Periosteal microcirculatory reactions in a zoledronate-induced osteonecrosis model of the jaw in rats.

OBJECTIVES: Nitrogen-containing bisphosphonates induce osteonecrosis mostly in the jaw and less frequently in other bones. Because of the crucial role of periosteal perfusion in bone repair, we investigated zoledronate-induced microcirculatory reactions in the mandibular periosteum in comparison with those in the tibia in a clinically relevant model of bisphosphonate-induced medication-related osteonecrosis of the jaw (MRONJ). MATERIALS AND METHODS: Sprague-Dawley rats were treated with zoledronate (ZOL; 80 i.v. µg/kg/week over 8 weeks) or saline vehicle. The first two right mandibular molar teeth were extracted after 3 weeks. Various systemic and local (periosteal) microcirculatory inflammatory parameters were examined by intravital videomicroscopy after 9 weeks. RESULTS: Gingival healing disorders (∼100%) and MRONJ developed in 70% of ZOL-treated cases but not after saline (shown by micro-CT). ZOL induced significantly higher degrees of periosteal leukocyte rolling and adhesion in the mandibular postcapillary venules (at both extraction and intact sites) than at the tibia. Leukocyte NADPH-oxidase activity was reduced; leukocyte CD11b and plasma TNF-alpha levels were unchanged. CONCLUSION: Chronic ZOL treatment causes a distinct microcirculatory inflammatory reaction in the mandibular periosteum but not in the tibia. The local reaction in the absence of augmented systemic leukocyte inflammatory activity suggests that topically different, endothelium-specific changes may play a critical role in the pathogenesis of MRONJ. CLINICAL RELEVANCE: This model permits for the first time to explore the microvascular processes in the mandibular periosteum after chronic ZOL treatment. This approach may contribute to a better understanding of the pathomechanism and the development of strategies to counteract bisphosphonate-induced side effects.

A novel method for in vivo visualization of the microcirculation of the mandibular periosteum in rats.

OBJECTIVE: The periosteum plays an important role in bone physiology, but observation of its microcirculation is greatly limited by methodological constraints at certain anatomical locations. This study was conducted to develop a microsurgical procedure which provides access to the mandibular periosteum in rats. METHODS: Comparisons of the microcirculatory characteristics with those of the tibial periosteum were performed to confirm the functional integrity of the microvasculature. The mandibular periosteum was reached between the facial muscles and the anterior surface of the superficial masseter muscle at the external surface of the mandibular corpus; the tibial periosteum was prepared by dissecting the covering muscles at the anteromedial surface. Intravital fluorescence microscopy was used to assess the leukocyte-endothelial interactions and the RBCV in the tibial and mandibular periosteum. Both structures were also visualized through OPS and fluorescence CLSM. RESULTS: The microcirculatory variables in the mandibular periosteum proved similar to those in the tibia, indicating that no microcirculatory failure resulted from the exposure technique. CONCLUSION: This novel surgical approach provides simple access to the mandibular periosteum of the rat, offering an excellent opportunity for investigations of microcirculatory manifestations of dentoalveolar and maxillofacial diseases.

Microcirculatory effects of selective endothelin-A receptor antagonism in testicular torsion.

PURPOSE: Testicular torsion without timely intervention causes incurable damage to the testis. We examined the causative role of microcirculatory injury in torsion induced testicular damage with particular regard to endothelin-A receptor activation. MATERIALS AND METHODS: The microcirculatory consequences of testicular torsion were assessed in the presence or absence of endothelin-A receptor antagonism in rats. Microcirculatory perfusion changes (red blood cell velocity and pulsatile flow pattern alterations) were examined by an orthogonal polarization spectral imaging technique. Microcirculatory inflammatory alterations were assessed by fluorescence intravital video microscopy after 60-minute torsion followed by 240-minute reperfusion. As a specific endothelin-A receptor inhibitor, the antisense homology box derived peptide ETR-p1/fl was applied 10 minutes before reperfusion. Tissue accumulation of leukocytes was estimated by myeloperoxidase activity in tissue biopsies taken at the end of the 4-hour reperfusion period. In further experiments testicular weight as a marker of permanent damage was evaluated 45 days after torsion. RESULTS: The physiological pulsatile flow pattern ceased in the initial phase of reperfusion while leukocyte-endothelial interactions increased throughout the examined reperfusion period. Endothelin-A receptor antagonism caused earlier return of pulsatile flow and recovery of red blood cell velocity, and alleviated microcirculatory inflammatory reactions and atrophy. CONCLUSIONS: Results suggest a pathophysiological role of endothelin-A receptor activation in the pathogenesis of testicular torsion. This effect is related to deterioration in testicular perfusion and activation of microcirculatory inflammatory reactions.

Neuroimmune interactions in Sjögren's syndrome: relationship of exocrine gland dysfunction with autoantibodies to muscarinic acetylcholine receptor-3 and mental health status parameters.

OBJECTIVES: Antimuscarinic acetylcholine receptor-3 (m3AChR) autoantibodies have been described in primary Sjögren's syndrome (pSS). The aim of this study was to compare various methods for their detection and to assess the contributions of anti-m3AChR and other immunological and psychosocial factors to the pathomechanism of secondary SS (sSS). METHODS: Sixty-five rheumatoid arthritis (RA) patients, 103 systemic lupus erythematosus (SLE) patients, 76 pSS patients and 50 controls were compared. Three immunodominant epitopes of m3AChR were synthesized and used in ELISA. Two extracellular epitopes were also prepared in fusion with glutathione-S-transferase and one in conjugation with bovine serum albumin. Mental health status was assessed with the 36-item Short-Form Health Survey and Functional Assessment of Chronic Illness Therapy fatigue scale. Correlations were evaluated between glandular function and anti-m3AChR positivities and specificities, features of SLE and RA, and mental health parameters. RESULTS: Fourteen RA and 27 SLE patients had sSS. The autoantibody levels to all epitopes of m3AChR were significantly higher in pSS and SLE patients than in the controls. The fusion protein forms discriminated RA from pSS and SLE; furthermore, the YNIP fusion protein also distinguished pSS from SLE. The prevalence and the mean levels of all autoantibodies did not differ statistically between sicca and non-sicca SLE or RA patients. Glandular dysfunction correlated with higher age in SLE and RA and an impaired health-related quality of life in SLE. CONCLUSIONS: The second and third extracellular loops of m3AChR are antigenic in pSS. Immunoassays with antigens as fusion peptides demonstrate the best performance. Sicca SLE patients have worse mental health status. Anti-m3AChR antibodies represent a peculiar example of neuroimmune interactions.

Limb ischemia-reperfusion differentially affects the periosteal and synovial microcirculation.

BACKGROUND: Joints are privileged compartments that enjoy increased protection against the inflammatory reactions affecting the extremities. We hypothesized that the functional characteristics of the microvasculature would contribute to the differential defensive potential of the synovial membrane. METHODS: We investigated the synovial microcirculatory reactions and compared them with those of the tibial periosteum in response to 60 min of total limb ischemia, followed by 180 min of ischemia-reperfusion (IR) in rats. Carrageenan/kaolin-induced knee monoarthritis, a neutrophil-driven synovial inflammation model, served as the positive control. RESULTS: IR brought about a significant reduction in red blood cell velocity in the capillaries and increases in rolling and adherence of the neutrophil leukocytes in the postcapillary venules (intravital microscopy), in adhesion molecule expression (intercellular adhesion molecule-1 immunohistochemistry) and in xanthine oxidoreductase activity in the periosteum. These changes were also pronounced in carrageenan/kaolin-induced monoarthritis but were almost completely absent in the synovium after the IR challenge. Most importantly, even after IR and in carrageenan/kaolin monoarthritis, the synovial microcirculation was characterized by significantly greater red blood cell velocities than that in the periosteum under resting conditions. CONCLUSIONS: The ischemic duration, which significantly affected the functional integrity of the periosteal microcirculation, did not bring about a marked deterioration in that of the synovial membrane, suggesting that the synovial microcirculation is less endangered to the consequences of short-term tourniquet exposure than the periosteum. The greater microcirculatory red blood cell velocities and lower IR-induced endothelial expression of intercellular adhesion molecule-1 in the synovial membrane might explain the greater resistance of this compartment to the inflammatory consequences of IR.

Effects of colloid solutions on ischemia-reperfusion-induced periosteal microcirculatory and inflammatory reactions: comparison of dextran, gelatin, and hydroxyethyl starch.

OBJECTIVE: To compare the microhemodynamics and possible anti-inflammatory reactions of colloid resuscitation with 4% gelatin, 6% dextran, or 6% hydroxyethyl starch 130/0.4 solutions. DESIGN AND SETTING: A randomized control in vivo animal study in a university research laboratory. ANIMALS: Adult male Wistar rats (280 +/- 20 g). INTERVENTIONS: Sodium pentobarbital-anesthetized animals were subjected to a 60-min complete hindlimb ischemia and a 180-min reperfusion. Volume resuscitation, either with a colloid (dextran, gelatin, or hydroxyethyl starch, 25 mL kg(-1) during 3 hr intravenously) or with lactated Ringer's solution, was initiated 10 min before reperfusion. Fluorescence intravital videomicroscopy was performed before ischemia and 30, 60, 120, and 180 min postresuscitation to quantify the tibial periosteal functional capillary density, the capillary red blood cell velocity changes, and leukocyte rolling and firm adherence in postcapillary venules. In a separate series blood samples were drawn to determine the release of soluble intercellular adhesion molecule-1 (enzyme-linked immunosorbent assay technique), and the surface expression of CD11b (flow cytometry) on peripheral blood granulocytes. MEASUREMENTS AND MAIN RESULTS: Reperfusion significantly increased the leukocyte rolling and firm adhesion (by 2.6 and 7.1-fold, respectively), evoked marked decreases in periosteal functional capillary density and red blood cell velocity (56% and 39%, respectively), and increased the CD11b expression on the circulating leukocytes (by 85%). Hydroxyethyl starch, but not gelatin or dextran pretreatment, significantly inhibited the firm adherence of the leukocytes and reduced the elevated CD11b expression. Hydroxyethyl starch pretreatment also effectively attenuated the decreases in functional capillary density and red blood cell velocity, whereas gelatin and dextran did not improve the microhemodynamics. Finally, ischemia had no direct effect on the soluble intercellular adhesion molecule-1 levels, whereas gelatin treatment increased significantly this parameter. CONCLUSIONS: When compared with gelatin or dextran solutions, hydroxyethyl starch provided a therapeutic advantage in this setting by exerting an inhibitory effect on the ischemia-reperfusion-induced local and systemic leukocyte reactions and the postischemic periosteal microvascular dysfunction.

Kupffer cell blockade improves the endotoxin-induced microcirculatory inflammatory response in obstructive jaundice.

Cholestasis predisposes to hypersensitivity to LPS, leading to potential septic complications. We set out to characterize the involvement of Kupffer cell (KC) activation in the hepatic microcirculatory and structural consequences of obstructive jaundice in the presence and absence of acute endotoxemia. The hepatic microcirculatory consequences of 3-day extrahepatic bile duct ligation (BDL) were assessed in rats. The contributions of changes in hepatic perfusion, leukocyte influx, and proinflammatory cytokine release to the development of hepatic structural damage were also determined. Furthermore, the corresponding consequences of BDL in combination with acute (2-h) endotoxemia (1 mg kg(-1) LPS, i.v.) were compared with those observed after LPS alone. In a second series, the same protocols were applied in identical groups of rats where the KC function was inhibited with 24-h gadolinium chloride pretreatment (10 mg kg(-1), i.v.). Bile duct ligation induced minor inflammatory reactions but caused a marked reduction in hepatic sinusoidal perfusion and severe histological damage. LPS treatment, however, elicited an approximately 5-fold increase in leukocyte adherence in the central venules and pronounced IL-6 and TNF-alpha release, but without significant structural damage. The combination of BDL with LPS enhanced the perfusion failure, leukocyte sticking/deposition, and proinflammatory cytokine release; most of these changes can be effectively ameliorated by gadolinium chloride. In conclusion, when obstructive jaundice is followed by a second hit of LPS, perfusion failure, liver inflammation, and structural damage are enhanced, the KCs playing a decisive role in this scenario. Therapeutic strategies aimed at KC blockade can potentially reduce the risk of inflammatory complications in cholestasis.

[Effects of phosphatidylcholine therapy after hindlimb ischemia and reperfusion]. / A foszfatidilkolin kezelés hatása kísérletes vegtag iszkémiát követoen.

BACKGROUND: Microcirculatory dysfunctions and mast cell reactions play important roles in hypoxic tissue injuries. The aims of this study were to characterize the effects of hindlimb ischemia-reperfusion on the periosteal microcirculation and to define the consequences of systemic phosphatidylcholine therapy during this condition. MATERIALS AND METHODS: Microcirculatory changes were visualized by means of fluorescence intravital videomicroscopy in anesthetized Wistar rats. 60 min of complete hindlimb ischemia was followed by a 180-min reperfusion in the presence of phosphatidylcholine treatment (50 mg/kg iv; in the second 10 min of reperfusion) or vehicle. Further two groups served as vehicle- or PC-treated sham-operated controls. The proportion of degranulated mast cells and the leukocyte accumulation (myeloperoxidase, MPO assay) were determined in muscle biopsies. RESULTS: Ischemia-reperfusion significantly increased the muscle MPO activity (from 14.94 to 63.45 mU/mg) and the proportion of degranulated mast cells (to 82.5%). The periosteal capillary red blood cell velocity (RBCV) and the functional capillary density (FCD) had decreased, while the primary and secondary leukocyte-endothelial cell interactions had increased by the end of reperfusion (rolling from 20.8 to 40.0%, and firm adherence from 254 to 872 mm-2). Phosphatidylcholine treatment decreased the leukocyte rolling and sticking, preserved the FCD and improved the RBCV The mast cell degranulation and MPO activity diminished significantly in the muscle layer. CONCLUSIONS: Mast cell degranulation accompanies ischemia-reperfusion-induced periosteal microcirculatory derangement. Systemic phosphatidylcholine treatment affords protection through ameliorating secondary inflammatory reactions.

Seasonal Monitoring of Cardiovascular and Antiulcer Agents' Concentrations in Stream Waters Encompassing a Capital City.

Nowadays monitoring pharmaceutical residues from surface waters is a widespread analytical task. Most of the studies are conducted from river waters or sewage treatment plants and mainly in Western Europe or North America. Such studies are seldom published from Eastern Europe, especially from stream waters, even though the prescription and consumption patterns of drugs as well as wastewater treatment procedures are very dissimilar. In Hungary the active substance of the most often prescribed drugs are cardiovascular and antiulcer agents. Hence in our study compounds belonging to these two groups were seasonally monitored in two main streams encompassing the Buda side of the Hungarian capital city and flowing into the Danube. To obtain data on the occurrence, fate, and seasonal variation of the compounds, samples were taken from altogether eleven points located near wastewater treatment plants and confluences. The results gave no identifiable pattern in the seasonal variation of concentrations but the contribution of the tributaries and wastewater treatment plants could be followed as expected. From the runoff corrected estuary concentrations the annual contribution of these streams to pharmaceutical pollution of the Danube could be estimated to be in excess of 1 kilogram for atenolol, famotidine, metoprolol, ranitidine, and sotalol.

Orthogonal polarization spectral imaging: a novel tool for examination of microcirculatory changes in the testis.

Testicular torsion is a surgical emergency in urologic practice. Many models have demonstrated the relationship between the degree and duration of the torsion and the subsequent damages of the testis, but there are as yet no suitable methods for visualization of the testicular microcirculation in this condition. We aimed to use orthogonal polarization spectral (OPS) imaging to observe the microcirculatory changes in the testis after ischemia-reperfusion (I/R) challenge, and to compare this technique with that of fluorescence intravital video microscopy (IVM). Twelve rats subjected to 60-minute ischemia following 720° testicular torsion were divided into two groups for IVM or OPS imaging examinations of the microcirculatory network of the testis at 60, 120, 180, and 240 minutes after reestablishment of perfusion. Significant microcirculatory failure was demonstrated after I/R in both groups. The absolute values of the microcirculatory parameters recorded with the OPS and IVM imaging methods did not differ statistically. The microcirculatory disturbances are present during the later phases of testicular torsion. OPS imaging technique represents an accurate noninvasive method to detect physiologic and pathophysiologic changes in the microcirculation of the testis.

Identification of phase I metabolites of cardiovascular and anti-ulcer drugs in surface water samples with liquid-chromatography-mass spectrometry methods.

In our study we have identified phase I metabolites of cardiovascular and anti-ulcer agents with the application of predictive multiple reaction monitoring (pMRM) methods with liquid-chromatography-triple-quadrupole mass spectrometry (LC-QQQ-MS) in surface water samples. Targeted accurate mass spectrometry measurements were also carried out for confirmation with liquid-chromatography-time-of-flight mass spectrometry (LC-TOF-MS). pMRM followed by a targeted accurate mass spectrometry measurement can provide a sound basis for the selection of metabolites to be included in analytical methods for the investigation of environmental load of pharmaceuticals. Using LC-QQQ-MS twenty-one metabolites could be identified with two independent transitions at the same retention time and six of them could also be confirmed with LC-TOF-MS.

Determination of antihypertensive and anti-ulcer agents from surface water with solid-phase extraction-liquid chromatography-electrospray ionization tandem mass spectrometry.

Pharmaceuticals are emerging contaminants in surface water and they must be measured to follow their effects on the aquatic environment. We developed a solid-phase extraction and liquid chromatography-electrospray ionization tandem mass spectrometry (SPE-LC-ESI-MS/MS) method for the determination of twenty-six pharmaceutical compounds - which belong to antihypertensive and anti-ulcer agents - from surface water samples. The selection of pharmaceuticals was based on usage frequency in Hungary. During method development Oasis HLB, SampliQ Polymer SCX and Si-SCX SPE cartridges were tested. As LC eluent ammonium formate, ammonium acetate buffers at pH 3 and 5 were investigated and for quantitation both matrix-matched and internal standard calibration was used. For matrix effect assessment post-extraction spike method was applied which can separate the extraction efficiency from ion suppression for better determination of recovery. Method detection limits (MDLs) varied between 0.2 and 10 ng/L. Precision of the method, calculated as relative standard deviation (RSD), ranged from 0.2 to 14.6% and from 1.2 to 22.4% for intra- and inter-day analysis, respectively. The method was applied to analyze Danube water samples. Measured average concentrations varied between 2 and 39 ng/L for eleven compounds and another one could be detected under LOQ.

Anti-inflammatory effects of limb ischaemic preconditioning are mediated by sensory nerve activation in rats.

We have shown that ischaemic preconditioning ameliorates both the local periosteal and the systemic leukocyte activation evoked by limb ischaemia-reperfusion. We hypothesized that the activation of chemosensitive afferent nerves by transient ischaemia contributes to the protective mechanisms of ischaemic preconditioning via a calcitonin gene-related peptide (CGRP)-dependent mechanism. In Sprague-Dawley rats, 60-min complete limb ischaemia was followed by 180 min of reperfusion. In further experiments, the CGRP analogue hCGRP (0.3 µg kg(-1)) or ischaemic preconditioning (2 × 10-min ischaemia/10-min reperfusion) was applied prior to the ischaemia-reperfusion insult. Ischaemic preconditioning was performed in three subgroups in which animals received the CGRP receptor antagonist CGRP(8-37) (30 µg kg(-1) h(-1)), the chemosensitive afferent nerve inactivator resiniferatoxin (3 × 15 µg kg(-1), sc), or vehicle. The effects of CGRP(8-37) and resiniferatoxin on ischaemia-reperfusion without ischaemic preconditioning were also evaluated. In the tibial periosteum of rats, intravital fluorescence microscopy and immunohistochemistry revealed significant attenuations of ischaemia-reperfusion-induced post-ischaemic leukocyte-endothelial interactions (rolling and adherence in the postcapillary venules) and tissue intracellular adhesion molecule expression following ischaemic preconditioning or hCGRP administration. Administration of CGRP(8-37) or pretreatment of animals with resiniferatoxin reversed the anti-inflammatory effects of limb ischaemic preconditioning, but failed to affect the microcirculatory consequences of ischaemia-reperfusion without ischaemic preconditioning. The results suggest that activation of the chemo- (capsaicin-) sensitive afferent nerves is involved in the mechanisms of microcirculatory anti-inflammatory protection provided by limb ischaemic preconditioning. Controlled activation of chemosensitive C-fibres or the CGRP receptors by the induction of ischaemic preconditioning or other means may furnish therapeutic benefit by ameliorating the periosteal microcirculatory consequences of tourniquet ischaemia.

Periosteal microcirculatory action of chronic estrogen supplementation in osteoporotic rats challenged with tourniquet ischemia.

AIMS: Transient ischemia of osteoporotic bones during elective orthopedic surgery or fracture repair carries risks for serious complications, and estrogen loss or replacement has a potential to influence ischemia-reperfusion-induced inflammatory activation. To clarify this, we investigated the periosteal inflammatory changes in a clinically relevant time frame in ovariectomized rats, an experimental model of postmenopausal bone loss. Furthermore, the effects of chronic estrogen supplementation on the postischemic local and systemic inflammatory reactions were assessed. MAIN METHODS: Bilateral ovariectomy or sham operation was performed in 3-month-old female Sprague-Dawley rats. Five months later, estrogen replacement therapy with 17ß-estradiol (20 µg(-1) kg(-1) day(-1)) or vehicle treatment was initiated. The microcirculatory inflammatory consequences of 60-min total hindlimb ischemia followed by 180-min reperfusion were examined 11 months after ovariectomy and were compared with those in 3-month-old animals. KEY FINDINGS: The osteoporosis that developed 5 months after ovariectomy was significantly ameliorated by estrogen replacement therapy. Both in ovariectomized and in non-ovariectomized animals, ischemia-reperfusion elevated the neutrophil adherence ~3-fold in the postcapillary venules of the periosteum (intravital microscopy), with an ~50-60% increase in intravascular neutrophil activation (CD11b; FACS analysis), an enhanced TNF-α release (ELISA) and periosteal expression of ICAM-1 (the endothelial ligand of CD11b; immunohistochemistry). Exogenous 17ß-estradiol considerably reduced TNF-α release and the number of neutrophil-endothelial interactions in the periosteum, without affecting the CD11b and ICAM-1 expression changes. SIGNIFICANCE: Osteoporosis itself does not increase the magnitude of the limb ischemia-reperfusion-associated periosteal inflammatory reaction. Chronic estrogen supplementation, however, reverses osteoporosis and significantly ameliorates the microcirculatory consequences of transient ischemia.

Ischemic limb preconditioning downregulates systemic inflammatory activation.

We examined local and systemic antiinflammatory consequences of ischemic preconditioning (IPC) in a rat model of limb ischemia-reperfusion (I-R) by characterizing the leukocyte-endothelial interactions in the periosteum and the expression of adhesion molecules playing a role in leukocyte-mediated inflammatory processes. IPC induction (2 cycles of 10 min of complete limb ischemia and 10 min of reperfusion) was followed by 60 min of ischemia/180 min of reperfusion or sham-operation. Data were compared with those on animals subjected to I-R and sham-operation. Neutrophil leukocyte-endothelial cell interactions (intravital videomicroscopy), intravascular neutrophil activation (CD11b expression changes by flow cytometry), and soluble and tissue intercellular adhesion molecule-1 (ICAM-1; ELISA and immunohistochemistry, respectively) expressions were assessed. I-R induced enhanced leukocyte rolling and adherence in the periosteal postcapillary venules after 120 and 180 min of reperfusion. This was associated with a significantly enhanced CD11b expression (by approximately 80% and 72%, respectively) and moderately increased soluble and periosteal ICAM-1 expressions. IPC prevented the I-R-induced increases in leukocyte adherence and CD11b expression without influencing the soluble and tissue ICAM-1 levels. The results show that limb IPC exerts not only local, but distant antiinflammatory effects through significant modulation of neutrophil recruitment.

Beneficial effects of phosphatidylcholine during hindlimb reperfusion.

BACKGROUND: Microcirculatory dysfunctions and mast cell (MC) reactions play important roles in hypoxic tissue injuries. The aims of this study were to characterize the effects of hindlimb ischemia-reperfusion (I-R) on the periosteal microcirculation and to define the consequences of systemic phosphatidylcholine (PC) therapy during this condition. MATERIALS AND METHODS: Microcirculatory changes were visualized by means of fluorescence intravital videomicroscopy in anesthetized Wistar rats. There was 60 min of complete hindlimb ischemia followed by a 180-min reperfusion in the presence of PC treatment (50 mg/kg i.v.; in the second 10 min of reperfusion) or vehicle. Further two groups served as vehicle- or PC-treated sham-operated controls. The proportion of degranulated MCs and the leukocyte accumulation (myeloperoxidase, MPO assay) were determined in muscle biopsies. RESULTS: I-R significantly increased the muscle MPO activity (from 14.94 to 63.45 mU/mg) and the proportion of degranulated MCs (to 82.5%). The periosteal capillary RBC velocity (RBCV) and the functional capillary density (FCD) had decreased, while the primary and secondary leukocyte-endothelial cell interactions had increased by the end of reperfusion (rolling from 20.8 to 40.0%, and firm adherence from 254 to 872 mm(-2)). PC treatment decreased the leukocyte rolling and sticking, preserved the FCD and improved the RBCV. The MC degranulation and MPO activity diminished significantly in the muscle layer. CONCLUSIONS: PC administration improves I-R-induced periosteal microcirculatory dysfunctions and ameliorates secondary inflammatory reactions. Systemic PC treatment could offer a potential treatment modality during hypoperfusion or inflammatory conditions of the bones.