Effect of cartilage-derived factor on DNA and protein synthesis in cultured rat calvariae

Summary Cartilage-derived factor (CDF), a peptide closely related to the somatomedins, was studied for its effects on bone formation by examining the synthesis of DNA, collagen, and noncollagen protein in 24–96 h cultures of 21-day fetal rat calvariae. After 24 h of treatment, CDF at concentrations of 0.3–30 μg/ml caused a dose-dependent stimulation of the incorporation of³H-thymidine into DNA by 12–59%. The effect appeared and was maximal after 12 h, and was sustained for 96 h. CDF also increased the bone DNA content by 30–60%. After 24 h of treatment, CDF at 10–30 μg/ml had a small stimulatory effect on the incorporation of³H-proline into collagenase-digestible protein (CDP) and noncollagen protein (NCP). The effect on the labeling of CDP and NCP was sustained for 96 h. Cortisol decreased the stimulatory effect of CDF on DNA labeling but cortisol and CDF had an additive effect on the incorporation of³H-proline into CDP. The CDF stimulatory effect on the labeling of DNA, CDP, and NCP was seen in both the periosteum and periosteum-free calvaria. These studies indicate that CDF stimulates bone DNA, collagen, and noncollagen protein synthesisin vitro and may be a local regulator of bone growth.     

Proliferation and macromolecular synthesis by rat calvarial bone cells grown in various oxygen tensions

Perinatal rat calvarial bone cells were isolated by sequential collagenase digestion and grown in oxygen tensions ranging from 1 to 60% O2. Cell proliferation as determined by automated cell counting and DNA content was greatest in the lower oxygen tensions (less than or equal to 9% O2), whereas alkaline phosphatase activity and [35S]sulfate and [14C]proline incorporation were greatest in the higher oxygen tensions (greater than or equal to 13% O2). It is concluded that lower oxygen concentrations favor bone cell proliferation, whereas higher oxygen concentrations favor macromolecular synthesis. These findings, when related to the known pO2 of the fracture callus, suggest the following sequence of events: first, at the time of fracture an ingrowth of osteoprogenitor cells, capillary buds, and primitive mesenchymal cells occurs in the fracture site, a region of low pO2; second, a great increase in cellular proliferation accompanied by an initiation of macromolecular synthesis follows; finally, as the pO2 levels begin to increase, cellular proliferation decelerates, accompanied by an increase in macromolecular synthesis.     

Parathyroid hormone blocks the stimulatory effect of insulin-like growth factor—I on collagen synthesis in cultured 21-day fetal rat calvariae

We examined the interaction of parathyroid hormone (PTH) and recombinant human insulin-like growth factor I (IGF-I) on collagen synthesis in 21-day fetal rat calvariae as assessed by measuring the incorporation of [³H]proline into collagenase-digestible protein. After 96 hours of culture, 10 nM PTH antagonized the stimulation of collagen synthesis and partially blocked the increase in dry weight produced by 10 nM IGF-I. The effect of PTH to block IGF-I stimulated collagen synthesis was observed in the central bone of calvariae and was mimicked by forskolin and phorbol 12myristate 13-acetate, but not by 1,25-dihydroxyvitamin D₃, transforming growth factor- or dexamethasone. Our data are consistent with the concept that the direct effect of PTH is to inhibit basal CDP labeling and fully oppose IGF-I stimulated CDP labeling. The finding that this effect of PTH is mimicked by forskolin and PMA suggests that this block in IGF-I stimulation of CDP labeling involves both cAMP and protein kinase C mediated pathways.     

Effects of bone associated growth factors on DNA, collagen and osteocalcin synthesis in cultured fetal rat calvariae

Studies in bone and bone cell cultures have shown that osteocalcin synthesis is dependent on the maturity of the osteoblast and the presence of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3. The bone matrix is a rich source of growth factors that play a role in bone formation, but their effects on osteocalcin synthesis and their interactions with 1,25(OH)2D3 have not been examined. Insulin-like growth factor I (IGF I), basic and acidic fibroblast growth factor (bFGF and aFGF), platelet-derived growth factor (PDGF) and transforming growth factor beta (TGF beta), are growth factors associated with the bone matrix. These factors were shown to stimulate [3H]thymidine incorporation into DNA in 24 h cultures of fetal rat calvariae, and their effect was not modified by 1,25(OH)2D3. IGF I and TGF beta stimulated [3H]proline incorporation into calvarial collagen while the other growth factors studied did not; 1,25(OH)2D3 inhibited collagen synthesis in control as well as in IGF I and TGF beta treated calvariae. IGF I, bFGF and aFGF stimulated osteocalcin synthesis 1.5 to 2.5 fold but only IGF I was synergistic with the stimulatory effect of 1,25(OH)2D3. PDGF and TGF beta had no effect on osteocalcin synthesis. In conclusion, bone matrix-associated factors have important mitogenic effects in bone cultures, but only IGF I and FGFs stimulate osteocalcin synthesis, an effect that is of small magnitude when compared to that of 1,25(OH)2D3.     

The effects of prostaglandin E2 on DNA and collagen synthesis in osteoblastsIn Vitro

Summary The effects of prostaglandin E₂(PGE₂) on DNA and collagen synthesis in two separate cell populations were investigated. In view of their morphology, ALPase activity, DNA and collagen synthesis, and response to PGE₂, one population was in an undifferentiated state consisting of preosteoblast-like (PL) cells and the other was in a differentiated state consisting predominantly of osteoblastlike (OB) cells. As parameters of bone-forming activity, the incorporation of³H-thymidine into DNA and the incorporation of³H-proline into collagenase digestible protein were measured to assess DNA and collagen synthesis. The cells were treated with PGE₂ in the presence of indomethacin (IM) to avoid the influence of endogenous prostaglandins. At 24 hours, IM stimulated the DNA synthesis in both cell populations. Furthermore, a greater stimulation was found in the PL cells than in the OB cells. On the other hand, exogenously supplemented PGE₂ reversed the IM-induced stimulation of DNA synthesis. In contrast, high concentrations of PGE₂ alone increased the DNA synthesis. With respect to collagen synthesis, IM showed an inhibitory effect, especially in the PL cells. This inhibitory effect was also reversed by the addition of PGE₂. In addition to the stimulation of collagen synthesis, PGE₂ enhanced the proportion of protein synthesized as collagen. In the PL cells, the percentage of collagen synthesis was markedly decreased when cultured with IM for 48 hours. These results suggested that the effects of IM were mediated in part via its ability to reduce biosynthesis of prostaglandins, and that PGE₂ is a multifunctional autocrine regulator of bone formation.     

Temporal expression patterns of BMP receptors and collagen II (B) during periosteal chondrogenesis.

Articular cartilage has a limited ability to repair itself. Periosteal grafts have chondrogenic potential and are used clinically to repair defects in articular cartilage. An organ culture model system for in vitro rabbit periosteal chondrogenesis has been established to study the molecular events of periosteal chondrogenesis in vitro. In this model, bone morphogenetic protein-2 (BMP2) mRNA expression was found to be upregulated in the first 12 h. BMPs usually transduce their signals through a receptor complex that includes type II and either type IA or type IB BMP receptors. Receptors IA and IB play distinct roles during limb development. We have examined the temporal expression patterns for the mRNAs of these receptors using our experimental model. The mRNA expression patterns of these three BMP receptors differed from one another in periosteal explants during chondrogenesis. When these explants were cultured under chondrogenic conditions (agarose suspension with TGF-beta1 added to the media for the first 2 days), the expression of BMPRII mRNA and that of BMPRIA mRNA varied only slightly and persisted over a long time. In contrast, the expression of BMPRIB mRNAwas upregulated within 12 h, peaked at day 5, and fell to a level that was barely detected beyond day 21. Moreover, the expression of BMPRIB mRNA preceded that of collagen type IIB mRNAs, a marker for matrix-depositing chondrocytes. These data support a role for coordinate expression of BMP2 and its receptors early during periosteal chondrogenesis.     

Differentiation and mineralization in osteogenic precursor cells derived from fetal rat mandibular bone

Summary The process of mineralization in cells prepared either by neutral protease digestion (Pro I) or by collagenase digestion (fifth cycle, Col V) from fetal rat mandible was studied in vitro. Alkaline phosphatase (ALPase) activity of cells in Pro I was low on day 3, increased rapidly from day 8, and reached a maximum on day 16, whereas that in Col V was high on day 2, then declined and thereafter elevated to reach a maximum on day 13. Both cell populations synthesized type I collagen in cell matrix and medium. Type III collagen was observed in cell matrix of Pro I on day 14 and 21. There was ₂ band of type V collagen in cell matrix of Pro I on day 21. Calcium deposition could be detected from day 14 in Pro I and from day 19 in Col V. The von Kossapositive nodules were found on day 17 in Pro I and day 21 in Col V, respectively. The extracellular matrix in Pro I electron-microscopically consisted of well-banded collagen fibrils with a large number of calcified spherules. An elevation of ALPase activity, collagen synthesis, and mineral deposition occurred sequentially with a time lapse in Col V, and almost simultaneously in Pro I. The number of mineralized nodules was correlated with the density of plated cells in Pro I, but not in Col V. Dexamethasone caused an increase in the number of mineralized nodules in Pro I, but not in Col V, suggesting that Pro I contained osteoprogenitor cells. Thus, the mode of mineralization in cells derived from the mandible may differ depending on the presence of osteoprogenitor cells.     

Cerivastatin inhibits fetal calf serunvinduced DNA synthesis in cultured rat mesangial cells

SUMMARY: Inhibition of mevalonate synthesis by several statins has been shown to suppress DNA synthesis in glomerular mesangial cells. In the present study, we investigated the effect of a new statin, cerivastatin, on fetal calf serum (FCS)-induced DNA synthesis of cultured rat mesangial cells. Cultured rat mesangial cells were stimulated by 10% FCS in the presence or absence of cerivastatin and mevalonate. 5-bromo-2-deoxyuridine (BrdU) incorporation was used to assess DNA synthesis. the present study showed that 10% FCS caused marked stimulation of DNA synthesis in the mesangial cells. Cerivastatin inhibited FCS-stimulated BrdU incorporation in a dose-dependent manner. IC₅₀ was approximately 1 umol/L. Exogenous mevalonate, farnesyl pyrophosphate and geranylgeranyl pyrophosphate significantly prevented the inhibitory effect of cerivastatin on DNA replication. It appears that cerivastatin, by inhibiting the synthesis of mevalonate, may suppress DNA synthesis in the mesangial cells.     

The role of DNA synthesis in the responses of fetal rat calvariae to cortisol

To determine the extent to which the effects of cortisol on collagen synthesis in 21 day fetal rat calvariae are linked to its effects on cell replication, calvariae were cultured for 24-72 h with 0.1 and 1 microM cortisol in the presence or absence of 1 mM hydroxyurea (HU) or 30 microM aphidicolin (APC), inhibitors of DNA synthesis. The incorporation of [3H]proline into collagenase-digestible protein (CDP) and [3H]thymidine into DNA were measured during the last 2 h of culture. At 24 h HU and APC decreased thymidine incorporation by greater than 90%, and this remained low for the duration of culture. In contrast, cortisol reduced thymidine incorporation by only 44% at 72 h. Although cortisol caused a 24 h stimulatory effect and a 48 and 72 h inhibitory effect on CDP labeling and the percentage of collagen being synthesized (PCS), HU, and APC had no effect on basal CDP labeling or PCS over the 72 h culture period. Cortisol caused parallel alterations in the steady-state levels of alpha-1(I) procollagen mRNA, suggesting that its effects occur at the pretranslational level. At 24 h HU and APC did not prevent the stimulatory effect of cortisol on CDP labeling and PCS. At 48 h the inhibitory effects of cortisol on CDP labeling and PCS were observed in the presence of APC but not in the presence of HU. At 72 h the inhibitory effects of cortisol on CDP labeling and PCS were still observed in the presence of HU and APC.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of beraprost sodium on DNA synthesis in cultured bovine mesangial cells

Background This study was designed to investigate whether a stable analogue of prostacyclin, beraprost sodium, alters DNA synthesis in cultured bovine mesangial cells, and whether its action mediates that of endothelin-1 (ET-1). Methods Glomeruli were isolated from adult bovine kidneys, and cells were incubated in various combinations of beraprost sodium, fetal bovine serum, and BQ-123, an ET-1 receptor (ET-A) antagonist. For determination of the number of viable cells, cells were harvested with trypsin and subjected to the trypan blue dye-exclusion assay. Results Beraprost sodium caused 32% inhibition of basal ET-1 secretion and 43% inhibition of serum-stimulated ET-1 secretion at a concentration of 10⁻⁷ mol/L. In addition, BQ-123 significantly attenuated tritium-labeled thymidine ([³H]thymidine) incorporation into serum-stimulated mesangial cells. Finally, beraprost sodium (10⁻⁷ mol/L) caused 48% inhibition of [³H]thymidine incorporation into mesangial cells stimulated by ET-1. Conclusion These results suggest that prostacyclin can regulate DNA synthesis in cultured bovine mesangial cells, in part, by modulating ET-1 production and action.     

羧甲基壳多糖对瘢痕疙瘩成纤维细胞增殖和胶原合成的影响

目的 观察羧甲基壳多糖（carboxymethyl-chitosan，CM-CH）对体外培养的瘢痕疙瘩成纤维细胞（keloid fibroblasts，KFB）增殖和胶原合成的作用，探讨其治疗瘢痕疙瘩的机制。方法 采用四噻唑蓝（methylthiazoletrazolium，MTT）测定法和羟脯氨酸比色法（hydroxyproline，HP）测定不同浓度CM-CH作用KFB后对其增殖和上清液中胶原合成的影响。结果 CM-CH在10、50、100、200μg／ml作用KFB48、72h后，对KFB增殖有明显抑制作用（P〈0．05）。200μg／ml作用24、48、72h后，对KFB增殖抑制作用与曲安萘德组比较差异无统计学意义（P〉0．05）。CM-CH在10、50、100、200μg／ml对KFB作用48h后，能显著抑制该细胞胶原的合成（P〈0．01）。100、200μg／ml CM-CH抑制作用与曲安萘德组比较差异无统计学意义（P〉0．05）。结论 CM-CH对体外培养的KFB增殖和胶原合成有明显抑制作用，从而提示该物质治疗瘢痕疙瘩具有潜在前景。     

Effect of undernutrition on the chemical composition and the activity of alkaline phosphatase in soluble and particulate fractions of the rat calvarium and femur. II: Effect of preweaning undernutrition in the suckling rat

Summary We studied the effects of undernutrition during the suckling period on the development of the calvarium and the femur of rat pups suckling dams fed a 20% or 5% protein diet. The results show that the maturation of bone is delayed by undernutrition. In both the calvarium and the femur, the particulate fraction alkaline phosphatase reflects the rate increments in calcium and phosphorus uptake in control animals. This association is affected in the undernourished pups, as both the alkaline phosphatase activity in particulate fraction and the calcium and the phosphorus uptake decreased. However, the extent of disturbance was more prominent in the femur than in the calvarium, suggesting that during postnatal undernutrition the calvarium is less affected when compared to prenatal undernutrition, where the femur is less affected. The results from these studies suggest that proper nutrition is necessary for bone development during both the prenatal and postnatal period.     

Effect of multiplication-stimulating activity on DNA and protein synthesis in cultured fetal rat calvaria

Summary Multiplication-stimulating Activity (MSA), a peptide closely related to somatomedin, was examined for its effects on bone formation and sulfation activity in vitro. To study the effect of MSA on bone formation, we examined its effects on the incorporation of³H-thymidine into DNA,³H-uridine into RNA, and³H-proline into collagenase-digestible (CDP) and noncollagen protein (NCP), as well as DNA content in 21-day fetal rat calvaria cultured for 24 h periods. MSA caused a dose-dependent stimulation of the incorporation of³H-thymidine into DNA at concentrations of 1 to 3μg/ml, increased the total DNA content, and had no effect on³H-uridine incorporation. The effect on³H-thymidine incorporation appeared and was maximal at 12 h and was sustained for 24 h. After 24 h of treatment, MSA, 1 to 3μg/ml, caused a 25 to 60% stimulation on the incorporation of³H-proline into CDP and NCP. The effect was not specific for CDP, and there was no increase in the percent collagen synthesized. In contrast, insulin, 10 nM, increased the labeling of CDP by 95% but had a small effect on NCP and did not affect DNA synthesis. Insulin did not diminish the MSA effect on CDP and NCP labeling but slightly decreased its effect on thymidine incorporation. Cortisol inhibited DNA synthesis, but MSA was effective in its presence and cortisol did not affect the stimulatory effect of MSA on CDP or NCP. Histological sections showed a sixfold increase in the mitotic index after colcemid arrest in MSA-treated bones. MSA, 0.1 to 5μg/ml, also stimulated the incorporation of³⁵S into pig costal cartilage in culture. Our studies indicate that MSA stimulates DNA, collagen, and noncollagen protein synthesis in bone cultures and stimulates sulfate incorporation into cartilage.     

1,25-Dihydroxyvitamin D3 effects on collagen and DNA synthesis in periosteum and periosteum-free calvaria

1,25-dihydroxyvitamin D₃ [1,25(OH)₂D₃] is essential for normal growth and mineralization, but its direct effects on various aspects of bone formation remain controversial. 1,25(OH)₂D₃ was studied for its effects on DNA, collagen and noncollagen protein synthesis, and alkaline phosphatase activity (APA) in the periosteum and periosteum-free bone from 21-day fetal rat calvariae. 1,25(OH)₂D₃(0.01 to 10 nM) inhibited the incorporation of ³H-proline into collagenase-digestible protein (CDP) and the percent of collagen synthesized, and, at 10 nM, APA in the periosteum-free bone. 1,25(OH)₂D₃ inhibited type I collagen without affecting other collagen types. In contrast, 1,25(OH)₂D₃ at 10 nM caused a small but significant stimulation of the incorporation of ³H-thymidine into acid-insoluble residues (DNA) and on DNA content; both effects were exclusively observed in the periosteum. Hydroxyurea did not modify the inhibitory effect of 1,25(OH)₂D₃ on ³H-proline incorporation into CDP. These studies indicate that 1,25(OH)₂D₃ stimulates periosteal DNA synthesis but inhibits type I collagen synthesis and APA in the periosteum-free bone.     

苦参碱对人增生性瘢痕成纤维细胞合成胶原的影响

目的　研究苦参碱对人瘢痕成纤维细胞合成胶原的影响。方法　将苦参碱作用于体外培养的增生性瘢痕成纤维细胞 ,分别测定其分泌胶原、Ⅲ型前胶原、细胞内胶原含量。结果　苦参碱可减少瘢痕成纤维细胞分泌胶原、细胞内胶原和Ⅲ型前胶原的含量。结论　苦参碱在体外能明显抑制增生性瘢痕成纤维细胞胶原的合成     

Biphasic dose-response curves of cortisol effects on rat diaphyseal bone biomechanics

Summary Doses of 8, 16 (low), 32, 48, 64 (medium), and 150 (high) mg/kg/day of cortisol were administered to groups of 8 growing rats each during 16 days, and their femurs were then submitted to 3-point bending tests at low strain rate. Low doses had no effect. Medium doses, previously shown to improve calcium (Ca) balance and weight gain in the species, augmented diaphyseal elastic and ultimate strength, stiffness, and plastic-to-elastic deformation ratio with respect to untreated controls. This effect was achieved either by enhancing bone mass (volume, sectional moment of inertia, wall/lumen ratio) without changes in material quality parameters (32 mg/kg/day) or, conversely, by increasing bone tissue mechanical properties (stress, modulus of elasticity) not affecting bone geometry (48 and 64 mg/kg/day). The highest dose, known to depress Ca balance and weight gain, impaired diaphyseal mechanical performance in controls by substantially reducing bone mass without major variation in bone material properties, that is, developing a true osteopenic state in mechanical terms. The energy elastically absorbed per unit volume (proportional to the risk of comminute fractures) was greater with the highest dose because of enhanced deformability and diminished bone mass. The biphasic dose-response curves obtained, grossly parallel to those previously demonstrated for metabolic actions of cortisol in the same species, showed that biomechanical repercussion of this treatment on bone depends on different, dose-dependent effects which vary independently in temporal course, intensity, and sign.     

Effect of ascorbic acid on protein synthesis and collagen hydroxylation in continuous flow organ cultures of adult mouse periodontal tissues

Summary A continuous flow organ culture system (CFCS) was used to determine the effect of ascorbic acid on the synthesis of collagen and noncollagenous protein by bone of the alveolar process and periodontal ligament in organ cultures of adult mouse periodontium. For the last 24 h of 2 day cultures, 5 μCi/ml³H-proline was added to the medium. Highly purified collagenase was used to separate the collagenous and noncollagenous proteins and the incorporation of isotope into each fraction measured. Collagen synthesized in the presence of less than 10 μg/ml ascorbic acid was found to be highly under-hydroxylated (pro:hypro sp. acts. 2.3–3.1) in both tissues. When the ascorbic acid levels were between 25 and 100 μg/ml, the synthesis of collagenous proteins was selectively stimulated and hydroxylation significantly improved (pro:hypro sp. acts 1.72–1.89). The effect of ascorbic acid was not related to tissue viability since tissues cultured initially in the absence of ascorbic acid were able to recover completely when compared to controls given ascorbic acid continuously. The proportion of radioactivity in collagen and noncollagenous protein, collagen hydroxylation, and percentage of collagen synthesized as type III (av. 23%) in bone of the alveolar process was similar to that found in vivo. However, in the periodontal ligament in vitro the proportion of noncollagenous protein synthesized was increased from 70% to 87% and the percentage of type III collagen increased from 14% to 26% compared to in vivo results.     

当归挥发油对人脐静脉内皮细胞增殖、凋亡及Ⅲ型胶原合成的影响

目的探讨当归挥发油对人脐静脉内皮细胞增殖、凋亡和胶原合成的影响。方法体外培养人脐静脉内皮细胞，用噻唑蓝比色法检测细胞增殖活性，用流式细胞术分析细胞周期及凋亡，用放射免疫法测定胶原合成。结果低浓度（≤4mg／L）当归挥发油促进细胞增殖（P〈0．05），降低G0/G1期细胞且增加S期细胞（P〈0．05），降低凋亡率（P〈0．05），而高浓度（≥16mg／L）时抑制增殖（P〈0．05），增加G0/G1期细胞且减少S期细胞（P〈0．05），增加凋亡率（P〈0．05）。当归挥发油呈剂量和时问依赖性抑制细胞合成胶原（P〈0．05或0．01）。结论当归挥发油对人脐静脉内皮细胞的增殖呈低浓度刺激高浓度抑制的双向调节作用，但对胶原合成呈抑制效应。     

粉防己碱对瘢痕成纤维细胞DNA和胶原合成的影响

目的探讨粉防己碱对瘢痕成纤维细胞DNA和胶原合成的影响.方法以体外培养的人瘢痕成纤维细胞为实验模型,将粉防己碱(5～80mg/L)加入细胞培养液中进行干预并与对照组比较,用3H-TdR掺入法和3H-脯氨酸掺入法分别测定各组瘢痕成纤维细胞3H-TdR掺入值与3H-脯氨酸掺入值,以反映其DNA和胶原合成水平的变化.结果粉防己碱预处理浓度由5mg/L升至80mg/L时(1)瘢痕成纤维细胞3H-TdR掺入值(min-1)由对照组的1740±165分别降至1162±226、412±82,抑制率达76.32%,组间差异有非常显著意义(P＜0.01);(2)瘢痕成纤维细胞3H-脯氨酸掺入值(min-1)由对照组的1126±193分别降至535±141、341±89,抑制率达69.71%,组间差异有非常显著意义(P＜0.01).结论粉防己碱对体外培养的瘢痕成纤维细胞DNA和胶原合成具有抑制作用,呈剂量依赖关系,具有防治增生性瘢痕的应用前景.     

Triamcinolone impairs the synthesis of collagen and noncollagen proteins in condylar cartilage of newborn mice

Summary The effects of triamcinolone hexacetonide (TH) on the synthesis of collagen and noncollagen proteins were tested in mandibular condylar cartilage of newborn mice. Four-day-old ICR mice received a single i.p. injection of TH at doses ranging from 0.4 to 4.0 mg/kg body weight. Hydrocortisone, deoxycorticosterone, dexamethasone, and progesterone were administered at a dose of 4.0 mg/kg. Test animals and nontreated and vehicle-treated controls were sacrificed after 24, 48, and 72 hours and were processed for electron microscopy. Additional animals were injected with 5 μCi of³H-proline 2 hours before sacrifice. The specimens were extracted with 5% TCA containing 1 mM proline followed by 5% TCA, acetone, and ether, homogenized and digested with purified bacterial collagenase, and the amounts of radioactivity in collagenase digestible (CDP) and noncollagen proteins (NCP) were determined. The present results revealed that triamcinolone led to a significant dose-dependent decrease in the protein content of the tissue that lasted for 3 days (12–14% at the dose of 4 mg/kg). The incorporation of³H-proline into CDP was reduced by 39, 57, and 42% at 24, 48, and 72 hours, respectively whereas the incorporation into NCP was reduced by 20, 35, and 23%, respectively. When compared with other steroids, dexamethasone revealed a similar inhibitory effect, whereas hydrocortisone and deoxycorticosterone had no significant effect. Progesterone, on the other hand, showed a transient (24 hours) stimulatory effect on the synthesis of collagen synthesis (21%,P<0.05). Electron microscopy showed an atypical arrangement of collagen fibers and accumulation of large aggregates of collagen that filled the entire matrical space between cartilage cells.