (seventeen patients and seventeen control subjects) were enrolled in this double-blind, randomized, placebo-controlled study. Three doses of intravenous hydrocortisone (100 mg) or placebo were given eight hours apart. Urinary desmosine levels were obtained at baseline and at one and three days postoperatively. The level of IL-6 was measured at baseline and at six, ten, twenty-four, and forty-eight hours postoperatively. Pain scores, presence of fever, and functional outcomes were recorded. The level of IL-6 increased in both groups, but was significantly higher in the control group, peaking at twenty-four hours (mean and standard deviation, 623.74 ± 610.35 pg/mL versus 148.13 ± 119.35 pg/mL; p = 0.006). Urinary desmosine levels significantly increased by twenty-four hours in the control group, but remained unchanged in the study group (134.75 ± 67.88 pmol/mg and 79.45 ± 46.30 pmol/mg, respectively; p = 0.006). Pain scores at twenty-four hours were significantly lower in the study group (1.4 ± 0.9 versus 2.4 ± 1.2; p = 0.01) as was the presence of fever (11.8%versus 47.1%; p = 0.03). Range of motion at the knee was significantly greater in the study group (81.6 ± 11.6 versus 70.6 ± 14.0 in the right knee [p = 0.02] and 81.4 ± 11.3 versus 73.4 ± 9.4 in the left knee [p = 0.03]). Hydrocortisone (100 mg) given over three doses, each eight hours apart, decreased and maintained a lower degree of inflammation with bilateral total knee replacement as measured by IL-6 level. Corticosteroids decreased the prevalence of fever, lowered visual analog pain scores, and improved knee motion. The significantly lower values of desmosine in the study group suggest that this treatment may be protective against lung injury.

Clinical validity of plasma and urinary desmosine as biomarkers for chronic obstructive pulmonary disease

BackgroundAlthough an increased concentration of degraded elastin products in patients with chronic obstructive pulmonary disease (COPD) has been reported for many years, its clinical validity and utility remain uncertain due...

The effect of low versus high tidal volume ventilation on inflammatory markers in healthy individuals undergoing posterior spine fusion in the prone position: a randomized controlled trial

Study ObjectiveTo evaluate the effect of ventilation strategy on markers of inflammation in patients undergoing spine surgery in the prone position. DesignRandomized controlled trial. SettingUniversity-affiliated teaching hospital. Patients26 ASA physical status 1 and 2 patients scheduled for elective primary lumbar decompression and fusion in the prone position. InterventionsPatients were randomized to receive mechanical ventilation with either a tidal volume (VT) of 12 mL/kg ideal body weight with zero positive end-expiratory pressure (PEEP) or VT of 6 mL/kg ideal body weight with PEEP of 8 cm H2O. MeasurementsPlasma levels of interleukin (IL)-6 and IL-8 were determined at the beginning of ventilation and at 6 and 12 hours later. Urinary levels of desmosine were determined at the beginning of ventilation and on postoperative days 1 and 3. Main ResultsA significant increase in IL-6, IL-8, and urine desmosine levels was noted over time compared with baseline (P < 0.01). However, no significant difference in the levels of markers was seen between the groups at any time point when controlling for demographics, ASA physical status, body mass index, duration of ventilation, or estimated blood loss. ConclusionsAlthough markers of inflammation are increased after posterior spine fusion surgery, ventilation strategy has minimal impact on markers of systemic inflammation.

The Utility of Urine Desmosine as a Marker of Lung Injury in Spine Surgery

The objective of this prospective observational study was to determine if urine desmosine levels, a marker of lung injury, increase in response to the periopreative insults of anterior and posterior spine surgery. Desmosine, a stable breakdown product of elastin, has been proposed as a surrogate marker of lung injury in patients with COPD, tobacco use, and ARDS. We recently evaluated this marker in patients undergoing knee surgery, but the utility of desmosine as a marker of lung injury in patients undergoing spine surgery remains unstudied. In this study, we enrolled ten consecutive patients, who underwent anterior/posterior spine surgery. Patient demographics and perioperative data were recorded. Urine samples were collected at baseline, 1day, and 3days postoperatively and analyzed for levels of desmosine using a previously validated radioimmunoassay. Desmosine levels were 35.9 ± 18.2pmol/mg creatinine at baseline, 38.7 ± 11pmol/mg creatinine on postoperative day 1, and 70.5 ± 49.1pmol/mg creatinine on postoperative day 3, respectively. Desmosine/creatinine ratios measured on day 3 postoperatively were significantly elevated compared to levels at baseline, and represented a 96.3% increase. No difference was seen between levels at baseline and day 1 postoperatively. In conclusion, we were able to show a significant increase in urine desmosine levels associated with anterior/posterior spine surgery. In the context of previous studies, our findings suggest that desmosine may be a marker of lung injury in this setting. However, further research is warranted for validation and correlation of desmosine levels to clinical markers and various degrees of lung injury.

Urine desmosine as a marker of lung injury following total knee arthroplasty. A pilot study.

Lung injury following total knee arthroplasty (TKA) may occur secondary to embolization of bone debris, fat, and cement. Clinically relevant respiratory failure is rare and is therefore difficult to study. To facilitate future investigations on this subject, we evaluated the utility of the elastin breakdown product desmosine as a potential marker of lung injury during TKA surgery. The goals of this study were to answer (1) if desmosine levels would increase in response to the perioperative insults in patients undergoing TKA and (2) if this increase would differ among unilateral and bilateral TKA procedures. Twenty consecutive patients (ten unilateral and ten bilateral TKAs) were enrolled. Urine samples were collected before surgery and at 1 and 3 days postoperatively and analyzed for levels of desmosine using a validated radioimmunoassay. Baseline desmosine/creatinine ratios were higher in the unilateral as compared to the bilateral TKA group (p = 0.003). Tourniquet times, intraoperative estimated blood loss, and transfusion requirements among bilateral TKA patients were significantly higher than those of unilateral TKA recipients. Desmosine levels increased in both groups, but the rise was significant only in the bilateral group. We detected a significant increase in urine desmosine levels associated with bilateral but not unilateral TKA surgery. In the context of previous studies, our findings suggest that desmosine may be a marker of postoperative lung injury. Further research is warranted for validation and correlation of desmosine levels to clinical markers and various degrees of lung injury.

Higher urine desmosine levels are associated with mortality in patients with acute lung injury.

Desmosine is a stable breakdown product of elastin that can be reliably measured in urine samples. We tested the hypothesis that higher baseline urine desmosine would be associated with higher mortality in 579 of 861 patients included in the recent Acute Respiratory Distress Syndrome Network trial of lower tidal volume ventilation (1). We also correlated urine desmosine levels with indexes of disease severity. Finally, we assessed whether urine desmosine was lower in patients who received lower tidal volumes. Desmosine was measured by radioimmunoassay in urine samples from days 0, 1, and 3 of the study. The data were expressed as a ratio of urine desmosine to urine creatinine to control for renal dilution. The results show that higher baseline (day 0) urine desmosine-to-creatinine concentration was associated with a higher risk of death on adjusted analysis (odds ratio 1.36, 95% confidence interval 1.02-1.82, P=0.03). Urine desmosine increased in both ventilator groups from day 0 to day 3, but the average rise was higher in the 12-ml/kg predicted body weight group compared with the 6-ml/kg predicted body weight group (P=0.053, repeated-measures model). In conclusion, patients with acute lung injury ventilated with lower tidal volumes have lower urine desmosine levels, a finding that may reflect reduced extracellular matrix breakdown. These results illustrate the value of evaluating urinary biological markers that may have prognostic and pathogenetic significance in acute lung injury.

Urinary desmosine as a biomarker in acute lung injury

Acute lung injury (ALI) is a complex disorder associated with an acute inflammatory response thought to contribute to tissue injury. Desmosine, a cross-linking amino acid present in elastin, is released during matrix degradation and cleared by the kidney. Results from animal models and human disease studies have suggested that ALI is associated with the release of desmosine, resulting in increased urinary desmosine. A radioimmunoassay was used to monitor urinary desmosine levels over 10 days in ten patients with ALI. The concentration of desmosine was measured with and without acid hydrolysis. Baseline urinary desmosine was increased in two of ten patients. The concentration of desmosine at baseline did not appear to be related to age, gender, neutrophil elastase (NE)/α1-antiprotease complex concentration or PaO2/FiO2 ratio. No meaningful changes in desmosine levels were noted after removal from mechanical ventilation. Baseline desmosine concentrations did not appear to correlate with the risk of death. The limited sensitivity, predictive correlations and dynamic modulation would suggest that urine desmosine has a limited role as a biomarker for ALI. Hydrolysis of urine samples appears necessary for optimal measurement of urine desmosine.

Short-term variability of biomarkers of proteinase activity in patients with emphysema associated with type Z alpha-1-antitrypsin deficiency

BackgroundThe burden of proteinases from inflammatory cells in the lung of subjects with type Pi ZZ of alpha-1-antitrypsin deficiency is higher than in those without the deficiency. Cross-sectional studies have shown increased levels of biomarkers of extracellular matrix degradation in vivo. Longitudinal variability of these biomarkers is unknown but desirable for clinical studies with proteinase inhibitors.MethodsWe measured three different types of biomarkers, including desmosines, elastase-formed fibrinogen fragments and heparan sulfate epitope JM403, in plasma and urine for a period of 7 weeks in a group of 12 patients who participated in a placebo-controlled study to assess the safety of a single inhalation of hyaluronic acid.ResultsEffect of study medication on any of the biomarkers was not seen. Baseline desmosines in plasma and urine correlated with baseline CO diffusion capacity (R = 0.81, p = 0.01 and R = 0.65, p = 0.05). Mean coefficient of variation within patients (CVi) for plasma and urine desmosines was 18.7 to 13.5%, respectively. Change in urinary desmosine levels correlated significantly with change in plasma desmosine levels (R = 0.84, p < 0.01). Mean CVi for fibrinogen fragments in plasma was 20.5% and for JM403 in urine was 27.8%. No correlations were found between fibrinogen fragments or JM403 epitope and desmosines.ConclusionWe found acceptable variability in our study parameters, indicating the feasibility of their use in an evaluation of biochemical efficacy of alpha-1-antitrypsin augmentation therapy in Pi Z subjects.

MEKC of desmosine and isodesmosine in urine of chronic destructive lung disease patients.

Degradation of extracellular matrix components is central to many pathological features of chronic destructive lung disorders. Desmosine and isodesmosine are elastin-derived cross-linked amino acids whose urine levels are considered representative of elastin breakdown. The aim of this study was to apply a novel methodology, based on high-performance capillary electrophoresis, to the quantification of desmosine and isodesmosine in 11 patients with stable chronic obstructive pulmonary disease (COPD), 10 with an exacerbation of COPD, nine with alpha1-antitrypsin deficiency, 13 with bronchiectasis, and 11 adults with cystic fibrosis, in comparison to 24 controls. It was found that, in patients with stable COPD, urinary desmosine levels were higher than in controls (p=0.03), but lower than in COPD subjects with an exacerbation (p< or =0.05). The highest desmosine levels were found in subjects with alpha1-antitrypsin deficiency, bronchiectasis and cystic fibrosis (p<0.001 versus stable COPD). In a short-term longitudinal study, five stable COPD patients showed a constant rate of desmosine excretion (mean coefficient of variation <8% over three consecutive days). In conclusion, the present method is simple and suitable for the determination of elastin-derived cross-linked amino acid excretion in urine, giving results similar to those obtained using other separation methods. In addition, evidence is presented that urinary desmosine excretion is increased in conditions characterized by airway inflammation, such as exacerbations of chronic obstructive pulmonary disease, bronchiectasis and cystic fibrosis. Results obtained in subjects with alphal-antitrypsin deficiency suggest that this method might be used to evaluate the putative efficacy of replacement therapy.

Measurement of Urinary Desmosine as an Indicator of Acute Pulmonary Disease

A modified radioimmunoassay (RIA) for desmosine in the urine was investigated as a tool for the rapid estimation of lung elastin catabolism. Cystic fibrosis (CF) and oxygen toxicity were chosen as conditions that might show altered elastin destruction. Using an antibody bound to magnetic particles the RIA was adapted to handle large numbers of samples requiring only 50 microliters or urine. The experiments show that it was not necessary to hydrolyze or extract the urine prior to assay and that collecting spot urines and normalizing the data to urine creatinine gives the same interpretation of the data as total desmosine in a 24-hour collection. Urine desmosine levels were elevated in 10 of 16 patients with CF; however, daily fluctuations were considerable in some subjects, varying as much as 5-fold and underlining the importance of assaying several consecutive days of urine in acute disorders for an accurate estimate of desmosine excretion. The RIA for desmosine is a rapid and sensitive assay that requires no sample preparation and could be applied to clinical situations that require large numbers of samples.

Urinary desmosine, elastolysis, and lung disease

Desmosine is an amino acid specific to elastin. Animal studies suggest that urinary desmosine (UD) represents endogenus elastin degradation. Therefore, UD has previously been used to investigate endogenous elastolysis, but was not elevated in subjects with chronic obstructive airways disease (COAD), although accelerated pulmonary elastolysis is thought to contribute to COAD. We have investigated whether this reflects large day-to-day and between-subject variation in UD and whether, in man, dietary desmosine contributes significantly to that in urine. Mean 24-hour UD output (over 5 consecutive days) from 10 asymptomatic subjects (5 males) was higher in males than females ( 77.4 ± 9.6 and 40.2 ± 5.0 nmol 24 hours , respectively; mean ± SD, P < .001), but not significantly different when expressed in terms of creatinine (μg desmosine/100 mg creatinine: males, 2.5 ± 0.4; females, 3.1 ± 0.8; mean ± SD). The lowest between-subject variation was observed when the mean of 5 days' 24-hour UD values was analyzed on the basis of gender (coefficient of variation [CV], 12.5%); when gender was not considered, the least between-subject variation was found for the mean of 5 days' desmosine/creatinine analysis (CV, 24.5%). Approximately 1% of dietary desmosine (ingested as [ 3H]elastin and [ 3H] desmosine) was excreted in the urine within 24 hours, contributing approximately 15% of UD while on a normal diet. Although ingestion of a low elastin diet ( < 1 10 desmosine/24 hours than a normal diet) resulted in lower within-subject variation in 24-hour UD excretion (mean CV decreased from 31.5% to 20.2%), the between-subject CV and UD levels did not alter. In a pilot study of subjects with bacterial pneumonia developing (1) in a normal lung (n = 3; 7 days' urine), and (2) in chronic lung disease (n = 3; 7 days' urine), elevated 24-hour UD was observed in two subjects (μg desmosine/100 mg creatinine, 7.3 ± 0.75 and 6.5 ± 1.9; mean ± SD). In subjects with α 1-proteinase inhibitor ( α 1PI) deficiency (n = 1, 18 days' urine; n = 11, 1 days' urine), only one 24-hour urine sample contained elevated μg desmosine/100 mg creatinine (5.44). Further studies are required on the use of UD as an index of in vivo elastolysis for clinical purposes.

Elastin turnover in the rat uterus.

During pregnancy the rat uterus shows a steady increase in total elastin content, reaching levels of 300% above non-pregnant controls. Elevated levels of urinary desmosine are also seen during this period. After parturition there is a slight lag period and then rapid removal of elastin from the uterus, reaching baseline after five days. Urinary desmosine levels were elevated for about seven days post partum before returning toward control levels. Analysis of pre- and post-partum serum showed no significant differences. The involuting rat uterus appears to be an excellent model for the study of processes involved in elastin catabolism.