Changes in microcirculation of small intestine end-to-end anastomoses in an experimental model.

INTRODUCTION: Sufficient perfusion is essential for a safe intestinal anastomosis. Impaired microcirculation may lead to increased bacterial translocation and anastomosis insufficiency. Thus, it is important to estimate well the optimal distance of the anastomosis line from the last mesenterial vessel. However, it is still empiric. In this experiment the aim was to investigate the intestinal microcirculation at various distances from the anastomosis in a pig model. MATERIALS AND METHODS: On 8 anesthetized pigs paramedian laparotomy and end-to-end jejuno-jejunostomy were performed. Using Cytocam-IDF camera, microcirculatory recordings were taken before surgery at the planned suture line, and 1 to 3 mesenterial vessel mural trunk distance from it, and at the same sites 15 and 120 min after anastomosis completion. After the microcirculation monitoring, anastomosed and intact bowel segments were removed to test tensile strength. RESULTS: The proportion and the density of the perfused vessels decreased significantly after anastomosis completion. The perfusion rate increased gradually distal from the anastomosis, and after 120 min these values seemed to be normalized. Anastomosed bowels had significantly lower maximal tensile strength and higher slope of tensile strength curves than intact controls. CONCLUSION: Alterations in microcirculation and tensile strength were observed. After completing the anastomosis, the improvement in perfusion increased gradually away from the wound edge. The IDF device was useful to monitor intestinal microcirculation providing data to estimate better the optimal distance of the anastomosis from the last order mesenteric vessel.

Local and Systemic Micro-Rheological Changes during Intestinal Anastomosis Operation: A Metabolic Dependence in an Experimental Model.

Hemorheological factors may show arterio-venous differences. Alterations in acid-base and metabolic parameters may also influence these factors. However, little is known about changes in micro-rheological parameters during abdominal surgery, influencing splanchnic circulation. In anesthetized pigs, the external jugular vein, femoral artery and vein were cannulated unilaterally, and paramedian laparotomy was performed. In the anastomosis group, after resecting a bowel segment, end-to-end jejuno-jejunostomy was completed. Blood samples (from cannulas and by puncturing the portal vein) were taken before and after the intervention. Hematological, acid-base and blood gas parameters, metabolites, red blood cell (RBC) deformability and aggregation were determined. The highest hematocrit was found in portal blood, increasing further by the end of operation. A significant pH decrease was seen, and portal blood showed the highest lactate and creatinine concentration. The highest RBC aggregation values were found in arterial, the lowest in renal venous blood. The RBC aggregation increased with higher lactate concentration and lower pH. Osmotic gradient deformability declined, with the lowest values in portal and renal venous samples. In conclusion, micro-rheological parameters showed arterio-venous and porto-renal venous differences, influenced by oxygenation level, pH and lactate concentration. The intestinal anastomosis operation caused an immediate micro-rheological deterioration with portal venous dominancy in this experiment.

A Custom-Tailored Multichannel Pressure Monitoring System Designed for Experimental Surgical Model of Abdominal Compartment Syndrome.

In experimental medicine, a wide variety of sensory measurements are used. One of these is real-time precision pressure measurement. For comparative studies of the complex pathophysiology and surgical management of abdominal compartment syndrome, a multichannel pressure measurement system is essential. An important aspect is that this multichannel pressure measurement system should be able to monitor the pressure conditions in different tissue layers, and compartments, under different settings. We created a 12-channel positive-negative sensor system for simultaneous detection of pressure conditions in the abdominal cavity, the intestines, and the circulatory system. The same pressure sensor was used with different measurement ranges. In this paper, we describe the device and major experiences, advantages, and disadvantages. The sensory systems are capable of real-time, variable frequency sampling and data collection. It is also important to note that the pressure measurement system should be able to measure pressure with high sensitivity, independently of the filling medium (gas, liquid). The multichannel pressure measurement system we developed was well suited for abdominal compartment syndrome experiments and provided data for optimizing the method of negative pressure wound management. The system is also suitable for direct blood pressure measurement, making it appropriate for use in additional experimental surgical models.

Hemorheological and Microcirculatory Relations of Acute Pancreatitis.

Acute pancreatitis still means a serious challenge in clinical practice. Its pathomechanism is complex and has yet to be fully elucidated. Rheological properties of blood play an important role in tissue perfusion and show non-specific changes in acute pancreatitis. An increase in blood and plasma viscosity, impairment of red blood cell deformability, and enhanced red blood cell aggregation caused by metabolic, inflammatory, free radical-related changes and mechanical stress contribute to the deterioration of the blood flow in the large vessels and also in the microcirculation. Revealing the significance of these changes in acute pancreatitis may better explain the pathogenesis and optimize the therapy. In this review, we give an overview of the role of impaired microcirculation by changes in hemorheological properties in acute pancreatitis.

Hematological, Micro-Rheological, and Metabolic Changes Modulated by Local Ischemic Pre- and Post-Conditioning in Rat Limb Ischemia-Reperfusion.

In trauma and orthopedic surgery, limb ischemia-reperfusion (I/R) remains a great challenge. The effect of preventive protocols, including surgical conditioning approaches, is still controversial. We aimed to examine the effects of local ischemic pre-conditioning (PreC) and post-conditioning (PostC) on limb I/R. Anesthetized rats were randomized into sham-operated (control), I/R (120-min limb ischemia with tourniquet), PreC, or PostC groups (3 × 10-min tourniquet ischemia, 10-min reperfusion intervals). Blood samples were taken before and just after the ischemia, and on the first postoperative week for testing hematological, micro-rheological (erythrocyte deformability and aggregation), and metabolic parameters. Histological samples were also taken. Erythrocyte count, hemoglobin, and hematocrit values decreased, while after a temporary decrease, platelet count increased in I/R groups. Erythrocyte deformability impairment and aggregation enhancement were seen after ischemia, more obviously in the PreC group, and less in PostC. Blood pH decreased in all I/R groups. The elevation of creatinine and lactate concentration was the largest in PostC group. Histology did not reveal important differences. In conclusion, limb I/R caused micro-rheological impairment with hematological and metabolic changes. Ischemic pre- and post-conditioning had additive changes in various manners. Post-conditioning showed better micro-rheological effects. However, by these parameters it cannot be decided which protocol is better.

Beneficial postoperative micro-rheological effects of intraoperative administration of diclophenac or ischemic preconditioning in patients with lower extremity operations - Preliminary data.

BACKGROUND: Ischemia-reperfusion (I/R) may worsen blood rheology that has been demonstrated by clinical and experimental data. It is also known that anti-inflammatory agents and preconditioning methods may reduce I/R injury. OBJECTIVE: We aimed to analyze hemorheological alterations in elective knee operations and the effects of intraoperative nonsteroidal anti-inflammatory drug (NSAID) administration and application of ischemic preconditioning. METHODS: Hemorheological variables of 17 patients with total knee replacement or anterior crucial ligament replacement were analyzed. The ischemic (tourniquet) time was 92±15 minutes. Seven patients did not receive NSAID (Control group), 5 patients got i.v. sodium-diclophenac 10 minutes before and 6 hours after reperfusion. Five patients had ischemic preconditioning (3×15 minutes). Blood samples were collected before the ischemia, 10 minutes after reperfusion, on the 1st and 2nd p.o. day. RESULTS: Whole blood viscosity didn't show notable inter-group differences, except for a slight decrease in the preconditioning group. RBC deformability decreased, erythrocyte aggregation enhanced by the 1st and 2nd p.o. days in Control group. In NSAID and preconditioning groups the changes were moderate, aggregation values significantly lowered compared to the Control group. CONCLUSION: Intraoperatively administered diclophenac or ischemic preconditioning could moderate the deterioration in micro-rheological parameters caused by I/R in patients.

Hemorheological and Microcirculatory Factors in Liver Ischemia-Reperfusion Injury-An Update on Pathophysiology, Molecular Mechanisms and Protective Strategies.

Hepatic ischemia-reperfusion injury (IRI) is a multifactorial phenomenon which has been associated with adverse clinical outcomes. IRI related tissue damage is characterized by various chronological events depending on the experimental model or clinical setting. Despite the fact that IRI research has been in the spotlight of scientific interest for over three decades with a significant and continuous increase in publication activity over the years and the large number of pharmacological and surgical therapeutic attempts introduced, not many of these strategies have made their way into everyday clinical practice. Furthermore, the pathomechanism of hepatic IRI has not been fully elucidated yet. In the complex process of the IRI, flow properties of blood are not neglectable. Hemorheological factors play an important role in determining tissue perfusion and orchestrating mechanical shear stress-dependent endothelial functions. Antioxidant and anti-inflammatory agents, ischemic conditioning protocols, dynamic organ preservation techniques may improve rheological properties of the post-reperfusion hepatic blood flow and target endothelial cells, exerting a potent protection against hepatic IRI. In this review paper we give a comprehensive overview of microcirculatory, rheological and molecular-pathophysiological aspects of hepatic circulation in the context of IRI and hepatoprotective approaches.

Impact of groin flap ischemia-reperfusion on red blood cell micro-rheological parameters in a follow-up study on rats.

BACKGROUND: Flap hypoperfusion or ischemia-reperfusion (I/R) may occur during preparation-transposition procedures and by postoperative thrombotic complications. Behind the microcirculatory disturbances micro-rheological alterations are also supposed. OBJECTIVE: We aimed to investigate the groin flap I/R with following-up micro-rheological parameters. METHODS: Anesthetized rats were subjected to Control or I/R groups. Groin flaps were prepared bilaterally, pedicled on the superficial epigastric vessels. In the Control group the flaps were re-sutured after one hour, while in I/R group microvascular clips were applied on the pedicles for 60 minutes, then the flaps were repositioned. Besides daily wound control, before the operation and on the 1st, 3rd, 5th, 7th and 14th postoperative days blood samples were collected for testing red blood cell (RBC) deformability (rotational ektacytometry) and aggregation (light-transmission aggregometry). RESULTS: RBC deformability significantly worsened by the 3rd-7th postoperative day in I/R group. RBC aggregation enhanced significantly by the 1st day, in I/R group it remained elevated on the 3rd day as well. In a complicated case with unilateral flap necrosis, RBC deformability and aggregation worsening was outlined from its group (base, 1st, 3rd day). CONCLUSION: Wound healing affected micro-rheological parameters in the early postoperative period. Flap I/R exacerbated the alterations. The parameters markedly worsened in case of flap necrosis.

Which remote ischemic preconditioning protocol is favorable in renal ischemia-reperfusion injury in the rat?

BACKGROUND: The optimal timing of remote ischemic preconditioning (RIPC) in renal ischemia-reperfusion (I/R) injury is still unclear. We aimed to compare early- and delayed-effect RIPC with hematological, microcirculatory and histomorphological parameters. METHODS: In anesthetized male CrI:WI Control rats (n = 7) laparotomy and femoral artery cannulation were performed. In I/R group (n = 7) additionally a 45-minute unilateral renal ischemia with 120-minute reperfusion was induced. The right hind-limb was strangulated for 3×10 minutes (10-minute intermittent reperfusion) 1 hour (RIPC-1 group, n = 7) or 24 hour (RIPC-24 group, n = 6) prior to the I/R. Hemodynamic, hematological parameters and organs' surface microcirculation were measured. RESULTS: Control and I/R group had the highest heart rate (p < 0.05 vs base), while the lowest mean arterial pressure (p < 0.05 vs RIPC-1) were found in the RIPC-24 group. The highest microcirculation values were measured in the I/R group (liver: p < 0.05 vs Control). The leukocyte count increased in I/R group (base: p < 0.05 vs Control), also this group's histological score was the highest (p < 0.05 vs Control). The RIPC-24 group had a significantly lower score than the RIPC-1 (p = 0.0025 vs RIPC-1). CONCLUSION: Renal I/R caused significant functional and morphological, also in the RIPC groups. According to the histological examination the delayed-effect RIPC method was more effective.

Microrheology, microcirculation and structural compensatory mechanisms of a chronic kidney disease rat model. A preliminary study.

BACKGROUND: Chronic kidney disease (CKD) models are known to study pathophysiology and various treatment methods. Renal dysfunction could influence erythrocytes through several pathways. However, hemorheological and microcirculatory relation of CKD models are not completely studied yet. OBJECTIVE: To evaluate erythrocyte micro-rheology, microcirculatory and structural compensatory mechanisms in a rat model of CKD. METHODS: Female Sprague-Dawley rats were subjected to nephrectomy group (NG, n = 6) or sham-operated group (SG, n = 6). NG rats were subjected to 5/6 nephrectomy in two stages. In SG no intervention was made on kidneys. Hemorheological and hematological measurements were carried out after each stage, and 5 weeks after the last operation. Histological and microcirculatory studies were done on the remaining kidney and compared with sham rats. RESULTS: Serum creatinine increased in NG (p = 0.008), accompanied with decrease of red blood cell count (p = 0.028) and hemoglobin (p = 0.015). Erythrocyte aggregation parameters slightly increased in NG, while the elongation index didn't show significant changes. Microcirculation was intact in the remnant kidney of NG. However, in comparison with SG, the diameter of glomeruli increased significantly (p < 0.01). CONCLUSIONS: Erythrocyte mass was influenced more than micro-rheological properties in this model. The main compensation mechanism was rather structural than at microcirculatory level.

N,N-dimethyltryptamine Prevents Renal Ischemia-Reperfusion Injury in a Rat Model.

BACKGROUND: Ischemia reperfusion (I/R) injury remains one of the most challenging fields of organ transplantation. It is highly associated with the use of expanded criteria donors that might conclude to delayed graft function or early or late graft failure. OBJECTIVE: To investigate the metabolic, microcirculatory parameters, and histologic changes under the effect of N,N-dimethyltryptamine (DMT) in a renal I/R model in rats. METHOD: In 26 anesthetized rats both kidneys were exposed. In the control group (n = 6) no other intervention happened. In 20 other animals, the right renal vessels were ligated, and after 60 minutes the right kidney was removed. The left renal vessels were clamped for 60 minutes then released, followed by 120 minutes of reperfusion. In the I/R group (n = 10), there was no additive treatment, while in I/R + DMT group (n = 10) DMT was administered 15 minutes before ischemia. Blood samples were taken, laser Doppler measurement was performed, and both kidneys were evaluated histologically. RESULTS: Microcirculation (blood flux units [BFU]) diminished in all groups, but remarkably so in the I/R + DMT group. This group compensated better after the 30th minute of reperfusion. The control and I/R + DMT groups had similar BFUs after 120 minutes of reperfusion, but in the I/R group BFU was higher. Tubular necrosis developed in the I/R and I/R + DMT groups too; it was moderated under DMT effect, and severe without. Histologic injuries were less in I/R + DMT Group compared to non-treated animals. CONCLUSION: Histologic changes characteristic to I/R injuries were reversible and microcirculation recovered at the end of 120 minutes reperfusion under the administration of DMT. DMT can be used for renoprotection in kidney transplantation.

Hemodynamic consequences of intravenously given E. coli suspension: observations in a fulminant sepsis model in pigs, a descriptive case-control study.

BACKGROUND: The aim of the present work was to assess systemic hemodynamic changes using PiCCo monitoring in a porcine model of E. coli-induced fulminant sepsis. METHODS: Thirty-one healthy female Hungahib pigs were randomly assigned into control (n = 15) or septic groups (n = 16). In the sepsis group Escherichia coli culture was intravenously administrated in a continuously increasing manner according to the following protocol: 2 ml of bacterial culture suspended in physiological saline was injected in the first 30 min, then 4 ml of bacterial culture was administered within 30 min, followed by infusion of 32 ml bacterial culture for 2 h. Control animals received identical amount of saline infusion. Systemic hemodynamic parameters were assessed by PiCCo monitoring in both groups. RESULTS: Resting hemodynamic parameters were identical in the two groups. In control animals, systemic hemodynamic variables were relatively stable during the entire procedure. In septic animals shock developed in 165 (IQR: 60-255) min after starting the injection of E. coli solution. Blood pressure values gradually decreased, whereas pulse rate increased. A decrease in cardiac index, an increased systemic vascular resistance, and a decreased stroke volume variation were observed. CONCLUSIONS: These results may serve as additional pathophysiological information of hemodynamic changes occurring during hypodynamic sepsis and may contribute to a better understanding of the pathomechanism of septic multiple organ failure.

Renal ischemia-reperfusion-induced metabolic and micro-rheological alterations and their modulation by remote organ ischemic preconditioning protocols in the rat.

BACKGROUND: Pathomechanism and optimal renoprotective protocol for remote ischemic preconditioning (RIPC) have not been completely revealed yet. OBJECTIVE: To investigate micro-rheological effects of early and delayed RIPC in renal ischemia-reperfusion (I/R) in the rat. METHODS: In Control group the left femoral artery was cannulated and the left kidney was gently exposed. In the I/R group 45-minute renal ischemia with 120-minute reperfusion period was monitored. In the RIPC groups a 3×10-minute protocol was applied using tourniquet around the right hind-limb 1 hour (RIPC-1) or 24 hours (RIPC-24) prior to the I/R. Blood samples were taken for testing blood gas, acid-base, metabolic and hemorheological parameters. RESULTS: Lactate and potassium concentration significantly increased in I/R that could be reduced by RIPC, especially in RIPC-24. Creatinine concentration increased further in RIPC groups. I/R and RIPC-1 decreased the pH, RIPC-24 increased. RIPC-24 reduced the drop in base excess. Erythrocyte deformability worsened by renal I/R. In RIPC groups deformability decreased additively. However, RIPC-1 could improve the condition. RIPC-24 showed the highest erythrocyte aggregation values during reperfusion. CONCLUSIONS: Renal I/R worsened metabolic and micro-rheological parameters that could be modulated by RIPC protocols. However, it could not be decided whether the early or the delayed protocol is better.

Is the early or delayed remote ischemic preconditioning the more effective from a microcirculatory and histological point of view in a rat model of partial liver ischemia-reperfusion?1.

PURPOSE: To compare early- and late-effect remote ischemic preconditioning (RIPC) by analysing the microcirculatory, hemodynamic and histological changes in partial liver ischemia-reperfusion of rats. METHODS: 60-minute partial liver ischemia followed by 120-minute reperfusion was performed without (Control group, n=7) or with preconditioning. In RIPC groups a tourniquet was applied around the left thigh using 3 cycles of 10-minute ischemia/10-minute reperfusion, one (RIPC-1, n=7) or twenty-four hours (RIPC-24, n=7) before I/R. Hemodynamic and microcirculatory measurements were performed before and after ischemia and in 30th, 60th and 120th minute of reperfusion and histological examination at the end of reperfusion. RESULTS: Blood pressure decreased in all groups followed by biphasic changes in Control group. In RIPC groups R120 values returned almost to normal. Heart rate increased in Control and RIPC-1 groups at R120, while RIPC-24 did not show significant changes. Microcirculation of non-ischemic liver stayed constant in Control and showed significant changes in RIPC-24 group, while in ischemic liver elevated by R120 in all groups. RIPC didn't reduce histological alterations. CONCLUSION: Considering the survival and the results, both remote ischemic preconditioning protocols had beneficial effect in hepatic ischemia-reperfusion, however the histopathological findings were controversial.

Is the early or delayed remote ischemic preconditioning the more effective from a microcirculatory and histological point of view in a rat model of partial liver ischemia-reperfusion?

Abstract Purpose: To compare early- and late-effect remote ischemic preconditioning (RIPC) by analysing the microcirculatory, hemodynamic and histological changes in partial liver ischemia-reperfusion of rats. Methods: 60-minute partial liver ischemia followed by 120-minute reperfusion was performed without (Control group, n=7) or with preconditioning. In RIPC groups a tourniquet was applied around the left thigh using 3 cycles of 10-minute ischemia/10-minute reperfusion, one (RIPC-1, n=7) or twenty-four hours (RIPC-24, n=7) before I/R. Hemodynamic and microcirculatory measurements were performed before and after ischemia and in 30th, 60th and 120th minute of reperfusion and histological examination at the end of reperfusion. Results: Blood pressure decreased in all groups followed by biphasic changes in Control group. In RIPC groups R120 values returned almost to normal. Heart rate increased in Control and RIPC-1 groups at R120, while RIPC-24 did not show significant changes. Microcirculation of non-ischemic liver stayed constant in Control and showed significant changes in RIPC-24 group, while in ischemic liver elevated by R120 in all groups. RIPC didn't reduce histological alterations. Conclusion: Considering the survival and the results, both remote ischemic preconditioning protocols had beneficial effect in hepatic ischemia-reperfusion, however the histopathological findings were controversial.

Beneficial effects of remote organ ischemic preconditioning on micro-rheological parameters during liver ischemia-reperfusion in the rat.

BACKGROUND: Remote ischemic preconditioning (RIPC) can be protective against the damage. However, there is no consensus on the optimal amount of tissue, the number and duration of the ischemic cycles, and the timing of the preconditioning. The hemorheological background of the process is also unknown. OBJECTIVE: To investigate the effects of remote organ ischemic preconditioning on micro-rheological parameters during liver ischemia-reperfusion in rats. METHODS: In anesthetized rats 60-minute partial liver ischemia was induced with 120-minute reperfusion (Control, n = 7). In the preconditioned groups a tourniquet was applied on the left thigh for 3×10 minutes 1 hour (RIPC-1, n = 7) or 24 hours (RIPC-24, n = 7) prior to the liver ischemia. Blood samples were taken before the operation and during the reperfusion. Acid-base, hematological parameters, erythrocyte aggregation and deformability were tested. RESULTS: Lactate concentration significantly increased by the end of the reperfusion. Erythrocyte deformability was improved in the RIPC-1 group, erythrocyte aggregation increased during the reperfusion, particularly in the RIPC-24 group. CONCLUSIONS: RIPC alleviated several hemorheological changes caused by the liver I/R. However, the optimal timing of the RIPC cannot be defined based on these results.

Effects and influencing factors on hemorheological variables taken into consideration in surgical pathophysiology research.

In surgical pathophysiology ischemia-reperfusion, inflammatory processes, sepsis, vascular interventions, tissue trauma, shock, all mean conditions in which hemorheological parameters show alterations. Despite of numerous clinical and experimental studies, the in vivo hemorheology is not completely understood yet, and several fundamental questions still need to be answered. Investigating these issues, experimental surgical models are important, in point of view of the translational research as well. In this paper we aimed to make an attempt on summarizing the possible factors and conditions that might have an effect on hemorheological results in experimental surgical studies. Hemorheological parameters show alterations in surgical pathophysiological processes in a complex way. However, the changes are dominantly non-specific. Standardized experimental conditions, related to the experimental animal (species, animal welfare) anesthesia-medications, operation, sampling and, if applicable, conditions of the postoperative period, are inevitable for a safe assessment of valuable (hemorheological) results. Parallel investigations - such as microcirculatory monitoring, imaging techniques, other laboratory methods, histomorphology- have great importance, together with individual analysis of changes, for a better understanding of the changes and for comparability with clinical results.

Age- and gender-related hemorheological alterations in intestinal ischemia-reperfusion in the rat.

BACKGROUND: Intestinal ischemia-reperfusion (I/R) is a life-threatening clinical disorder. During I/R, the microrheological parameters of blood (red blood cell deformability and aggregation) worsen, which may contribute to microcirculatory deterioration. Age and gender also have a great influence on hemorheological parameters. We aimed to investigate the gender and age-related microrheological alterations during intestinal I/R. MATERIALS AND METHODS: After the cannulation of the left femoral artery, median laparotomy was performed in Crl:WI rats under general anesthesia. In the young control animals there were no other interventions (female n = 7; male n = 7). In the young (female n = 7; male n = 7) and older I/R groups (female n = 6; male n = 6), the superior mesenteric artery was clipped for 30 min, and a 120-min reperfusion period was observed afterward. Blood samples were taken before and at the 30-min ischemia, in the 30th, 60th, and 120th min of the reperfusion. Hematological parameters, erythrocyte deformability, and aggregation were determined. RESULTS: Hematocrit increased significantly in the younger female I/R group. Red blood cell count was higher in male and older animals. In case of white blood cell count, male animals had higher values compared with females. Platelet count elevated in the younger male and older female I/R animals. Red blood cell deformability worsened, mainly in the male and older I/R groups. Enhanced erythrocyte aggregation was seen in all groups, being more expressed in the female I/R groups. CONCLUSIONS: Microrheological parameters show gender and age-related differences during intestinal I/R. These observations have importance in the planning and evaluation of experimental data.

Hemorheological and metabolic consequences of renal ischemia-reperfusion and their modulation by N,N-dimethyl-tryptamine on a rat model.

BACKGROUND: Micro-rheological relations of renal ischemia-reperfusion (I/R) have not been completely elucidated yet. Concerning anti-inflammatory agents, it is supposed that sigma-1 receptor agonist N,N-dimethyl-tryptamin (DMT) can be useful to reduce I/R injury. OBJECTIVE: To investigate the micro-rheological and metabolic parameters, and the effects of DMT in renal I/R in rats. METHODS: In anesthetized rats from median laparotomy both kidneys were exposed. In Control group (n = 6) no other intervention happened. In I/R group (n = 10) the right renal vessels were ligated and after 60 minutes the organ was removed. The left renal vessels were clamped for 60 minutes followed by 120-minute reperfusion. In I/R+DMT group (n = 10) DMT was administered 15 minutes before the ischemia. Blood samples were taken before/after ischemia and during the reperfusion for testing hematological, metabolic parameters, erythrocyte deformability and aggregation. RESULTS: Lactate concentration significantly increased and accompanied with decreased blood pH. Enhanced erythrocyte aggregation and impaired deformability were observed from the 30th minute of reperfusion. In I/R+DMT group we found diminished changes compared to the I/R group (lactate, pH, electrolytes, red blood cell deformability and aggregation). CONCLUSIONS: Metabolic and micro-rheological parameters impair during renal I/R. DMT could reduce but not completely prevent the changes in this rat model.

Effects of aging and gender on micro-rheology of blood in 3 to 18 months old male and female Wistar (Crl:WI) rats.

BACKGROUND: Age- and gender-related alterations of hemorheological parameters have not been completely elucidated to date. Experiments on older animals may give valuable information on this issue. However, the majority of rheological studies have been performed in young rodents. OBJECTIVE: We aimed to investigate the influence of aging and gender on hemorheological parameters in rats. METHODS: Coeval male (n=10) and female (n=10) Wistar (Crl:WI) rats were followed-up over 15 months. Blood samples were obtained from the lateral tail vein at 3, 4, 5, 9, 12, 15 and 18 months of age. Hematological parameters, red blood cell deformability (elongation under shear), osmotic gradient deformability and erythrocyte aggregation were tested. Body weight and the estrus cycle (in females) were also examined. RESULTS: Erythrocyte aggregation showed age- and gender-related variations. Red blood cell deformability was greater in females and gradually decreased over the 15-month period in both genders. Erythrocyte aggregation was greater in male rats at most ages, but did not show consistent changes with age. CONCLUSIONS: The micro-rheological parameters showed age-related alterations with gender differences. The effect of the estrous cycle cannot be excluded in female rats. The results provide reference data for studies of aging in rats and of the mechanism related to age and gender differences in hemorheology.