Effect of indomethacin on collagen metabolism of rat fracture callus in vitro

Phospholipases of mineralization competent cells and matrix vesicles: roles in physiological and pathological mineralizations

The present review aims to systematically and critically analyze the current knowledge on phospholipases and their role in physiological and pathological mineralization undertaken by mineralization competent cells. Cellular lipid metabolism plays an important role in biological mineralization. The physiological mechanisms of mineralization are likely to take place in tissues other than in bones and teeth under specific pathological conditions. For instance, vascular calcification in arteries of patients with renal failure, diabetes mellitus or atherosclerosis recapitulates the mechanisms of bone formation. Osteoporosis—a bone resorbing disease—and rheumatoid arthritis originating from the inflammation in the synovium are also affected by cellular lipid metabolism. The focus is on the lipid metabolism due to the effects of dietary lipids on bone health. These and other phenomena indicate that phospholipases may participate in bone remodelling as evidenced by their expression in smooth muscle cells, in bone forming osteoblasts, chondrocytes and in bone resorbing osteoclasts. Among various enzymes involved, phospholipases A₁ or A₂, phospholipase C, phospholipase D, autotaxin and sphingomyelinase are engaged in membrane lipid remodelling during early stages of mineralization and cell maturation in mineralization-competent cells. Numerous experimental evidences suggested that phospholipases exert their action at various stages of mineralization by affecting intracellular signaling and cell differentiation. The lipid metabolites—such as arachidonic acid, lysophospholipids, and sphingosine-1-phosphate are involved in cell signaling and inflammation reactions. Phospholipases are also important members of the cellular machinery engaged in matrix vesicle (MV) biogenesis and exocytosis. They may favour mineral formation inside MVs, may catalyse MV membrane breakdown necessary for the release of mineral deposits into extracellular matrix (ECM), or participate in hydrolysis of ECM. The biological functions of phospholipases are discussed from the perspective of animal and cellular knockout models, as well as disease implications, development of potent inhibitors and therapeutic interventions.

Effect of Non-Steroidal Anti-Inflammatory Drugs on Bone Healing

Nonspecific and COX-2 selective nonsteroidal anti-inflammatory drugs (NSAIDs) function by inhibiting the cyclooxygenase isoenzymes and effectively reduce pain and inflammation attributed to acute or chronic musculoskeletal pathologies. However, use of NSAIDs as an analgesic is thought to negatively contribute to bone healing. This review strived to provide a thorough unbiased analysis of the current research conducted on animals and humans regarding NSAIDs and their effect on bone healing. Specifically, this review discusses the role of animal models, dosing regiments, and outcome parameters when examining discrepancies about NSAIDS and their effects on bone regeneration. The role of COX-2 in bone regeneration needs to be better defined in order to further elucidate the impact of NSAIDs on bone healing.

The effect of ketoprophen on lumbar spinal fusion healing in a rabbit model. Laboratory investigation

OBJECT

Several reports have shown that nonsteroidal antiinflammatory drugs (NSAIDs) have an inhibitory effect in osteogenesis and reduce heterotopic ossification in humans. A deleterious effect of NSAIDs in posterolateral intertransverse process fusion has also been suggested. The authors used a validated rabbit model to try to determine the influence of the NSAID ketoprophen on the fusion rate in lumbar spinal arthrodesis.

METHODS

Thirty New Zealand male rabbits underwent posterolateral (intertransverse process) bilateral spinal fusions at a single level, using autologous bone graft obtained from both iliac crests. The animals were randomized after the operation, so that 15 rabbits received ketoprophen as a postoperative analgesic and the other 15 received the postoperative analgesic tramadol. The animals were killed 8 weeks after surgery, and fusion status was determined by inspection, palpation, anteroposterior radiographs, and histological analysis.

RESULTS

A solid fusion was obtained in eight rabbits (53%), and pseudarthrosis in seven rabbits (47%) in each group.

CONCLUSIONS

These findings suggest that the use of ketoprophen after intertransverse spinal fusion at a single level does not decrease the fusion rate, compared with tramadol.

Effect of COX-2 inhibitors and non-steroidal anti-inflammatory drugs on a mouse fracture model

A randomised, blinded, prospective animal study with 296 male C57BL/6N mice was performed to evaluate the biomechanical, biomolecular, biochemical, and histological impact of anti-inflammatory medications on fracture healing. A reproducible closed tibia fracture was created and stabilised with an intramedullary pin. Animals were randomised to placebo, ketorolac, ibuprofen, celecoxib, or rofecoxib treatment groups with biomechanical and biochemical testing at 4, 8, and 12 weeks. A second arm of the study was conducted in which animals were randomised to indomethacin or placebo treatment with biomechanical testing at 12 weeks. Histological and biomolecular studies were performed at 2 weeks on all groups in the first arm of the study. Biomechanical testing consisted of three-point bending evaluating maximum load, energy absorbed to maximum load, and stiffness. Safranin O-Fast Green stain was performed for histology. Biochemical quantifications of chondroitin and dermatan sulphate, hydroxyproline, total protein, and DNA content were performed. Osteocalcin and collagen types II and X were evaluated by in situ hybridisation. Some mechanical differences were seen between ketorolac and placebo at 4 weeks with respect to energy absorbed, but there were no differences in maximum load or stiffness seen between any treatment group and placebo at any time point. Indomethacin, celecoxib, rofecoxib, ibuprofen, and ketorolac did not significantly affect fracture healing in this young murine model.

Celecoxib does not affect osteointegration of cementless total hip stems

Celecoxib's effect on prosthetic osteointegration in patients undergoing total hip arthroplasty was studied. In a prospective, placebo-controlled, double-blind study of 49 patients, 24 were randomized to celecoxib (200 mg/d) and 25 to placebo over 6 weeks. Bone markers, N-teleopeptide, and bone-specific alkaline phosphatase were obtained postoperatively, and at 6 and 12 weeks. No radiographic prosthetic subsidence occurred. There were no significant differences from baseline in periprosthetic bone mineral density between the celecoxib and placebo groups at 3 and 6 months. There were no significant differences in baseline BSAlkP values between the 2 groups. At 6 and 12 weeks, average BSAlkP values increased. Urinary NTx concentrations followed a skewed distribution. Normalized NTx concentrations were statistically significantly greater in the celecoxib group than the placebo group at 6 weeks but not at 12 weeks.

Análise clínica e biomecânica do efeito do diclofenaco sódico na consolidação da fratura da tíbia no rato

Os AINH (Antiinflamatórios não hormonais) são agentes utilizados na prática clínica que interferem no processo inflamatório pela inibição da síntese de prostaglandinas e tromboxanos. Alguns trabalhos experimentais investigaram sua ação no processo de consolidação de fraturas, por meio de estudos clínicos e histológicos, sendo escassas as análises biomecânicas. Nesse estudo foram utilizados 20 ratos da linhagem Wistar, divididos aleatoriamente em dois grupos iguais: grupo A (controle) e grupo B (tratado com diclofenaco sódico). Em ambos os grupos foram realizadas fraturas abertas, após perfuração, na tíbia direita. A administração da droga foi via intramuscular, dose única diária, por 28 dias. Os animais foram pesados semanalmente. Após o sacrifício as tíbias foram dissecadas, pesadas e submetidas a ensaio biomecânico de flexão analisando-se carga máxima, deformação e coeficiente de rigidez. Observou-se que no grupo tratado com AINH não houve aumento do peso corpóreo a partir da segunda semana e as tíbias fraturadas foram mais pesadas. Neste grupo o calo ósseo suportou menor carga máxima, apresentando maior deformação e menor coeficiente de rigidez. Nos animais tratados, o osso não fraturado também se mostrou menos rígido. Concluiu-se, nas condições estudadas, que o DS alterou o processo de consolidação e o metabolismo ósseo, levando a retardo na maturação do calo e menor rigidez do osso intacto, respectivamente.

Simultaneous stimulation of EP2 and EP4 is essential to the effect of prostaglandin E2 in chondrocyte differentiation

OBJECTIVE

Prostaglandin E(2)(PGE(2)) has been reported to stimulate chondrocyte differentiation. However, the precise actions and signal transduction pathways of PGE(2)in cartilage are largely unknown. Our purpose is to identify which of the four PGE(2)receptor subtype(s), EP1-4, mediates the action of PGE(2)on chondrocyte differentiation.

DESIGN

We used primary chondrocytes derived from the resting zone of rat rib cartilage. The effects on chondrocyte differentiation were assessed by measuring the Alcian blue-stainable proteoglycan content and the expression levels of type II collagen mRNA by Northern blot analysis. The expression of the four PGE(2)receptor subtypes in rat primary chondrocytes was examined by reverse transcription-polymerase chain reaction.

RESULTS

PGE(2)stimulated the accumulation of proteoglycan and up-regulated the expression of type II collagen mRNA in primary chondrocytes. Dibutyryl cAMP, a cell-permeable analog of cAMP, an important intracellular mediator of PGE(2)signaling, also enhanced the expression of type II collagen mRNA and proteoglycan accumulation in chondrocytes. No EP agonist alone induced the expression of type II collagen mRNA. However, simultaneous administration of EP2 and EP4 agonists at high concentrations cooperatively induced the expression of type II collagen mRNA, mimicking the PGE(2)effect. The simultaneous stimulation of EP2 and EP4 also cooperatively enhanced proteoglycan accumulation and intracellular cAMP production. Moreover, an EP4 antagonist partially blocked the stimulatory actions of PGE(2)on the expression of type II collagen mRNA.

CONCLUSION

These results suggest that simultaneous stimulation of EP2 and EP4 is necessary and sufficient to elicit the effect of PGE(2)on rat primary chondrocyte differentiation.

Effect of tenoxicam on fracture healing in rat tibiae

BACKGROUND

Nonsteroidal anti-inflammatory drugs have been implicated in the development of delayed unions and nonunion after fractures in animal models. Previous investigations have identified two important factors as determinants of delayed fracture healing: early drug administration and a dose-dependent effect.

OBJECTIVE

The purpose of this investigation was to study the effect of tenoxicam, a nonsteroidal anti-inflammatory drug, on the fracture healing process in rat tibiae.

METHODS

Fifty-eight Wistar rats were randomly divided in four groups (I, II, III, and IV). Group I (control group, n=12) was given 0.1ml saline solution per day intramuscularly. Groups II (n=12), III (n=12), and IV (n=12) were administered 10mg per kg per day of tenoxicam intramuscularly. Administration of substances was begun on a week before to 48h after the fracturing procedure and continued during the entire experiment. Callus formation was studied histologically and histomorphologically, using light microscopy. In addition, a histologic grading based on the morphologic stage of fracture healing was carried out at 4 weeks, according to the criteria proposed by Allen et al.

RESULTS

There was a significant difference in treatment effect between Group I (saline solution) and Groups II, III, and IV (tenoxicam) (P=0.07). Histologically and histomorphologically, there were qualitative and quantitative delay in callus formation at all tenoxicam groups. This was more pronounced the earlier the nonsteroidal anti-inflammatory drug was started, although no significant difference could be detected between Groups II, III, and IV (P>(alpha=10%)). Four weeks after fracture, Group I (n=3) showed complete osseous union, Groups II (n=3) and III (n=3), complete cartilaginous union, and Group IV (n=3), incomplete osseous union, according to Allen et al. By using this rating scale, the difference between control and drug-treated groups was statistically significant (P<0.1).

CONCLUSION

Under studied conditions, this investigation shows that administration of tenoxicam intramuscularly delays fracture healing process in rat tibiae. These results suggest the hypothesis that early drug administration may delay bone healing after experimental fractures in animals, although it could not be detected statistically significant.

COX-2 selective NSAID decreases bone ingrowth in vivo

Whether non-steroidal anti-inflammatory drug (NSAID)-induced suppression of bone ingrowth is due to cyclooxygenase-1 (COX-1) inhibition, cyclooxygenase-2 (COX-2) inhibition, or through a yet unidentified pathway is unknown. In this study, the effects of a non-specific COX-1 and COX-2 inhibitor, versus a specific COX-2 inhibitor on bone ingrowth and tissue differentiation are examined in vivo. Harvest chambers were implanted unilaterally in the tibiae of eight mature, New Zealand white rabbits. After a 6-week period for osseointegration of the chamber, the following oral treatments were given for 4 weeks each, followed by a harvest in each case: drinking water with no NSAID (control 1), Naproxen sodium--a COX-1 and COX-2 non-specific inhibitor at a dose of 110 mg/kg/day in the drinking water, drinking water with no NSAID (control 2), and Rofecoxib-a COX-2 inhibitor at a dose of 12.5 mg/day inserted directly into the rabbit's mouth. Harvested specimens were snap frozen, cut into serial 6 microm sections and stained with hematoxylin and eosin for general morphological characterization, and alkaline phosphatase (osteoblast marker). Sections were also processed for immunoperoxidase staining using monoclonal antibodies to identify cells expressing the vitronectin receptor (osteoclast-like cells). With drinking water alone, the percentage of bone ingrowth averaged 24.8 +/- 2.9% and 29.9 +/- 4.5% respectively. Naproxen sodium in the drinking water and oral Rofecoxib decreased bone ingrowth significantly (15.9 +/- 3.3%. p = 0.031 and 18.5 +/- 2+/-4%, p = 0.035 compared to drinking water respectively). Both Naproxen sodium (p = 0.026) and Rofecoxib (p = 0.02) decreased the number of CD51 positive osteoclast-like cells per section compared with drinking water alone. Rofecoxib decreased the area of osteoblasts per section area (p = 0.014) compared to controls, although the value for Naproxen sodium did not reach statistical significance. The results of the present study suggest that bone formation is suppressed by oral administration of an NSAID which contains a COX-2 inhibitor. COX-2 inhibitors currently taken for arthritis and other conditions may potentially delay fracture healing and bone ingrowth.

Cyclo-oxygenase 2 function is essential for bone fracture healing

Despite the molecular and histological similarities between fetal bone development and fracture healing, inflammation is an early phase of fracture healing that does not occur during development. Cyclo-oxygenase 2 (COX-2) is induced at inflammation sites and produces proinflammatory prostaglandins. To determine if COX-2 functions in fracture healing, rats were treated with COX-2-selective nonsteroidal anti-inflammatory drugs (NSAIDs) to stop COX-2-dependent prostaglandin production. Radiographic, histological, and mechanical testing determined that fracture healing failed in rats treated with COX-2-selective NSAIDs (celecoxib and rofecoxib). Normal fracture healing also failed in mice homozygous for a null mutation in the COX-2 gene. This shows that COX-2 activity is necessary for normal fracture healing and confirms that the effects of COX-2-selective NSAIDs on fracture healing is caused by inhibition of COX-2 activity and not from a drug side effect. Histological observations suggest that COX-2 is required for normal endochondral ossification during fracture healing. Because mice lacking Cox2 form normal skeletons, our observations indicate that fetal bone development and fracture healing are different and that COX-2 function is specifically essential for fracture healing.

Pathophysiology of delayed healing

Delayed union represents an ongoing failure of initial fracture management. It still occurs partly because the precise reason why a patient's fracture does not heal frequently is unknown. This article aims to outline the limited material available on the pathophysiology of delayed healing. The systemic status of the patient, local limb status before injury, the nature of the traumatic injury, local host response to the injury, potential negative impact of orthopaedic fracture care, and pharmacologic variables are considered.

The effects of nonsteroidal anti-inflammatory drugs on posterior spinal fusions in the rat

STUDY DESIGN

This was a prospective study to determine the potential effects of indomethacin on spinal fusions in the rat.

OBJECTIVES

To determine if indomethacin exerts a deleterious effect on spinal fusions in the rat model.

SUMMARY OF BACKGROUND DATA

Nonsteroidal anti-inflammatory drugs are a class of compound that affect bone osteogenesis during fracture healing and heterotopic ossification. Spinal fusion is a process that occurs via osteogenesis and, therefore, may be similarly affected.

METHODS

Thirty-nine adult, Sprague-Dawley rats underwent a three-level posterior spinal fusion. Fusion was performed using morselized autogenous vertebral bone graft obtained via caudectomy and stabilized using a cerclage wiring technique. The 39 rats were divided into two groups consisting of 17 study animals and 22 control animals. The control group was injected with 1.5 cc of 0.9 normal saline subcutaneously for 12 weeks, whereas the test animals were injected on an identical schedule using 3 mg/kg of indomethacin sodium salt. Two control animals died, and three animals in the treatment group died of drug-related complications. Twelve weeks after surgery, all animals were killed, and the involved spinal segments were evaluated by direct manual examination. A fusion was probable if the spinal segments exhibited decreased scaled micromotion.

RESULTS

Sixty segmental levels in 20 control animals were assessed. Overall, 27 of 60 levels (45%) achieved fusion. In the indomethacin-treated group, 42 levels in 14 animals were evaluated. Overall, four of 42 levels (10%) achieved a fusion. Chi-square analysis demonstrated a significant difference (P < 0.001) between the control and indomethacin-treated groups.

CONCLUSIONS

This study raises serious questions about the inhibitory effects of nonsteroidal anti-inflammatory drugs on spinal fusion. Clinically, the widespread use of nonsteroidal anti-inflammatory drugs in the postoperative period after spinal fusion may need to be avoided.

Prostaglandin release from rat femurs after implantation of hydroxylapatite and aluminium oxide ceramics

The bony reaction after implantation of uncemented ceramics is of special interest. Therefore porous and dense hydroxylapatite and aluminium oxide ceramics were implanted in rat femurs. One group received no surgical manipulation and another with a sham procedure where no ceramics were implanted served as controls. After 6 and 10 days the rat femurs were harvested and the release of PGE2 and 6-keto-PGF1 alpha was measured with specific radioimmunoassays. Decrease in the release of PGE2 from day 6 to day 10 was present in all three implants. In contrast, 6-keto-PGF1 alpha increased from day 6 to day 10. Comparing the ceramic types an increase in 6-keto-PGF1 alpha release was seen in the porous hydroxylapatite group. These prostaglandin (PG) release patterns after ceramic implantation are similar to those of fracture healing, but aluminium oxide seems to be inert, while hydroxylapatite, especially the porous type, stimulates 6-keto-PGF1 alpha release.

Quantitative analysis of angiogenesis and growth of bone: effect of indomethacin exposure in a combined in vitro-in vivo approach

Nonsteroidal anti-inflammatory agents have been used experimentally and clinically to suppress a variety of physiological events, including angiogenesis and formation of bone. The exact mechanisms by which indomethacin alters skeletal tissue generation are unknown, due in part to methodological limitations. By the use of an organ culture assay and an animal model using intravital microscopy in mice bearing dorsal skinfold chambers, the effect of indomethacin on growth and angiogenesis of neonatal femora was characterized over 16 days. In both assays, femora significantly elongated with time (P < 0.05). The in vitro growth rate was more rapid than in vivo and dependent on the serum concentration, culture medium and age of mice. Although enhancing the serum content promoted cellular proliferation in organ culture, it dose-dependently suppressed femoral elongation, leading at 20% fetal calf serum to growth rates identical to those observed in vivo. Indomethacin supplementation (2 and 10 mg l-1) significantly accelerated longitudinal femoral growth in organ culture (P < 0.05), whereas in vivo indomethacin (2 mg kg-1) did not modulate either angiogenesis or elongation of bone. Our in vitro data propose a central role of serum in the regulation of bone formation. Although indomethacin altered femoral growth in vitro, our findings do not suggest that indomethacin suppresses angiogenesis or growth of bone in vivo. The complexity of physiological events in vivo may be obscuring a detectable effect.

Influence of indomethacin on bone turnover related to orthodontic tooth movement in miniature pigs

The purpose was to evaluate the influence of a prostaglandin inhibitor, indomethacin, on the tissue reaction related to orthodontic tooth movement. Sixteen miniature pigs were chosen for the study, eight of which received indomethacin perorally every day of the 39-day observation period. Sentalloy expansion springs (GAC, Central Islip, N.Y.) delivering 100 cN were inserted on a segmented arch between the central lower incisors. Intravital labeling with tetracycline was used for the evaluation of the rate of bone formation. After the pigs were killed, the bone turnover was evaluated on undecalcified methacrylate embedded sections and on microradiographs. The histomorphometric analysis of bone turnover revealed that the relative extent of resorption surfaces was decreased significantly in the indomethacin treated animals. Formation surfaces were also decreased although not significantly. The bone turnover, but not the mineralization rate, was influenced. The results corroborate the recommendation that prostaglandin inhibitors should be avoided during orthodontic treatments.

Release of prostaglandins from bone and muscle after femoral osteotomy in rats

In rats after nonstabilized femoral osteotomies, the changes in the release of prostaglandins (PGs) during bone healing (from bone and surrounding muscle tissue) were determined for PGE2, PGF2 alpha, 6-keto-PGF1 alpha, and thromboxane B2. A unilateral osteotomy, with contralateral soft-tissue dissection, was performed. After 4 or 10 days, the rats were killed and soft tissue and femoral bone were incubated, and the release of PGs was measured with specific radioimmunoassays. The release of PGs from rat femurs without previous surgery and from the sham-operated on side did not differ after 180 minutes' incubation. The release of PGE2, 6-keto-PGF1 alpha, and thromboxane-B2 from the osteotomy site was increased for bone on Day 4 and for muscle on Day 10 when compared with the controls. The release of PGF2 alpha from bone and muscle was about the same on both days, but increased as compared with the controls on Day 10 for bone. On Day 10, the other PGs for muscle and bone tissue were decreased as compared with Day 4. The most pronounced release of PGs occurred during the early healing phase after osteotomy; as early as 10 days after surgery, most of the PGs were not increased when compared with the sham-operated on side.

Gene expression of fibroblast matrix proteins is altered by indomethacin

The role of indomethacin in the regulation of extracellular matrix synthesis was studied in dermal fibroblast cultures. Indomethacin (10 microM) blocked totally the prostaglandin secretion and markedly increased the synthesis of collagen. In parallel, measurement of fibronectin, type I and type III procollagen mRNA levels showed a substantial increase under the action of indomethacin. On the other hand, indomethacin did not modify the mRNA levels of dermatan sulfate proteoglycan core protein. Measurement of collagen production estimated as the amount of collagenase digestible protein and by specific radioimmunoassay indicated a good correlation with the corresponding mRNA levels. These results suggest that indomethacin can regulate the extracellular matrix deposition at a transcriptional level.

Uncertain effect of indomethacin on physeal growth injury. Experiments in rabbits

Growth arrest and shortening remain significant sequelae of growth-plate injuries. Nonsteroidal anti-inflammatory agents, known to inhibit callus and bone formation, may be useful to diminish callus-induced growth effects after epiphyseal fracture. In this study, we created a longitudinal osteotomy of the medial distal femoral condyle in 54 rabbits to model a Type IV epiphyseal fracture. We treated half with indomethacin and half with normal saline for 6 weeks. Nineteen animals of each group developed deformity, with indomethacin-treated animals averaging only slightly less angulation than the controls. However, the mean femoral shortening was less in the indomethacin-treated animals as compared with the controls.

The influence of indomethacin on biomechanical and biochemical properties of the plantaris longus tendon in the rabbit

It has previously been reported that indomethacin inhibits fracture healing and heterotopic bone formation. Stimulated by these reports, we undertook the present investigation to study the influence of indomethacin on biomechanical and biochemical properties of the plantaris longus tendon in the rabbit. Sixty-eight New Zealand White rabbits were used for the experiment. Half of them were treated with indomethacin, 10 mg/kg orally a day, and the other half with placebo. After 4, 8, and 16 weeks of treatment biomechanical and biochemical variables were determined and compared between the two groups. After 16 weeks there was a significant increase in tensile strength in the group treated with indomethacin. There was no certain concomitant change in the total collagen content, the amounts of soluble and insoluble collagen, or the water content. Further investigations concerning the influence of indomethacin on tendon healing are indicated.

The influence of indomethacin on tendon healing. A biomechanical and biochemical study

The influence of indomethacin on the biomechanical and biochemical properties of tendons during their healing was investigated. In 68 New Zealand White rabbits a transverse tenotomy followed by repair with a criss-cross suture was performed in the plantaris longus tendon of the left hind limb. The leg was immobilized for 4 weeks postoperatively in a long-leg plastic splint. Half of the animals were treated with indomethacin, 10 mg/kg/day orally, and the other half with placebo. After 4, 8, and 16 weeks of treatment the animals were killed and biomechanical and biochemical parameters were measured. After 16 weeks there was a significant increase in tensile strength in the indomethacin group. There were only small biochemical differences between the groups. However, there was a slight but significant decrease in the amount of soluble collagen in the indomethacin group. This may indicate a higher degree of cross-linkage following indomethacin treatment, which might explain the increased tensile strength.

Effects of acetylsalicylic acid and naproxen on the synthesis and mineralization of collagen in the rat femur

The influence of acetylsalicylic acid (ASA) and naproxen on the biochemical properties of intact growing femora in young male rats was studied. The medication periods were 9 and 18 days. At an ASA dose of 150 mg/kg/12 h the rate of collagen synthesis and the rate of mineral incorporation decreased and were impaired by about 10% compared with controls after 18 days. The dry weights and contents of collagen and calcium were not influenced after 9 days, but were reduced by 4%-7% after 18 days. A higher solubility of collagen (7%) was also found at the end of the study. In rats that received ASA at 100 mg/kg/12 h no significant differences were observed. A naproxen dose of 20 mg/kg/12 h reduced the rate of mineral deposition after 18 days, but had no other detectable effects on bone. The results indicate that ASA inhibits bone formation.

A histometric study of the effect of indomethacin and calcitonin on bone remodelling in hamster periodontitis

The action on bone remodelling of indomethacin, a potent inhibitor of prostaglandin (PG) synthesis, was determined in hamster periodontitis and compared to that of calcitonin. The two treatments reduced the extent of bone resorption considerably but not significantly (NS). The reversal phase, the intermediate step between resorption and formation, was decreased by 33 per cent (NS) by indomethacin and 75 per cent by calcitonin (p less than 0.02). Bone formation was increased by 270 per cent with indomethacin (p less than 0.05) and by 400 per cent with calcitonin (p less than 0.03), compared with untreated animals. This exceeded the extent of bone formation activity in control animals. These data strongly suggest that PG are involved in the mechanism of bone destruction in hamster periodontitis and that PG are potent in vivo uncouplers of bone remodelling as they participate both in an increase in bone resorption and a decrease in bone formation. A partial decrease in reversal lacunae indicates that other factors, also acting as uncouplers, probably take part in the mechanism of bone destruction.

Effect of indomethacin and naproxen on the metabolism of collagen in adjuvant-induced arthritis

The effect of indomethacin and naproxen on collagen metabolism was studied in arthritic animals after an injection of [3H]-proline, both the specific and total radioactivity of [3H]-hydroxyproline being determined in skin collagen fractions and in urine. It was found that collagen synthesis and conversion of soluble to insoluble collagen are diminished, accompanied by an increased collagen degradation in untreated arthritic animals. Administration of indomethacin and naproxen to arthritic animals accelerated the synthesis of collagen and conversion soluble to insoluble collagen and inhibited the catabolism of collagen.

Indomethacin and aspirin: effect of nonsteroidal anti-inflammatory agents on the rate of fracture repair in the rat

A total of 210 male Charles River CD rats, 45 days old, were subjected to a fracturing of the right radius and ulna by digital pressure while under ether anesthesia. These animals were then assigned randomly to dose groups (1, 2 or 4 mg/kg/day of indomethacin and 100, 200, or 300 mg/kg/day of aspirin) and were dosed for 21 days. Dose levels were chosen to provide approximately equipotent levels of the test compounds with the highest dose approaching toxicity. Radiographs were taken of control-rat fractures on days 8, 14, and 21. Three rats at 4 mg/kg/day of indomethacin died of interstinal perforation prior to scheduled sacrifice. On day 22, all remaining rats were sacrificed by exsanguination under anesthesia. Histologic secretions of the radius and ulna were examined in random sequence without knowledge of the treatment regimen. A histologic grade based on the morphologic stage of fracture healing was given. There was a drug- and dose-related retardation of fracture healing, which was statistically significant at all dose levels of indomethacin and the highest level of aspirin, as compared to controls. Decreased mean grades in the groups given 100 and 200 mg/kg/day of aspirin, though not statistically significant, suggest a retarding effect on fracture healing at these levels also. No statistically significant changes in numbers of pseudoarthroses were found.