Evaluation of the Urinary Desmosine Radioimmunoassay as a Monitor of Lung Injury after Endobronchial Elastase Instillation in Sheep

Thirty male sheep were treated with varying doses of endobronchial elastase. Urinary excretion of elastin peptides was then measured by desmosine radioimmunoassay and compared with pre-enzyme values. Mean linear intercepts were measured in treated and untreated lobes 4 wk later, and in addition, lung perfusion, ventilation, and volume were measured before enzyme treatment and 4 wk later using radionuclide-imaging techniques. Most of the elevation in urinary desmosine excretion occurred in the first 48 h after elastase administration. The increase in desmosine excretion was positively correlated with: enzyme dose (r = 0.74, p less than 0.01), increase in mean linear intercept (r = 0.61, p less than 0.05), decrease in lung perfusion (r = 0.77, p less than 0.01), and decrease in ventilation (r = 0.58, p less than 0.05). These results demonstrate that the urinary desmosine radioimmunoassay is a reliable index of pulmonary elastin breakdown and of several resultant anatomic and physiologic stigmata of pulmonary emphysema.

Peplomycin sulfate and pulmonary fibrosis: hydroxyproline, uronic acid, proline hydroxylase and glucosamine 6-phosphate synthetase in lungs of hamsters treated with peplomycin

Effect of peplomycin sulfate (PLM) on pulmonary fibrosis was examined. Hydroxyproline, uronic acid, proline hydroxylase (EC 1.14.11.2) and glucosamine 6-phosphate synthetase (EC 2.6.1.16) in lungs of hamsters treated with PLM were studied and compared with those of hamsters treated with bleomycin (BLM). PLM, when administered intraperitoneally, one injection daily for 10 consecutive days, at either a high- (5 mg/kg) or low- (2.8 mg/kg) dosage-level, caused no significant increase of lung hydroxyproline and uronic acid as compared with controls. BLM on the other hand effected a significant increase in lung hydroxyproline on the high-dosage level (5 mg/kg) but not on the low-dosage level (2.8 mg/kg). In contrast, when administering PLM intratracheally, the concentrations of hydroxyproline in lungs increased 20% over the control levels. A transient increase of proline hydroxylase and glucosamine 6-phosphate synthetase also occurred shortly after the instillation. These increases were also observed in the corresponding groups treated with BLM, which confirmed the previous observations by other investigators. However, the magnitude of the increase was relatively lower in those values of PLM as compared with those of BLM. These data suggested that (1) PLM, when administered with multiple dosages intraperitoneally, showed no significant effect on the elevation of lung hydroxyproline; (2) PLM, when administered with a dose intratracheally, induced pulmonary fibrosis similar to that caused by BLM. However, the hydroxyproline accumulation in lungs of PLM-treated hamsters was less than in those of the BLM-treated; (3) The fibrotic effect on the lungs caused by either PLM or BLM was probably attributed to acceleration of the syntheses of collagen and acidic glycosaminoglycans.

Different effects of selenium on cyclic AMP metabolism in hepatoma cells and normal liver cells

Sodium selenite administered to normal and hepatoma (HA)-bearing mice sc (2 mg/kg) or ip (1 mg/kg) led to a significant increase in cyclic AMP (cAMP) level and a decrease in cAMP phosphodiesterase (PDE) activity in HA cells. In contrast, in tumor host liver and normal liver the cAMP level was reduced, and the PDE activity was slightly elevated, whereas the cAMP adenylate cyclase (AC) was little affected by Na2SeO3, if at all. These results imply that selenite-induced changes in PDE activity play a decisive role in regulating intracellular cAMP level. Kinetic studies revealed that there were different forms of PDE. TheK m value of PDE isozymes in normal liver and host liver were identical, but differed from those of HA. It seems likely that the selective responsiveness of PDE to selenite may be related to the difference in PDE isozyme patterns. Addition of DBcAMP to the culture medium resulted in an inhibition of(3)H-thymidine incorporation into hepatoma cells, indicating that the inhibition of HA cell proliferation was cAMP-mediated. Thus, selenium has been shown to exert a selective effect on cAMP metabolism of hepatoma cells, which may account for its inhibitory effects on cancer cells.

Factors regulating lamellar body volume density of type II pneumocytes in excised dog lungs

Pulmonary arterial occlusion (PAO) produces multiple alterations in the physiological/biochemical environment of lung cells as well as dysfunction of the lung's surfactant system, which is considered to play a significant role in mediating lung injury. The present studies were performed using 66 excised dog lungs to evaluate the impact of alterations in ventilation, substrate availability, alveolar CO2 tension, hydrogen ion and bicarbonate concentrations, and temperature and neural denervation on the lamellar body (LB) volume density of type II pneumocytes. Ventilating excised nonperfused dog lungs with room air (0% CO2) for 4 h at 38 degrees C resulted in severe reductions (68-77%) in LB volume density. Supplementing inspired gas with 5% CO2 prevented LB depletion, while ventilation with 2.5% CO2 moderated the severity of depletion to 17-27% of control. Ventilation with 10% CO2 tended to increase LB volume density by increasing the number of LBs per cell, whereas reductions in LB volume density predominantly resulted from a decrease in LB size. The level of ventilation had no significant effect on LB volume density independent of inspired CO2 concentration. Reducing temperature to 5 degrees C prevented LB depletion. Lung perfusion with autologous whole blood failed to moderate the severity of LB depletion during room air ventilation despite the increased availability of metabolic substrates for cellular metabolism. Adding hydrochloric acid to maintain physiologically normal hydrogen ion concentrations in the perfusing blood had a small effect in ameliorating the severity of LB depletion. These results indicate that alveolar CO2 tension and bicarbonate concentration are major factors regulating the LB content of type II pneumocytes and suggest an important link between the gas exchange and phospholipid metabolic functions of the lung.

Urinary excretion of desmosine in patients with severe burns

Urinary excretion of total desmosine was measured by a radioimmunoassay in severely burned adult males, as well as in normal adult males. Total urinary desmosine was significantly elevated in all the samples in the burned patients, who had injuries involving more than 19% of total body surface area. The values of 24-hr urinary desmosine for the burned patients ranged from 250--1,411 nmoles, as compared with 82--142 nmoles for normal controls. These were equivalent to 14--78 mg of elastin degraded for the burned patients and 5--8 mg for normal controls. Urinary desmosine values expressed as nmoles per g of creatinine were also higher than the corresponding normal values, ranging from 110--768 nmoles versus 63 +/- 6 nmoles for normal controls. Urinary excretion of total hydroxyproline in the burned patients was also higher than in normal controls, ranging from 56--471 mg per 24 hrs, or 36 to 413 mg per g of creatinine, vs. 31 +/- 6 mg per 24 hr, or 23 +/- 2 mg per g of creatinine, in burned patients and normal controls, respectively. These values of hydroxyproline were equivalent to 413--3,623 mg of collagen and 238 mg of collagen, respectively. In the burned patients, both urinary desmosine and hydroxyproline values were elevated from day 1 post-burn, and reached peak levels in days 2--12, declining thereafter but remaining higher than values for normal controls through day 60. The metabolism of elastin and collagen in skin of burned patients was probably highly accelerated for a long time, at least through day 60 post-burn.

Desmosine radioimmunoassay for measuring elastin degradation in vivo

Desmosine is a cross-link amino acid unique to elastin. Previous work has shown that during turnover in the body, desmosine is not reused, and that desmosine is not absorbed from the intestine. Instead, all desmosine released in the course of elastin metabolism is excreted in the urine attached to low molecular weight peptides. Therefore, measurement of desmosine in acid-hydrolysates of urine might be used to monitor elastin breakdown in several pathologic states, including pulmonary emphysema. In the present report, we have described a sensitive, highly specific radioimmunoassay capable of detecting as little as 200 pg of desmosine in acid-hydrolysates of urine. The assay was specific for desmosine; cross-reactivity with merodesmosine, isodesmosine, lysine, and mixed amino acids was 0.25%, 0.1%, less than 0.0003%, and 0%, respectively. Twenty-three normal, nonsmoking subjects had a mean 24-hr desmosine excretion of 47 +/- 15 microgram. In a group of smokers with evidence of chronic obstructive disease and/or lung infection, the values for desmosine excretion ranged from 40 to 400 microgram/24 h. Desmosine radioimmunoassay may find application in the study of diseases involving increased destruction of elastin in the body.

Association of prealbumin deficiency with alpha-1-antitrypsin deficiency

Prealbumin (PA) measurements were made by electrophoretic and radial immunodiffusion techniques in three alpha-1-antitrypsin deficient Pi-D) serum samples. The deficiency was characterized as phenotype ZZ (homozygous). In two out of three serums PA was undetectable, as revealed by the absence of radiothyroxine distribution in the PA area, whereas quantitative estimates of PA by radial immunodiffusion showed very low levels (2--7 mg/100 ml) thus corroborating electrophoretic observations; low PA binding of T4 tracer was noted in another Pi-D serum. The total protein and laboratory thyroid function (thyroxine, triiodothyronine, and free thyroxine index concentration) measurements were normal, and the decrease in PA could not be explained on the basis of surgery, protein malnutrition, or cirrhosis. These and other observations described in this preliminary communication have served to raise the possibility of severe prealbumin deficiency being associated with alpha-1-antitrypsin deficiency, while the presence of low-but-not-absent PA in another Pi-D case might also suggest subgroup classification of the phenotype ZZ based on degrees of PA deficiency.

The fate of 14C-elastin in the peritoneal cavity of rats. I. Biochemical studies

Degradation of elastin was studied in rats after intraperitoneal implantation of a suspension of 14C-elastin that had been prepared by labeling bovine elastin with 14C-formaldehyde. Most of the degradation of 14C-elastin, measured by releasing the radioactivity in urine and feces, occurred between 6 and 15 days after the implantation. During this period an increase of leukocytes and macrophages in the implanted site was observed. This followed a brief increase in neutrophils. Furthermore, an elevation of the elastolytic activity, measured by the 14C-elastin, was found in cell lysates of both macrophages and neutrophils, which were recovered by lavage of the peritoneal cavity. But the enzymatic activity was not found in the cell-free lavage. On the contrary, there was elastase inhibitor in the lavage, increased by the implantation. The mechanism of the elastin degradation in the peritoneal cavity was discussed.

The induction of emphysema with elastase. II. Changes in connective tissue

Both clinical and experimental evidence implicate proteolytic enzymes active against elastin in the pathogenesis of emphysema. Paradoxically, however, the elastin content of emphysematous human lungs at autopsy has been normal. When emphysema was produced in hamsters by a single intratracheal injection of 25 units of porcine pancreatic elastase, the elastin content of the lungs was reduced from 1.40 +/- 0.22 mg. in controls to 0.43 +/- 0.10 mg. 24 hours after injection, and histologic sections showed that many elastic fibers had disappeared. The elastin content of the lungs gradually increased, approaching normal values by 2 months after injection. The incorporation of 14C-proline into elastin was markedly elevated during the first 2 weeks after injection, decreasing nearly to normal by 2 months. The synthesis of collagen was also increased, indicated by an increase in the collagen content of the lung, an increase in the prolyl hydroxylase activity, and an increase in incorporation of labeled proline into collagen. During the period of active resynthesis of elastin, small clumps of microfibrils and elastic fibrils were visible by electron microscopy within grooves on the surface of septal connective tissue cells in the lungs. Many elastic fibers seen in histologic sections up to 4 months after injection were of abnormal configuration and disorganized.