Effects of ascorbate on insoluble elastin accumulation and cross-link formation in rabbit pulmonary artery smooth muscle cultures

Cultured pulmonary artery smooth muscle cells derived from the medial vessel layer of weanling rabbits were grown in the presence or absence of sodium ascorbate. The connective tissue elements insoluble elastin and collagen were identified and quantified. Formation and accumulation of alpha-aminoadipic acid gamma-semialdehyde (allysine) and the intermolecular cross-links desmosine (Des), isodesmosine (Ides), and aldol condensation product (Aldol) were evaluated from [14C]lysine pulse-chase experiments. [14C]Des, [14C]Ides, peptide-bound [14C]lysine, [14C]allysine, and [14C]Aldol were determined from amino acid analysis. The latter two components were determined after reduction with NaBH4. [14C]Proline conversion to hydroxy[14C]proline and collagenase susceptibility were used to identify and quantify collagen synthesis. Ascorbate dramatically affects insoluble elastin synthesis, accumulation, and cross-link formation. Cells grown in the presence of ascorbate synthesize and accumulate significantly less insoluble elastin than non-ascorbate cultures. Those elastin molecules which do become incorporated into the extracellular matrix in the presence of ascorbate contain a slightly elevated content of hydroxyproline and lysine and, most importantly, are turned over more rapidly.     

Tropoelastin production and tropoelastin messenger RNA activity. Relationship to copper and elastin cross-linking in chick aorta.

The elastin content of the chick thoracic aorta increases 2--3-fold during the first 3 weeks post-hatching. The deposition of elastin requires the covalent cross-linking of tropoelastin by means of lysine-derived cross-links. This process is sensitive to dietary copper intake, since copper serves as cofactor for lysyl oxidase, the enzyme that catalyses the oxidative deamination of the lysine residues involved in cross-link formation. Disruption of cross-linking alters tissue concentrations of both elastin and tropoelastin and results in a net decrease in aortic elastin content. Autoregulation of tropoelastin synthesis by changes in the pool sizes of elastin or tropoelastin has been suggested as a possible mechanism for the diminished aortic elastin content. Consequently, dietary copper deficiency was induced to study the effect of impaired elastin cross-link formation on tropoelastin synthesis. Elastin in aortae from copper-deficient chicks was only two-thirds to one-half the amount measured in copper-supplemented chicks, whereas copper-deficient concentrations of tropoelastin in aorta were at least 5-fold higher than normal. In spite of these changes, however, increased amounts of tropoelastin, copper deficiency and decreased amounts of elastin did not influence the amounts of functional elastin mRNA in aorta. Likewise, the production of tropoelastin in aorta explants was the same whether the explants were taken from copper-sufficient or -deficient birds. The lower accumulation of elastin in aorta from copper-deficient chicks appeared to be due to extracellular proteolysis, rather than to a decrease in the rate of synthesis. Electrophoresis of aorta extracts, followed by immunological detection of tropoelastin-derived products, indicated degradation products in aortae from copper-deficient birds. In extracts of aortae from copper-sufficient chicks, tropoelastin was not degraded and appeared to be incorporated into elastin without further proteolytic processing.     

Longitudinal gradients of collagen and elastin gene expression in the porcine aorta

The physical and chemical properties of the mammalian aorta are known to vary as a function of distance from the heart. These properties are highly dependent collagen and elastic fibers. In order to evaluate the mechanisms which regulate the accumulation of these two connective tissue proteins, gene expression was evaluated at both the biosynthetic and messenger RNA levels. Short-term (3 h) explant cultures of the medial portion of four segments of the descending aorta in newborn pigs were incubated in the presence of [3H] proline. Collagen production was quantified by collagenase digestion and elastin production was determined by immunoprecipitation. Between the conus arteriosus and the bifurcation of the iliac arteries, relative collagen synthesis increased 2-fold (from 5.8 to 12.0% of total protein synthesis), while relative elastin synthesis declined 10-fold (from 16.4 to 1.6% of total protein synthesis). Similarly, collagen production increased more than 7-fold (from 6.7 to 49.8 X 10(3) molecules/cell/h) while elastin production was reduced more than 3-fold (from 71.8 to 21.0 X 10(3) molecules/cell/h) along this developmental gradient. Elastin synthesis appeared to be controlled to a significant extent by the availability of elastin mRNA, since both cell-free translation and molecular hybridization to a cloned elastin gene probe showed gradients of elastin gene expression. Similarly, collagen synthesis was apparently regulated, at least in part, by an inverse gradient of collagen mRNA, as measured with a cloned cDNA for the pro-alpha 1(I) collagen gene. Marked changes in the amount of non-elastin protein synthesis accompanied differentiation and accounted for larger changes in relative synthesis. These results suggest that the phenotype of the cells of the porcine artery wall is distinct in different regions of this organ at this developmental stage.     

Capillary hemangioma (strawberry mark) of infancy: comparison of argon and Nd:YAG laser treatment

Capillary hemangioma of infancy (strawberry mark) is a self-limiting problem, and conservative treatment is recommended. These birthmarks can be associated with a great deal of morbidity. There is definitely a role for a palliative form of treatment without systemic complications or destruction of adjacent tissue. In a 6-year period, 55 patients received 57 Nd:YAG or argon laser treatments. Thirty patients received 31 argon treatments, and 25 patients received 26 Nd:YAG treatments; and 2 received first argon with subsequent Nd:YAG treatments. Although more dramatic successes were noted in the Nd:YAG laser, complications were more frequent and severe. Complications included delayed healing, postoperative bleeding, and some hypertrophic scarring. Complications were seen in 12 percent of all patients, 9 percent of these associated with the Nd:YAG laser.     

国产Nd:YAP激光组织热损伤效应的比较研究

目的:通过比较1 341 nm Nd:YAP与临床常用激光器脉冲Nd:YAG和连续Nd:YAG对皮肤、肌肉、静脉和肝脏组织的热损伤效应,了解Nd:YAP激光的作用特点,为其临床应用提供实验依据。方法:以大鼠作为实验对象,分为皮肤、肌肉组和静脉、肝脏组。皮肤、肌肉组:Nd:YAP激光、连续和脉冲Nd:YAG选择能量密度1000 J/cm2、2 000 J/cm2,静脉、肝脏组采用Nd:YAP激光和连续Nd:YAG两种激光器,能量密度选择500 J/cm2和1 000 J/cm2,对组织进行非接触式点状照射。照射过程中观察组织变化和损伤直径大小,并于照射后即刻、3天取材做病理切片,光镜下观察病理变化,比较相同能量密度下三种激光器对组织的热损伤和损伤修复情况。结果:皮肤、肌肉组:Nd:YAP激光在1 000 J/cm2条件下对组织的损伤以热凝固效应为主,2 000 J/cm2条件下组织发生明显气化、有一定的切割作用。相同能量密度下,脉冲Nd:YAP激光气化作用较两种Nd:YAG激光显著,而凝固损伤范围较连续Nd:YAG浅,较脉冲Nd:YAG深。肝脏、静脉组:Nd:YAP激光对肝脏的热凝固效应与Nd:YAG激光近似,气化作用明显;Nd:YAP激光对血管及其周围组织的凝固及气化作用均较连续Nd:YAG激光明显。结论:Nd:YAP激光具有良好的凝固与气化作用。     

Studies in vivo on the biosynthesis of collagen and elastin in ascorbic acid-deficient guinea pigs. Evidence for the formation and degradation of a partially hydroxylated collagen

1. After the administration of l-[G-(3)H]proline to guinea pigs deprived of ascorbic acid for increasing periods of time, the specific radioactivities of proline and hydroxyproline in skin collagen and aortic elastin were determined at various time-intervals after administration of the labelled compound with a view to studying the formation and degradation of collagen and elastin both deficient in hydroxyproline. 2. As judged from the incorporation of radioactivity into elastin proline, elastin synthesis was not decreased in the ascorbic acid-deficient animals. There was however, a rapid decline in the specific radioactivity of elastin hydroxyproline. The proline/hydroxyproline specific-radioactivity ratio was approx. 1.5:1 after 6 days and 20:1 after 12 days of ascorbic acid deprivation, in contrast with the ratio of 1:1 in controls. The results suggested that the effect of ascorbic acid deficiency on elastin biosynthesis could be regarded as simply an elimination of hydroxylation of elastin proline with the formation and retention of a polymer increasingly deficient in hydroxyproline. 3. Collagen proline and hydroxyproline specific radioactivities were derived from material that was soluble in hot trichloroacetic acid, non-diffusible and collagenase-degradable. In contrast with elastin, there was a rapid decline in the specific radioactivity of proline as well as hydroxyproline in collagen from the ascorbic acid-deficient animals. However, the proline/hydroxyproline specific-radioactivity ratio in all samples from scorbutic animals was consistently slightly above 1:1. The results suggest the appearance in place of collagen, but in rapidly diminishing amounts, of a partially hydroxylated collagen in which the degree of hydroxylation may be decreased only by approx. 10%. 4. Incorporation of radioactivity into the diffusible hydroxyproline in skin remained relatively high despite the rapid decline in the incorporation of radioactivity into collagen. This observation is interpreted as indicative of an increasing degree of degradation of partially hydroxylated collagen to diffusible peptides. An alternative explanation might be that partially hydroxylated peptides are released to an increasing extent from ribosomes before they attain a length at least sufficient to render them non-diffusible. In either case it implies the accumulation in scurvy of low-molecular-weight peptides enriched in proline and deficient in hydroxyproline and could explain the failure to accumulate a high-molecular-weight collagen deficient in hydroxyproline. 5. It is thought, however, that, in addition, an inhibition of ribosomal amino acid incorporation leading to decreased synthesis of partially hydroxylated collagen may also occur, perhaps secondarily to impaired hydroxylation.     

The synthesis of connective tissue protein in smooth muscle cells.

The synthesis of elastin by smooth muscle cells was clearly demonstrated by amino acid analyses and the presence of lysine-derived crosslinks. The values obtained were compatible with those found in amorphous elastin isolated from rabbit aortic tissue. Collagen synthesis by these same cells was monitored by the appearance of [14C] hydroxyproline when the cells were grown in the presence of [14C] proline. When the cells were pulsed with [14C] lysine, one could detect [14C] hydroxylysine and [14C] glucosylgalactosylhydroxylysine. Further evidence for the synthesis of elastin and collagen was the finding of radiolabelled epsilon-hydroxynorleucine and the reduced aldol condensate of two residues of allysine after reduction of [14C] lysine pulsed cells with NaBH4.     

Effects of amiodarone on elastin biosynthesis in primary hamster lung cell cultures

Amiodarone is a Class III antiarrhythmic agent that has been implicated as a cause of human pulmonary fibrosis. Pulmonary fibrosis is associated with increased levels of connective tissue proteins such as collagen and elastin. The purpose of this investigation was to determine whether elastin synthesis would be altered by in vitro amiodarone administration. Primary hamster lung cell cultures were utilized. Cultures were treated with 2, 10, and 20 micrograms/ml amiodarone. Following treatment, elastin synthesis was monitored by a biochemical tracer assay based on the presence of the cross-linking amino acids: desmosine/isodesmosine. These cross-links are found only in elastin. Addition of [14C] lysine to cultures results in uptake of the radiolabel into the cross-links. Cross-links were isolated and identified using chromatography and electrophoresis. At all doses of amiodarone, elastin synthesis was seen to increase above control levels. Light and electron microscopy confirmed the presence of an extracellular matrix. The morphologic studies also revealed the presence of cytoplasmic inclusion bodies and vacuoles that are often associated with cationic, amphiphilic drugs such as amiodarone.     

Enhanced arterial contractility to noradrenaline in diabetic rats is associated with increased phosphoinositide metabolism.

The purpose of this study was to investigate whether the increased contractile responsiveness of aortae from male rats with 12-14 week streptozotocin-induced diabetes to noradrenaline is associated with alterations in phosphoinositide metabolism. The contractile response to noradrenaline (10 microM) in both the presence and absence of extracellular calcium was significantly enhanced in aortae from diabetic rats. No significant differences were found between control and diabetic arteries in the basal incorporation of 32P and [3H]myo-inositol into phosphoinositides, or in the basal accumulation of [32P]phosphatidic acid and [3H]inositol phosphates. However, noradrenaline (10 microM) caused significantly greater breakdown of [32P]phosphatidylinositol 4,5-bisphosphate and formation of [32P]phosphatidic acid and [3H]inositol phosphates in diabetic aortae than in control preparations. The production of [3H]inositol phosphates induced by noradrenaline was selectively reduced by the alpha 1-adrenoceptor antagonist, prazosin, in both control and diabetic tissues. These results indicate that phosphoinositide metabolism in response to noradrenaline via stimulation of alpha 1-adrenoceptors is enhanced in aortae from chronic streptozotocin-diabetic rats. The increase in inositol 1,4,5-trisphosphate and 1,2-diacylglycerol production that presumably results could be responsible, at least in part, for the enhanced contractile response of aortae from diabetic rats to noradrenaline.     

Compartmentalization of proline pools and apparent rates of collagen and non-collagen protein synthesis in arterial smooth muscle cells in culture.

Rates of collagen and non-collagen protein synthesis in rabbit arterial smooth muscle cells (SMC) were determined by using the specific (radio)activity of [3H]proline in the extracellular, intracellular, and prolyl-tRNA pools. The intracellular free proline specific activity was only 25% of the extracellular value in cultures incubated for 12 h in 0.25 mM-proline. The specific activity of prolyl-tRNA was less than 10% of the extracellular specific activity. Increasing the extracellular proline concentration 10-fold (to 2.5 mM), while keeping the extracellular specific activity of proline constant, resulted in equilibration of the specific activities of intracellular and extracellular free proline, but the specific activity of prolyl-tRNA remained at less than 10% of the extracellular specific activity. Therefore, calculated rates of collagen and non-collagen protein synthesis were greatly underestimated using the intracellular or extracellular specific activity of proline. SMC were also incubated with 0.1 mM-[14C]ornithine in 0.25 nM or 2.5 mM non-labelled proline to examine synthesis de novo of proline and prolyl-tRNA from ornithine. In SMC cultures containing 0.25 mM unlabelled proline, the specific activity of intracellular ornithine was approx. 45% of the extracellular specific activity, due to the production of unlabelled ornithine. The specific activity of ornithine-derived intracellular free proline in SMC incubated with 2.5 mM-proline was significantly lower than in SMC incubated in 0.25 mM-proline, due to the influx of unlabelled proline. However, a corresponding difference in the specific activity of [14C]prolyl-tRNA between SMC in 0.25 mM- or 2.5 mM-proline was not observed. Ornithine-derived [14C]proline was incorporated into proteins in a manner different from that of exogenously added radiolabelled proline. A much higher proportion of the proline synthesized de novo was channelled into collagen synthesis relative to total protein synthesis. Together, these results show that intracellular proline pools are highly compartmentalized in arterial SMC. They also suggest that proline synthesized from ornithine may enter a prolyl-tRNA pool separate from that of proline entering from the extracellular medium.     

Nd^＋3：YAG激光对黑曲霉的诱变效应

本文采用Ｎｄ＾＋３：ＹＡＧ激光辐照柠檬酸生产菌黑曲霉孢子,辐照后进行培养和发酵试验,分析测定不同辐照时间黑曲霉孢子的存活率、黑曲霉菌丝体生长繁殖及颓丧 酸的速度、主要代谢产物柠酸的产量及淀粉糖化酶活力等变化。     

Adherence,proliferation and collagen turnover by human fibroblasts seeded into different types of collagen sponges

We describe an in vitro model that we have used to evaluate dermal substitutes and to obtain data on cell proliferation, the rate of degradation of the dermal equivalent, contractibility and de novo synthesis of collagen. We tested three classes of collagenous materials: (1) reconstituted non-crosslinked collagen, (2) reconstituted collagen that was chemically crosslinked with either glutaraldehyde, aluminium alginate or acetate, and (3) native collagen fibres, with or without other extracellular matrix molecules (elastin hydrolysate, hyaluronic acid or fibronectin). The non-crosslinked reconstituted collagen was degraded rapidly by human fibroblasts. Teh chemically crosslinked materials proved to be cytotoxic. Native collagen fibres were stable. In the absence of ascorbic acid, the addition of elastin hydrolysate to this type of matrix reduced the rate of collagen degradation. Both elastin hydrolysate and fibronectin partially prevented fibroblast-mediated contraction. Hyaluronic acid was only slightly effective in reducing the collagen degradation rate and more fibroblast-mediated contraction of the material was found than for the native collagen fibres with elastin hydrolysate and fibronectin. In the presence of ascorbate, collagen synthesis was enhanced in the native collagen matrix without additions and in the material containing elastin hydrolysate, but not in the material with hyaluronic acid. These results are indicative of the suitability of tissue substitutes for in vivo application.     

Nd:YAG laser radiation alters the proteolytic resistance of the liver tissue proteins in rats]

Small tissue strips were excised from rat liver and exposed to extensive irradiation with Nd:YAG laser followed by homogenization and spectrophotometric detection of 5% TCA-soluble protein fractions (oligopeptides) in both supernatants and 5NKOH-soluble sediments of the irradiated specimens. Trypsin along, or with chemotrypsin was added to the specimens to evaluate their proteolytic resistance during and after incubation for 24 h in the proteinase(s). The results showed that Nd:YAG laser irradiation resulted in significantly more oligopeptides following either schedule of the proteolysis employed in both supernatants and sediments as compared to the unaffected proteolytically tested specimens. At the same time a proteolytically resistant 5% TCA-insoluble fraction was elicited which belonged to proteins and, judging by the parallel ultrastructural data, was located in the cellular membranes. The probable mechanisms of the observed protein modifications, along with some pertinent clinical implications of Nd:YAG laser surgery, are considered.     

脱落酸高产菌的激光诱变效应研究

本实验对比紫外、 Ｈｅ Ｎｅ 激光、 Ｎｄ： Ｙ Ａ Ｇ 倍频脉冲激光对脱落酸产生菌的诱变效果。紫外诱变正变率为 ３８４％ ,负变率 ７６９％ ; Ｈｅ Ｎｅ 激光诱变正变率为 ５６％ ; Ｎｄ： Ｙ Ａ Ｇ 倍频脉冲激光诱变正变率为１９６％ 。 Ｎｄ： Ｙ Ａ Ｇ 倍频脉冲激光诱变辐照次数在 ４００ 次时效果较好,所得高产株效价提高率可达 ６０％ 以上     

Opposing effects of ascorbate on collagen and elastin deposition in the neonatal rat aorta

Ascorbic acid plays an important role in connective tissue metabolism, where, among other effects, it acts as a reducing factor in the reactions catalyzed by prolyl and lysyl hydroxylases. In vitro, ascorbic acid has been shown to have a positive influence on collagen synthesis at pre- and/or post-translational levels and a negative effect on elastin production. In the present work, the effects of vitamin C on extracellular matrix deposition have been studied in vivo. Stereological analysis on electron micrographs showed, compared to age-matched controls, a 50 to 60% increase of collagen deposition in the media and in the adventitia of the aorta of rats treated for 30 days from the 18th day of life with 10% ascorbate in their drinking water. By contrast, elastin volume density was significantly reduced by the treatment at all ages examined. These morphological data were supported by in situ hybridization observations showing enhanced collagen type I mRNA and reduced elastin mRNA expression upon treatment. Although vitamin C did not inhibit lysyl oxidase activity in vivo, being only slightly higher than in controls, enzyme activity was significantly reduced, when high doses of ascorbate were added in vitro. Lysyl oxidase activity may be a function of enhanced collagen metabolism rather than a direct effect of the vitamin on the enzyme activity. These data indicate that ascorbate exerts opposite effects on the deposition of two major components of the extracellular matrix in vivo, at least during periods of rapid growth.     

Bactericidal action of high-power Nd:YAG laser light on Escherichia coli in saline suspension

Infra-red light (1064 nm) from a high-power Nd:YAG laser caused more than 90% loss of viability of Escherichia coli during exposures that raised the temperature of PBS suspensions of the bacteria to 50 C in a thermocouple-equipped cuvette. In contrast, there was minimal loss of viability after heating the same suspensions to 50 degrees C in a water-bath, or in a PCR thermal cycler. The mechanism of laser killing at 50 degrees C was explored by differential scanning calorimetry, by laser treatment of transparent and turbid bacterial suspensions, and by optical absorbency studies of E. coli suspensions at 1064 nm. Taken together, the data suggested that the bactericidal action of Nd:YAG laser light at 50 degrees C was due partly to thermal heating and partly to an additional, as yet undefined, mechanism. Scanning electron microscopy revealed localized areas of surface damage on laser-exposed E. coli cells.     

Modulation of human dermal fibroblast extracellular matrix metabolism by the lymphokine leukoregulin

The effect of leukoregulin, a 50-kD lymphokine with unique antitumor properties, was studied in vitro on several fibroblast functions. Leukoregulin did not inhibit fibroblast proliferation, as measured by cell enumeration and [3H]thymidine incorporation, and had no cytotoxic effect in terms of increased membrane permeability detected by trypan blue exclusion, two of the major leukoregulin actions on tumor cells. Leukoregulin induced a dose-dependent decrease in collagen synthesis, demonstrated by decreased [3H]proline incorporation into collagenase-digestible protein, as early as 6 h after the addition of the lymphokine to human fibroblasts. Leukoregulin inhibited the synthesis of both type I and type III collagen, as measured by SDS-PAGE and by specific radioimmunoassay. Neutralizing antibodies to interleukin-1 alpha, interleukin-1 beta, tumor necrosis factor-alpha, and interferon-gamma failed to alter the effect of leukoregulin on collagen synthesis, attesting that leukoregulin action was not due to contamination by these cytokines. Inhibition of collagen synthesis occurred concomitantly with increased secretion of prostaglandin E2 and a transient rise in intracellular cyclic AMP content, peaking at 6 h. However, blocking prostaglandin synthesis with indomethacin did not counteract inhibition of collagen synthesis by leukoregulin, demonstrating independence of this action of leukoregulin from cyclooxygenase metabolites. Leukoregulin also stimulated glycosaminoglycan production in a dose-dependent manner, affecting the synthesis of hyaluronic acid as the major fibroblast-derived extracellular glycosaminoglycan. In addition, secretion of neutral proteases (collagenase, elastase, caseinase) was increased. These observations indicate that leukoregulin is able to regulate synthesis of molecules critical to the deposition of the extracellular matrix by nontransformed nonmalignant fibroblasts.     

The proteinase inhibitors leupeptin, pepstatin A, and TLCK cause reduced collagen production in freshly isolated embryonic chick fibroblasts in suspension culture

The production of [14C]proline-labeled collagen by embryonic chick tendon cells in suspension culture is reduced when the cells are incubated in the presence of lysosomotropic agents NH4Cl or chloroquine. Since these agents have multiple effects on fibroblasts, including inhibition of collagen secretion, specific proteinase inhibitors were tested for their effect on collagen production. Here the proteinase inhibitors N-p-tosyl-L-lysine chloromethylketone (TLCK) and leupeptin, specific for certain cysteine and serine proteinases, and pepstatin A, specific for aspartic proteinases, were tested for their effects on both the production and secretion of collagen. When treated with the proteinase inhibitor TLCK, the percentage of protein synthesis devoted to collagen decreased from control levels of 19.0 +/- 1.4% to 10.5 +/- 2.4% with 10 microM TLCK. Collagen synthesis was further reduced to only 1.2% of total protein synthesis with 100 microM TLCK. The incorporation of [14C]proline into collagenase-digestible peptides was only slightly decreased in the samples treated separately with 50 micrograms/ml leupeptin or 60 micrograms/ml pepstatin A. However, the production of collagen was reduced to 10.9 +/- 1.4% of total protein synthesis in samples treated with leupeptin and pepstatin A together. The basal intracellular degradation of newly synthesized, [14C]proline-labeled collagen was not significantly altered by any of the reagents tested, and secretion of the collagen which was produced was not impaired except in samples treated with 100 microM TLCK. The data presented are consistent with the hypothesis that a proteolytic mechanism utilizing some combination of cysteine, serine, and aspartic proteinases is necessary for continued collagen synthesis in freshly isolated embryonic chick tendon fibroblasts, and suggests that a heretofore unknown regulatory system may be operative in controlling the synthesis of collagen in fibroblasts.     

Effects of prostaglandin E1 on collagen production and degradation in human fetal lung fibroblasts

We examined the effects of prostaglandin E1 on the production and degradation of collagen in human fetal lung fibroblasts. Percentage collagen production was determined by incubating confluent cultures for 6 h with [3H]proline and either [14C]glycine or [14C]leucine and measuring the relative amounts of radioactivity incorporated into collagenase-sensitive and collagenase-insensitive material. Percentage collagen degradation was determined by measuring hydroxy[14C]proline in a low-molecular-weight fraction relative to total hydroxy[14C]proline. Prostaglandin E1, when present at a concentration as low as 0.25 micrograms/ml, reduced net collagen production by a factor of one-half, from 8 +/- 2 to 4 +/- 1% (P less than 0.05). In contrast, the change in percentage degradation was relatively gradual, rising steadily from the control value of 15 +/- 2 to 33 +/- 2% at 4 micrograms/ml (P less than 0.05). The increase in degradation, while significant, could not account for the total decrease in collagen production. We conclude that prostaglandin E1 exerts its inhibitory effect on collagen production in two essentially independent ways: lowering the rate of synthesis and increasing intracellular degradation. However, the decrease in synthesis is greater than the increase in degradation.