Bosentan normalizes the GFR response to renal nerve stimulation following reversible unilateral ureteric obstruction in the rat

We investigated the renal response to direct renal nerve stimulation, 2 weeks following reversal of 24-h unilateral (left) ureteric obstruction. Renal nerve stimulation caused a 13-15 % fall in renal blood flow, in 4 groups of anesthetized rats following ureteric obstruction (n=9) or a sham operation (n=7) both with (n=9) and without (n=7) treatment with the mixed ET(A/B) receptor antagonist, bosentan. In the sham-operated rats, renal nerve stimulation did not change glomerular filtration rate but reduced urine flow rate (37+/-3 %, P<0.001), and absolute (38+/-4 %, P<0.001) and fractional (35+/-5 %, P<0.01) sodium excretion. Following unilateral ureteric obstruction, renal nerve stimulation increased glomerular filtration rate by 22+/-3 % (P<0.01), but reduced urine flow rate (14+/-2 %, P<0.001) and fractional sodium excretion (23+/-5 %, P<0.01). Bosentan treatment had no effect on baseline or renal responses to renal nerve stimulation in the sham group but normalized the renal response to renal nerve stimulation in the unilateral ureteric obstruction group. We conclude that 14 days after a 24-h period of unilateral ureteric obstruction there is an increase in GFR in response to direct renal nerve stimulation, which is due, in part, to the actions of endothelin at the time of obstruction.

betaA- and betaC-activin, follistatin, activin receptor mRNA and betaC-activin peptide expression during rat liver regeneration

The mRNA expression of two activin growth factor subunits (betaA- and betaC-activin), activin receptor subunits (ActRIIA, ActRIIB) and the activin-binding protein follistatin, and peptide expression of betaA-activin and betaC-activin subunits, were examined in regenerating rat liver after partial hepatectomy (PHx). Liver samples were collected from adult, male Sprague-Dawley rats, 12-240 h (n=3-5 rats per time point) after PHx or from sham-operated controls at the same time points. Hepatocyte mitosis and apoptosis were assessed histologically and by in situ cell death detection. RT and PCR were used to assess relative gene expression. betaA- and betaC-activin peptide immunoreactivity was assessed in liver and serum samples by western blotting, whereas cellular expression was investigated by immunohistochemistry, using specific monoclonal antibodies. betaA- and betaC-activin mRNA dropped to < 50% of sham control values 12 h after PHx and remained at this level until 168 h post-PHx, when betaA-activin expression increased to three times sham control values and betaC-activin mRNA returned to pre-PHx levels. A peak in follistatin expression was observed 24-48 h post-PHx, coincident with an increase in hepatocyte mitosis. No changes were observed in ActRIIA mRNA, whereas ActRIIB expression paralleled that of betaA-activin mRNA. betaC-activin immunoreactive homo- and heterodimers were observed in regenerating liver and serum. Mitotic hepatocytes frequently contained betaC-activin immunoreactivity, whereas apoptotic hepatocytes were often immunoreactive for betaA-activin. We conclude that betaA- and betaC-activin subunit proteins are autocrine growth regulators in regenerating liver and when expressed independently lead to hepatocyte apoptosis or mitosis in a subset of hepatocytes.

Effect of ischemia-reperfusion injury on the microcirculation of the steatotic liver of the Zucker rat

BACKGROUND

Much discussion has been focused on the use of steatotic livers for transplantation due to the prevalence of steatosis in the potential donor liver pool (1). The aim of this study was to investigate the possibility that the microcirculation of steatotic liver is more sensitive to the ischemia-reperfusion (IR) injury than normal liver.

METHODS

The left liver lobe of obese (n=9) and lean Zucker rats (n=9) were subjected to 40 min of warm ischemia followed by 60 min of reperfusion. Fluorescent probes rhodamine 123 (Rh123), bisbenzimide (Bis), and rhodamine 6G (Rh6G) were administered for the identification by intravital fluorescence microscopy (IVFM) of mitochondrial membrane potential, hepatocyte nuclei and leukocytes, respectively before hepatic ischemia and at 15, 30, 45, and 60 min after reperfusion. Blood samples were obtained before and after 60 min of reperfusion. Liver tissue was taken at the end of experiment for histological analysis.

RESULTS

The liver of the obese rats showed prominent macro- and microvesicular fatty changes (MAFC and MIFC) and hepatocyte swelling. Under IVFM, the obese animals had significantly wider hepatic cords (23.1+/-0.8 microm) than the lean ones (15.9+/-0.5 microm) (P<0.01), whereas no significant difference in sinusoidal diameters was noted. The number of functional sinusoids significantly decreased after 30 min of reperfusion in both groups but no significant change was noted in the nucleus count throughout the experiment. Rh123 fluorescence intensity dropped significantly in the obese group after 60 min of reperfusion but not in the lean rats. Leukocyte adherence showed a significant rise after reperfusion in both groups. Plasma AST and ALT levels were 40- and 24-fold higher respectively for the obese animals after IR compared with their preischemic values, whereas the corresponding increase were 4.2- and 3.4-fold for the lean animals, respectively.

CONCLUSIONS

Our results indicate that the liver of the obese Zucker rat is steatotic and presents with an abnormal microcirculation manifested by a reduced sinusoidal density. IR led to significantly greater hepatic injury in the steatotic than in the normal liver. This injury was accompanied by a significant reduction in the functional sinusoidal density and mitochondrial membrane potential as assessed by Rh123-associated fluorescence in the steatotic liver. In conclusion, the increased sensitivity of the steatotic liver to IR injury would appear to involve both alterations in blood flow in the microcirculation and to cellular changes.

Microvascular origin of laser-Doppler flux signal from the surface of normal and injured liver of the rat

Although laser-Doppler flowmetry (LDF) is a widely used technique, little is known about its microvascular origin from the surface of the liver. In the present study, we attempted to identify the microvascular bed interrogated by the laser light, by correlating perfusion and red blood cell velocity data obtained using intravital fluorescence microscopy (IVFM) with the LDF signal recorded under normal conditions and following liver injury. Sprague-Dawley rats which underwent hepatic artery ligation (HAL) or nonarterialized liver transplantation (NOLT) served as in vivo models of reduced sinusoidal red blood cell velocity (RBC(vel)) and altered homogeneity of perfusion, respectively. Three groups of animals were studied: HAL (n = 8), NOLT (n = 8), and sham-operated control (n = 8). Homogeneous perfusion of the sinusoids and liver lobules and reduced sinusoidal RBC(vel) were initially confirmed in the HAL group. In addition, significantly reduced sinusoidal and lobular perfusion was observed in the NOLT liver. HAL caused a 28% reduction in the LDF signal (P < 0.05 vs sham), whereas the LDF signal from the NOLT liver (101 +/- 11 PU) was lower than that from the native recipient liver with HAL (128 +/- 11 PU). Under control conditions, and following HAL and NOLT, a linear correlation could be established only between sinusoidal RBC(vel) and LDF signal (y = 0.78x + 50.98, r2 = 0.71, P < 0.001). Furthermore, using IVFM images and NIH Image analysis, we estimated a high contribution of the sinusoids to the total vascular space at the liver periphery. Our data indicate that under normal conditions and those of altered microcirculation, blood flow in the sinusoids, compared to other microvessels, has a significant influence on the LDF signal from the surface of the liver.

The role of endothelin in early renal cortical reperfusionin renal transplantation

The role of specific endothelin receptors in the early renal reperfusion and long-term survival in renal transplantation was investigated in Lewis rats. Left renal transplantation was performed following 2 h cold ischaemia without and with ET(A) receptor antagonism and following 16 h cold ischaemia with no treatment, with ET(A) receptor antagonism and with ET(B) receptor antagonism. The ET(A) and ET(B) receptor antagonists, BQ-610 and A-192621 respectively, were added to the preservation solution. Renal cortical perfusion (RCP) was measured postoperatively using laser Doppler flowmetry. All rats in the 2-hour groups survived for 15 days. Animals in the untreated 16-hour group or in the A-192621-treated group died between days 3 and 6 after surgery. Fifty percent of the rats in the 16-hour and BQ-610-treated group died between days 4 and 7 after surgery while the other 50% survived for 15 days. Survival rates correlated well with both the postoperative serum creatinine and the recovery of RCP. We conclude that addition of an ET(A) receptor antagonist to the preservation solution improves renal reperfusion and long-term survival following prolonged ischaemia, whereas ET(B) receptor antagonism does neither.

Role of endothelin ET(A) receptor antagonism in the post-transplant renal response to angiotensin II in the rat

The role of endothelins in the renal damage associated with ischaemic-reperfusion (I-R) injury during organ transplantation was determined by selective blockade of the ET(A) receptors with the receptor antagonist ABT-627. The integrity of kidney function was determined 2 and 8 weeks after transplantation by investigation of the renal response to angiotensin II. Under pentobarbitone anaesthesia (70 mg x kg(-1), I.P.), rats underwent a right nephrectomy. Transplantation of the left kidney was performed after 2 h cold ischaemia without or with ABT-627 treatment. Control animals underwent left renal denervation. The renal response to angiotensin II was measured 2 weeks later following blockade of endogenous production of angiotensin II with captopril. A further transplant group was allowed to recover for 8 weeks before the terminal study. In the control group, angiotensin II reduced renal blood flow (RBF), glomerular filtration rate (GFR), urine flow rate (UV), and fractional sodium excretion (FE(Na)) by 29 +/- 5 %, 19 +/- 4 %, 25 +/- 4 % and 32 +/- 7 %, respectively. Conversely, in the transplant group, angiotensin II left RBF unchanged and increased GFR (59 +/- 12 %) and UV (93 +/- 8 %). FE(Na) decreased by 24 +/- 9 %. In both the transplant group treated with ABT-627 and the long-term recovery group, the renal response to angiotensin II was normalised. In conclusion, renal transplantation following 2 h cold I-R injury resulted in a temporary abnormal renal response to angiotensin II, which was reversed by ET(A) receptor antagonism at the time of transplantation.

Endotelin ETA and ETB receptor antagonism during cold preservation in renal transplantation

BACKGROUND

In this study, we investigated the effects of selective endothelin (ET) receptor antagonism during different periods of cold ischemia on glomerular and tubular function and long-term survival in renal transplantation.

METHODS

Left renal transplantation was performed in Lewis rats after 2 hr of cold ischemia without (n=8) and with (n=6) ETA receptor antagonism and after 16 hr of cold ischemia without treatment (n=6), with ETA receptor antagonism (n=8) and with ETB receptor antagonism (n=6). A control group (n=8) underwent right nephrectomy and left renal denervation. The ETA and ETB receptor antagonists (BQ-610 and A-192621, respectively) were added to the preservation solution (EuroCollins). After transplantation, renal glomerular and tubular functions were monitored for up to 60 days or death.

RESULTS

All animals in the control and 2-hr groups survived the follow-up protocol, with early postoperative recovery of glomerular and tubular function while the entire untreated 16-hr group died between day 3-6 postoperatively. BQ-610 treatment had no measurable effect on the renal function in the 2-hr group, however, it improved glomerular and tubular functions and led to 50% long-term survival (60 days) in the 16-hr group. A-192621 treatment had no effect on long-term survival or renal parameters.

CONCLUSION

ETA receptor antagonism had protective renal effects after prolonged ischemic preservation in renal transplantation while ETB receptor antagonism had not.

Intra- and post-operative assessment of renal cortical perfusion by laser Doppler flowmetry in renal transplantation in the rat

Renal blood flow (RBF) in the period immediately following transplantation has an important prognostic value. Here we report for the first time on the use of laser Doppler flowmetry (LDF) for the measurement of renal cortical perfusion (RCP) during all the important steps in renal transplantation. Left orthotopic kidney transplantation was performed in Lewis rats (n = 14) after 2 h of cold ischaemia and preservation in EuroCollins solution. Under baseline conditions, RCP in the donor and recipient kidneys were similar with a coefficient of variability of 11 and 12%, respectively. There was a progressive increase in RCP during the first 60 min after transplantation with a return to normal values 2 weeks later. In conclusion, LDF provides a rapid and continuous measure of RCP without interference to the operative site and may prove a useful tool for the measurement of RBF during kidney transplantation.

A novel approach to the quantification of hepatic stellate cells in intravital fluorescence microscopy of the liver using a computerized image analysis system

Hepatic stellate cells (HSC) are nonparenchymal liver cells which reside in the space of Disse within the hepatic microcirculatory unit. HSC can be distinguished using intravital fluorescent microscopy (IVFM) due to the autofluorescence from their intracellular vitamin A. Herein we report on a novel approach for the quantification of video-recorded rat HSC images acquired by IVFM (excitation 360 nm/emission 420 nm) by the combined use of the "Cell counting macro" and the "Measurement macros" in the NIH image software. The approach involved two major steps using (i) the "Cell counting macro" for automatic detection, threshold-setting, and generation of a binary image of the vitamin A autofluorescence in the HSC images and (ii) the "Compute percent black and white" command in the "Measurement macros" to automatically determine the HSC density (%), which was then expressed as percentage of the total area of vitamin A autofluorescence-associated sites per observation area. Comparing the vitamin A autofluorescence areas in the original and the binary fashion HSC images revealed that the "Cell counting macro" was an optimal option for the analysis of the low-magnification (x10 objective) HSC images, whereas this macro was not suitable for the analysis of the higher magnification (40x objective) HSC images unless modifications were made. Our analysis revealed that HSC represent approximately 4-5% of the total area of the liver surface. In analyzing the higher magnification HSC microfluorographs, the use of the original "Cell counting macro" resulted in a significant underestimation of HSC density (60% reduction, P < 0.01) when compared with those analyzed using our modified macro. This study represents the first report of an automatic and reliable approach to the intravital fluorescent microscopic quantification of HSC using a computer-NIH image analysis system.

Dynamic study of the distribution of microcirculatory blood flow in multiple splanchnic organs in septic shock

OBJECTIVES

To study dynamic distribution of microcirculatory blood flow in multiple splanchnic organs during septic shock; to test the hypothesis that changes in microcirculatory blood flow in splanchnic organs correlate with changes in regional flow during septic shock.

DESIGN

A prospective, controlled, animal study.

SETTING

Animal laboratory in a university medical center.

SUBJECTS

Nine anesthetized and mechanically ventilated domestic pigs.

INTERVENTIONS

Systemic flow (cardiac output) was measured with thermodilution and regional (superior mesenteric artery) flow with transit time flowmetry. Local blood flow (microcirculatory flow) was continuously measured in splanchnic organs (gastric, jejunal, and colon mucosa, liver, and pancreas) and the kidney with multichannel laser Doppler flowmetry. Septic shock was induced with fecal peritonitis. After 240 mins of sepsis, intravenous fluids were administered to alter hypodynamic shock to hyperdynamic septic shock.

MEASUREMENTS AND MAIN RESULTS

In this severe septic shock model, systemic and regional flows decreased by approximately 50% during the first 240 mins. Similar reductions were recorded in microcirculatory flow in the mucosa of the stomach (-41%; p < .001) and colon (-47%; p < .001). In the jejunal mucosa, on the other hand, flow remained virtually unchanged. Microcirculatory flow was also significantly decreased in the liver (-49%; p < .001), pancreas (-56%; p < .001), and kidney (-44%; p < .001). Administration of intravenous fluids at 240 mins was followed by three-fold increases in systemic and regional flows (approximately 70% above baseline). In the jejunal mucosa, flow also increased significantly above baseline (42%; p < .001), whereas in the stomach and the colon, it barely reached baseline. Kidney blood flow increased to baseline, whereas pancreas and liver flows remained 26% (p < .05) and 34% (p < .001), respectively, below baseline.

CONCLUSION

Changes in microcirculatory blood flow in the splanchnic organs are heterogeneous, both in early hypodynamic and in hyperdynamic septic shock, and cannot be predicted from changes in systemic or regional flows. Microcirculatory blood flow in the jejunal mucosa remains constant during early septic shock, whereas pancreatic blood flow decreases significantly more than regional flow.

Long-term renal effects of unilateral ureteral obstruction and the role of endothelin

BACKGROUND

Angiotensin II (Ang II) and endothelin (ET) are involved in the alteration of renal function in unilateral ureteral obstruction (UUO). The renal response to Ang II following the reversal of a 24-hour UUO and the effect of ET blockade by bosentan during the time of obstruction were investigated.

METHODS

Following blockade of the endogenous production of Ang II by captopril, the renal response to Ang II was studied in rats 15 to 18 days after a 24-hour UUO (N = 10) or a sham operation (N = 9) both with (N = 10) and without (N = 8) bosentan treatment in the periobstruction period. Similar studies were performed in another group (N = 9) two months following the reversal of obstruction.

RESULTS

In the sham-operated group, Ang II reduced renal blood flow (RBF) by 42 +/- 9% (P < 0.01), glomerular filtration rate (GFR) by 30 +/- 8% (P < 0.01), urine volume (UV) by 44 +/- 9% (P < 0.001), and absolute (UNaV) and fractional sodium excretion (FENa) by 52 +/- 9% (P < 0.001) and 33 +/- 9% (P = 0.054), respectively. In the previously obstructed kidney, Ang II did not change RBF but increased GFR by 106 +/- 40% (P < 0.01), UV by 75 +/- 21% (P < 0.001), UNaV by 190 +/- 60% (P < 0.001), and FENa by 40 +/- 13% (P < 0.05). Bosentan treatment in the obstructed group prevented these Ang II-induced effects and did not have any effect on the sham-operated kidney. Two months following reversal of the obstruction, the response of the kidney was similar to that of the control kidney.

CONCLUSION

Twenty-four-hour UUO results in a temporary abnormality in the renal response to Ang II, which is due, in part, to the actions of ET at the time of obstruction.

Application of a new sleeve anastomosis technique to graft rearterialization in rat liver transplantation

A new rearterialized orthotopic liver transplant (OLT) model in the rat is described. The model involved performing a novel sleeve anastomosis technique for graft rearterialization which consisted of three extraluminal suture anastomoses between the recipient's proper and the donor's common hepatic artery. The total surgical time and in particular the time required to perform the arterial anastomosis was significantly reduced with the utilization of this technique. Hepatic artery patency was 100% and the 4-week survival rate was greater than 90%. Applying this novel sleeve anastomosis technique not only simplifies the rearterialized rat OLT but also ensures that blood flow to all vascular beds is undisturbed.

Continuous measurements of microcirculatory blood flow in gastrointestinal organs during acute haemorrhage

Hypoperfusion of splanchnic organs is an important contributor to the development of multiple organ failure after major surgery and trauma. During general anaesthesia and surgery we compared changes in systemic haemodynamics and regional blood flow with changes in the distribution of microcirculatory flow (MBF) in multiple splanchnic organs in pigs exposed to acute haemorrhage. Seven pigs (25 kg) were bled to a mean arterial pressure of 40 mm Hg; 180 min later the shed blood was retransfused. MBF was measured in the intestinal mucosa (stomach, jejunum, colon), pancreas, liver and kidney using a six-channel laser Doppler flowmeter. Cardiac output was measured by thermodilution and superior mesenteric artery flow by ultrasonic flowmetry. During haemorrhage, MBF in the gastric and colon mucosa and flow in the liver and kidney decreased to a similar extent to regional and systemic flows (30-50%). In contrast, MBF in the jejunal mucosa remained virtually unchanged and flow in the pancreas decreased significantly more than systemic and regional flows (60%, P < 0.05). We conclude that: (1) changes in the distribution of MBF in the gastrointestinal tract during acute haemorrhage are heterogeneous and cannot be predicted from changes in systemic or regional haemodynamics; (2) MBF in the jejunal mucosa did not decrease during haemorrhage, indicating that autoregulation of blood flow in the mucosa remained intact during shock; and (3) MBF in the pancreas decreased significantly more than systemic and regional flows during shock, suggesting that the pancreas is particularly vulnerable to haemorrhage.

Successful hepatic grafting after partial portal vein ligation in the rat: complete reversal of hemodynamic abnormalities

BACKGROUND

Partial portal vein ligation (PPVL) is an established approach in the study of prehepatic portal hypertension in animals. The effect of orthotopic liver transplants (OLT) on hemodynamics in PPVL animals has not been investigated to date. The aim of this study was to develop a model of OLT in PPVL rats and to investigate its hemodynamic consequences.

METHODS

Three groups of male Lewis rats were investigated (1) control animals (n=7), (2) PPVL (n=9), and (3) PPVL/OLT (n=16). Three weeks after PPVL, 9 animals were taken for hemodynamic measurements. OLT was performed in the remaining 16 PPVL rats (PPVL/OLT), and, 4 weeks later, hemodynamic measurements were made. Blood biochemical analysis was performed at different time points in all 3 groups.

RESULTS

The PPVL animals presented with hyperdynamic systemic circulation, extensive collateral vascularization in the hilar region, and portal-systemic shunting (portal systemic shunting; 35.3+/-5.5%). In the PPVL/OLT group, 15 rats survived for 4 weeks (survival: 93.8%, 15 of 16). Of these PPVL/OLT rats, 3 died during the blood sampling protocol. In 3 PPVL/OLT rats, abnormal liver function and histology were found and deranged systemic and hepatic hemodynamics persisted after OLT. In the remaining 9 PPVL/OLT rats, systemic and hepatic hemodynamics had returned to normal at 4 weeks and portal systemic shunting was markedly reduced (2.5+/-0.9%). Liver function was in the normal range.

CONCLUSIONS

(1) The possibility of performing OLT in PPVL rats with a high rate of survival has been confirmed. (2) In the majority of cases, complete reversal of hemodynamic abnormalities in the PPVL animals occurs after OLT (3). PPVL/OLT represents a new and important model in OLT research.

Regular slow wave flowmotion in skeletal muscle is not determined by nitric oxide and endothelin

In a previous study we showed that the generation of regular slow wave flowmotion (rSWFM, 1-3 cycles per minute) in skeletal muscle of anesthetized rats was related to local changes of arterial pressure and microcirculatory blood flow (MBF), which suggests an involvement of pressure- or flow-induced mechanisms. The present experiments were designed to test the role of flow-dependent endothelial autacoids, such as nitric oxide (NO) and endothelin, in the generation of SWFM. The effects of NO-donor sodium nitroprusside (SNP), the partly NO-dependent metabolite adenosine (ADO), the NO-synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME), and the mixed endothelin receptor blocker bosentan (BOS) were analyzed. MBF and rSWFM were assessed by laser Doppler flowmetry. rSWFM appeared in 7 out of 14 preparations after ADO (200 microg/kg/min), but not after SNP (100 microg/kg/min), L-NAME (30 mg/kg iv), and BOS (10 mg/kg iv). Its occurrence was associated with a significant decrease in arterial pressure to 50 +/- 3% (mean +/- SEM) of the baseline, provided that MBF was not enhanced. When given after induction of rSWFM by a 25% hemorrhage, SNP (50 microg/kg/min) totally abolished rSWFM and ADO (100 microg/kg/min) reduced rSWFM frequency from 2.17 +/- 0.08 to 1.72 +/- 0.08 cycles per minute (cpm) (P < 0.05), whereas the frequency was not affected by the other drugs. ADO, l-NAME (30 mg/kg iv), and BOS (10 mg/kg iv) lead to changes in rSWFM amplitude which showed a drug-independent negative correlation to changes in both MAP and MBF (R(2) = 0.61, multiple regression) in the ranges of 57-176% of MAP before drug application, and 72-120% of MBF, respectively. We conclude that NO and endothelin are not involved in the generation of rSWFM. Our findings strongly suggest that the activity of rSWFM depends on a reduction of vascular wall tension and is inhibited by SNP.

Effects of sodium nitroprusside and phenylephrine on blood flow in free musculocutaneous flaps during general anesthesia

BACKGROUND

Hypoperfusion and necrosis in free flaps used to correct tissue defects remain important clinical problems. The authors studied the effects of two vasoactive drugs, sodium nitroprusside and phenylephrine, which are used frequently in anesthetic practice, on total blood flow and microcirculatory flow in free musculocutaneous flaps during general anesthesia.

METHODS

In a porcine model (n = 9) in which clinical conditions for anesthesia and microvascular surgery were simulated, latissimus dorsi free flaps were transferred to the lower extremity. Total blood flow in the flaps was measured using ultrasound flowmetry and microcirculatory flow was measured using laser Doppler flowmetry. The effects of sodium nitroprusside and phenylephrine were studied during local infusion through the feeding artery of the flap and during systemic administration.

RESULTS

Systemic sodium nitroprusside caused a 30% decrease in mean arterial pressure, but cardiac output did not change. The total flow in the flap decreased by 40% (P < 0.01), and microcirculatory flow decreased by 23% in the skin (P < 0.01) and by 30% in the muscle (P < 0.01) of the flap. Sodium nitroprusside infused locally into the flap artery increased the total flap flow by 20% (P < 0.01). Systemic phenylephrine caused a 30% increase in mean arterial pressure, whereas heart rate, cardiac output, and flap blood flow did not change. Local phenylephrine caused a 30% decrease (P < 0.01) in the total flap flow.

CONCLUSIONS

Systemic phenylephrine in a dose increasing the systemic vascular resistance and arterial pressure by 30% appears to have no adverse effects on blood flow in free musculocutaneous flaps. Sodium nitroprusside, however, in a dose causing a 30% decrease in systemic vascular resistance and arterial pressure, causes a severe reduction in free flap blood flow despite maintaining cardiac output.

Dissociation between volume blood flow and laser-Doppler signal from rat muscle during changes in vascular tone

Although the laser-Doppler flowmetry (LDF) signal from skeletal muscle has been shown to provide a good measure of blood flow under some conditions, its behavior during administration of vasoactive substances has never been addressed. The aims of this study were to compare 1) changes in LDF signal with those in total muscle blood flow measured with radioactive microspheres after ganglionic blockade (chlorisondamine) and during administration of angiotensin II (ANG II), phenylephrine (PE), and isoproterenol (Iso) and 2) changes in vascular resistance estimated by the two techniques. The LDF signal from the biceps femoris muscle was investigated in anesthetized male Wistar rats. Ganglionic blockade led to a significant (P < 0.05) fall in mean arterial pressure (MAP) [medians (lower, upper quartiles): 78 (72, 83) vs. 127 (114, 138) mmHg under basal conditions], muscle blood flow (MBF, microsphere technique; 61%), and the LDF signal (29%). Muscle vascular resistance (MVR = MAP/MBF) was increased (64%, P < 0.05), but vascular resistance estimated as MAP/LDF signal (MVRLDF) was unchanged. During ANG II and PE infusions, MAP rose (P < 0.05) to 178 (155, 194) and 127 (124, 142) mmHg, respectively; MBF did not change compared with the preinfusion (postganglionic blockade) level and remained significantly (P < 0.05) lower than baseline, whereas the LDF signal increased up to a level not different from baseline. MVR rose and was significantly (P < 0.05) higher than baseline, whereas MVRLDF did not differ significantly from baseline. During Iso infusion, MAP fell [58 (56, 60) vs. 94 (92, 102) mmHg, P < 0.05], the LDF signal was reduced (49%, P < 0.05) despite a large increase in MBF (139%, P < 0.05), and MVR fell (74%, P < 0.05), whereas MVRLDF did not change vs. preinfusion level. Our results suggest that 1) changes in the LDF signal from muscle may not correlate with changes in total muscle blood flow measured by the microsphere technique during infusion of vasoactive substances and 2) the use of LDF data for estimation of MVR during changes in vascular tone in rat skeletal muscle is probably not appropriate.

Evaluation of laser Doppler flowmetry to assess cyclosporine A-induced impairment of renal blood flow

Cyclosporine A (CyA)-induced nephrotoxicity is a well-known complication of this potent immunosuppressive drug. It is caused by an elevation in renovascular resistance and impairment of renal blood flow. Currently, one of the principal experimental settings to assess renal hemodynamics has been using the in vivo fluorescent videomicroscopy (IVFV) method on hydronephrotic rat kidneys, which is expensive, time-consuming, not physiological, and not applicable to humans. In the present paper we have been able to confirm our working hypothesis that laser Doppler flowmetry (LDF) is a valuable tool for assessing microcirculatory changes in the rat kidney during CyA administration. Total subcapsular blood flow decreased to approximately 70% of baseline values (P < 0.05) and mean arterial pressure (MAP) increased initially to 113% of baseline values (P < 0.05) compared to only minor changes for cremophor (carrier substance) or no changes for sodium chloride solution 0.9%. LDF provides an easy and rapid technique and its major advantage is the potential use in assessing microcirculatory changes after kidney transplants in humans.

Measurement of blood perfusion in the dental pulp with laser Doppler flowmetry

The reproducibility of laser Doppler flowmetry (LDF) in measuring the perfusion of the dental pulp was investigated. A second aim was to establish if the LDF signal from the dental pulp can be influenced by physiological stimuli, e.g. postural changes. A third aim was to apply the technique to clinical measurements of pulp perfusion in patients undergoing orthodontic therapy. A custom splint to position the probe was fabricated for 10 subjects, and measurements of pulpal perfusion in the maxillary six anterior teeth were repeated on eight occasions with the subject seated. Further, measurements of the dental pulp perfusion in one tooth were repeated with the subject in a standing and supine position. Mean perfusion (arbitrary perfusion units) for individual teeth varied from 2.7 for a central incisor to 15.5 for a lateral incisor. Perfusion was greatest for lateral incisors and least for central incisors. Pulpal perfusion was significantly higher in a supine than in a standing or sitting position. Initial clinical experience with LDF encourages further investigation of its potential as a diagnostic tool for determining pulp vitality. Preliminary experimental results suggest that LDF will be a valuable source indicating pulpal response to orthodontic therapy with fixed appliances.

Relationship between arterial pressure and blood flow in the generation of slow-wave flowmotion in rat skeletal muscle

The objective of this study was to determine the role of hypotension and hypoperfusion in the induction of regular slow-wave flowmotion (SWFM) in skeletal muscle in vivo. SWFM and microcirculatory muscle blood flow (MBF) were assessed by laser Doppler flowmetry in anesthetized rats exposed to: (1) graded hemorrhage (n = 15); (2) partial occlusion of the feeding artery (n = 6); (3) partial occlusion of the vein (n = 6), and (4) the vasodilator hydralazine (n = 10). Mean arterial pressure (MAP) was significantly reduced to 65 +/- 2.1% after hemorrhage and hydralazine before (64 +/- 2.4%) and after (42 +/- 1.8%) additional blood loss, but remained unchanged after venous occlusion. The pressure of the feeding artery fell to 38 +/- 1.2% after partial occlusion. MBF dropped significantly to 74 +/- 4.2% after hemorrhage, 54 +/- 5.6% after arterial and 53 +/- 3.0% after venous occlusion. Hydralazine caused MBF to rise to 192 +/- 21.8% before additional blood withdrawal and returned to normal values after it. SWFM was observed in all animals after hemorrhage and arterial occlusion, but in none after venous occlusion. In the hydralazine group, SWFM occurred only after blood loss. The hemoglobin concentration was reduced to 82 +/- 2.1% after hemorrhage. It remained normal after hydralazine administration, but decreased to 79 +/- 1.2% after the subsequent blood withdrawal. We conclude that arterial hypotension, but not hypoperfusion, induces SWFM, and hyperperfusion prevents it. Our results support the hypothesis that SWFM is generated by a reduction of vascular wall tension.

Pathophysiological role of secretory type I and II phospholipase A2 in acute pancreatitis: an experimental study in rats

BACKGROUND

In human acute pancreatitis two different types of secretory phospholipase A2 (PLA2) have been found.

AIM

To analyse the specific pattern of distribution of these PLA2 activities and their pathophysiological role in experimental acute pancreatitis.

SUBJECTS AND METHODS

Catalytic activities of secretory type I (pancreatic) and type II (non-pancreatic) PLA2 and the protein concentration of immunoreactive pancreatic PLA2 (IR-PLA2) in serum and pancreatic tissue of rats with cerulein (mild form) and sodium taurocholate (severe form) induced acute pancreatitis were determined.

RESULTS

Cerulein infusion caused a significant increase in type I PLA2 activity (p < 0.01) and IR-PLA2 protein concentration (p < 0.01) in serum and pancreas, whereas type II PLA2 activity remained unchanged during the 12 hour observation period. Histology showed no significant tissue destruction. In sodium taurocholate induced acute pancreatitis type II PLA2 activity significantly increased, reaching values over 10-fold higher than controls (p < 0.01), whereas IR-PLA2 protein concentration and type I PLA2 activity were only marginally increased. In this severe model of acute pancreatitis significantly lower values were detected than in the control pancreas (p < 0.002) for PLA2 activity and IR-PLA2 protein concentration. Histology showed parenchymal and fat necroses with haemorrhage, oedema, and inflammatory cell infiltration.

CONCLUSIONS

Type I PLA2 activity is dependent on the IR-PLA2 protein concentration in serum and pancreatic tissue. The type II PLA2 activity is not stimulated by cerulein, which indicates an extra-acinar origin of this enzyme. Type II PLA2 activity is significantly increased in sodium taurocholate induced acute pancreatitis indicating its role in the local necrotising process and involvement in the systemic effects in severe acute pancreatitis.

Effect of hepatic nerve stimulation and norepinephrine on the laser Doppler flux signal from the surface of the perfused rat liver

The effect of hepatic nerve stimulation and norepinephrine (NE) on the laser Doppler signal from the surface of the perfused rat liver was tested. The livers from male Wistar rats were perfused in situ via the portal vein with Krebs-Henseleit buffer containing 20% bovine erythrocytes (37 degrees C, pH 7.4) and total liver blood flow (TLBF) was by timed collection of effluent. Portal vascular resistance (PVR) was calculated from the pressure difference across the liver. Linearity of laser Doppler flowmetry (LDF) with TLBF was confirmed in all preparations. Stimulation of the hepatic nerves (2 ms, 20 V) was performed at frequencies between 0.5 and 20 Hz (n = 11). NE was added to the buffer at concentrations between 10(-10) and 10(-6) M (n = 8). A stimulus-dependent rise in PVR occurred during hepatic nerve stimulation (basal, 3.11 +/- 0.26 dyn s cm-5) and NE administration (basal, 2.62 +/- 0.29 dyn s cm-5), with a maximum effect at 20 Hz (311 +/- 45%) and 10(-6) M (591 +/- 72%), respectively. Both LDF and TLBF fell during nerve stimulation and NE. A linear relationship (r = 0.99; p < 0.001) between change in TLBF (%) and LDF flux (%) was found for NE (10(-10) to 10(-6) M). During nerve stimulation, the fall in TLBF and LDF flux was linear with the logarithm of stimulus frequency and reached a maximum at 10 and 20 Hz, respectively. At a stimulus frequency of 20 Hz, the change in LDF was significantly different from the change in TLBF (p < 0.001). We conclude from our findings that during high-frequency hepatic nerve stimulation, LDF underestimates TLBF.

Haemorrhage during anaesthesia and surgery: continuous measurement of microcirculatory blood flow in the kidney, liver, skin and skeletal muscle

Multichannel laser Doppler flowmeters allow continuous, simultaneous measurement of perfusion in several organs. We measured microcirculatory blood flow in the kidney, liver, skin and skeletal muscle in 10 anaesthetized rats subjected to abdominal surgery and graded haemorrhage (withdrawal of 5% total blood volume every 10 min). Mean arterial blood pressure, heart rate and haemoglobin concentrations were also measured. Muscle blood flow decreased after only 10% blood loss, but without significant changes in the other organs. At this time the perfusion signal from the muscle was cycling 2-3 times per min (slow wave flowmotion) which was never seen in any other organ. After 35% blood loss, all organs monitored maintained approximately 70% of initial flow, despite a 45% decrease in mean arterial pressure from 104 +/- 12 to 55 +/- 9 mmHg (mean +/- SD). After 40% blood loss there was a sharp decrease in blood flow in all organs. Haemoglobin concentration decreased from 14.4 +/- 0.8 to 10.8 +/- 1.3 mg dL-1 after 45% blood loss. We conclude that laser Doppler flowmetry is useful for continuous measurement of microcirculatory blood flow in several organs simultaneously during haemorrhagic hypovolaemia. It showed that microcirculatory blood flow in skeletal muscle is particularly sensitive to lesser degrees of blood loss during anaesthesia. Hypovolaemia-induced slow wave flowmotion occurred only in skeletal muscle, which may be linked to fluid mobilization during haemorrhage.

Effect of orthotopic transplantation of liver on systemic and splanchnic hemodynamics in conscious rat

The long-term cardiovascular effects of orthotopic liver transplantation (OLT) were studied in conscious Lewis rats with a radioactive microsphere technique. Three months after OLT with an all-suture technique for graft revascularization (s-OLT), all hemodynamic parameters were similar to control. OLT with "cuffs" fitted to the portal vein and infrahepatic inferior vena cava (c-OLT) led to prominent hemodynamic disturbances including 1) hyperkinetic circulation with increased cardiac index (CI; 22%; P < 0.05) and decreased mean arterial pressure (15%; P < 0.05) and total peripheral resistance (TPR; 28%; P < 0.05); 2) a slight increase in portal pressure (11.8 +/- 0.9 vs. 9.3 +/- 1.7 mmHg in control) and marked portal-systemic shunting (51 +/- 11 vs. 0.05 +/- 0.04% in control; P < 0.05); 3) increased hepatic arterial blood flow (0.49 +/- 0.06 vs. 0.27 +/- 0.04 ml.min-1.g liver wt-1; P < 0.05); 4) splanchnic vasodilation with vascular resistance significantly (P < 0.05) lower in the liver, stomach, and large intestine; and 5) increased blood flow and decreased vascular resistance in the kidneys and heart. Ganglionic blockade with chlorisondamine (5 mg/kg body wt iv) indicated that the increase in CI seen in the c-OLT rats was probably sympathetically mediated, whereas the increase in renal blood flow was a reflection of the increase in CI. After ganglionic blocker administration, TPR and regional vascular resistances decreased to approximately the same extent in the control and c-OLT groups, indicating that vascular sympathetic tone was unchanged in the c-OLT rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Regression of bile duct damage and bile duct proliferation in the non-rearterialized transplanted rat liver is associated with spontaneous graft rearterialization

The aim of this study was to investigate the long-term consequences of non-rearterialization of the graft in rat liver transplantation. Liver transplantation with (AOLT) and without graft rearterialization (NOLT) was performed in anesthetized male Lewis rats. Quantitative morphometry and semiquantitative histopathology of the liver were performed at various times after operation. Volume fractions of tissue components were determined. The number of arteries and bile ducts per portal tract were measured in histological sections from both groups. Hepatic blood flow was measured using the radioactive microsphere technique in rats after NOLT (6 months). AOLT livers had a preserved lobular architecture at all time points and unaltered volume fractions. In addition, AOLT livers maintained approximately one artery and one bile duct per portal tract after transplantation. NOLT livers showed bile duct damage at 3 days, cellular infiltration and ductular proliferation at 1 week, increased ductular proliferation at 4 weeks, and fibrosis at 6 months. The volume fractions for nonhepatocyte parenchyma (3 days, 19.14 +/- 1.29; 1 week, 20.44 +/- 1.76; 4 weeks, 15.46 +/- 3.14), bile ducts/ductules (1 week, 4.88 +/- 1.07; 4 weeks, 7.20 +/- 2.42), and connective tissue (4 weeks, 4.02 +/- 1.66; 6 months, 14.94 +/- 0.63) were significantly increased. Hepatocyte volume fraction was significantly decreased at all time points. A total of 1.58 +/- 0.08 arteries/portal tract were found in NOLT livers after 4 weeks, rising to 2.44 +/- 0.10 arteries/portal tract after 6 months. At 6 months, hepatic arterial blood flow (0.69 mL/min/g) was significantly higher (P < .02) than control (0.25 mL/min/g).(ABSTRACT TRUNCATED AT 250 WORDS)

The influence of flow and hematocrit on the laser Doppler flux signal from the surface of the perfused pig liver

OBJECTIVE

We tested the hypothesis that the measurement volume of the laser Doppler flowmeter (LDF) is too small to provide reliable quantitative estimates of total liver blood flow of large mammals, such as the pig.

METHODS

In a perfused pig liver, the influence of changing (i) hepatic arterial (HA) and portal venous flows individually (n = 9), (ii) HA flow at fixed portal venous flow (50%, 70%, and 100% expected total liver blood flow), and (iii) hematocrit (0-30%) at fixed total liver blood flow on LDF flux was tested (n = 8).

RESULTS

Linearity of LDF with hepatic arterial flow and portal venous flow was confirmed; however, the slope of the regression lines was higher for hepatic artery [1.92 +/- 0.60 (SD)] than portal vein perfused livers (0.66 +/- 0.34; P < 0.001). With portal venous flow at 50% and 70% total liver blood flow, changing hepatic arterial flow produced linear LDF versus flow responses, but at 100% total liver blood flow, linearity was achieved in only 6/9 livers. The coefficient of variation for the slopes of regression lines was always > 30%. At constant total liver blood flow (100 ml/min per 100 g), LDF response decreased linearly by a factor of about 2 on changing the hematocrit from 30% to 5% and markedly fell as the hematocrit was further decreased to zero.

CONCLUSIONS

These results suggest that (i) the LDF flux signal from the liver surface provides a poor measure of hepatic microcirculatory blood flow during changes in total liver blood flow as the LDF responds with about three times greater sensitivity to changes in hepatic arterial than in portal venous flow, and (ii) when hematocrit is falling, LDF may underestimate hepatic perfusion to a significant extent. In addition, due to high measurement variability, the LDF flux signal cannot be quantified in absolute perfusion units.

Redistribution of portal venous but not hepatic arterial flow is induced by hepatic nerve stimulation in the perfused rat liver

The effects of hepatic nerve stimulation, norepinephrine and 6-hydroxydopamine (6-OHDA) on hepatic hemodynamics were investigated in rat livers perfused in situ via both the portal vein and hepatic artery. Nerve stimulation caused a significant fall in total liver blood flow and an increase in portal and arterial pressures. Norepinephrine and 6-OHDA in addition to causing a fall in flow caused significant pressure increases in the bed perfused (arterial or portal). Under basal conditions, the inter- and intra-lobar distribution of microspheres (113Sn- or 57Co-labelled) introduced via the portal vein or via the hepatic artery was homogeneous in all 6 liver lobes. During nerve stimulation, homogeneity of interlobular microsphere distribution was maintained. However, the intralobar distribution of microspheres introduced via the portal vein displayed a significant redistribution from the periphery to the core of each of the four largest lobes studied (p < 0.05). In contrast, when microspheres were introduced via the hepatic artery, there was no universal redistribution of microspheres with only one lobe demonstrating a significant decrease in flow to the periphery (p > 0.05). Infusion of norepinephrine (10(-8) M) or 6-OHDA (1 mg.kg-1 body weight) via either the hepatic artery or the portal vein was without effect on the intrahepatic distribution of the microspheres. We conclude from our results that during hepatic nerve stimulation there is a significant redistribution of portal venous but not hepatic arterial flow from the periphery to the core of the liver lobe. The persistence of hepatic arterial flow during nerve stimulation may represent a protective mechanism by which the periphery of the liver, especially the bile ducts, remains perfused during a reduction in total liver blood flow.

Continuous perioperative monitoring of microcirculatory blood flow in pectoralis musculocutaneous flaps

Hypovolemia and hypotension in traumatized patients as well as those undergoing long-lasting surgical procedures lead to hypoperfusion of tissues. Combined with the trauma of flap elevation and the warm ischemia during performance of the anastomoses, hypoperfusion of flap tissues may lead to flap failure. The influence of hypovolemia, ischemia and reperfusion on flap macro- and microcirculation was studied in an acute experiment on a new musculocutaneous pectoralis flap developed in minipigs. Using a multichannel laser Doppler system we studied, simultaneously and continuously, microcirculatory flow (MBF) in both the skin and muscle of the flap as well as in the contralateral control skin and muscle in anesthetized minipigs (n = 7). Measurements were done before and after raising the flap, after 90 min of flap ischemia, during mild to moderate hypovolemia (5%, 10%, 15%, and 20% blood loss) and during and after restoration of blood volume. Electromagnetic flowmetry was used to measure total blood flow (TBF) to the flap. All animals remained hemodynamically stable during the experiment. The flap MBF decreased by 20% in the skin and 25% in the muscle after flap elevation with no changes in the control skin and muscle. After flap ischemia and reperfusion, MBF returned to post-elevation values while TBF showed a significant increase as compared to MBF (P < 0.05). Hypovolemia caused a gradual drop in cardiac output (25%) and mean arterial pressure (40%), but both recovered above the baseline after reinfusion of shed blood. Hypovolemia also caused a 60% reduction in MBF in both flap skin and muscle, and only 20-23% in control skin and muscle (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Randomized trial of duodenum-preserving pancreatic head resection versus pylorus-preserving Whipple in chronic pancreatitis

BACKGROUND

In about 30% of patients, chronic pancreatitis leads to an inflammatory enlargement of the pancreatic head with subsequent obstruction of the pancreatic duct, common bile duct, and duodenum.

METHODS

In a prospective, randomized controlled trial, we compared duodenum-preserving pancreatic head resection (DPPHR) with pylorus-preserving Whipple (PPW) operation to define the advantages of each operation with regard to (1) postoperative complications, (2) glucose tolerance and induction of diabetes mellitus, and (3) postoperative pain and quality of life up to 6 months after operation for chronic pancreatitis.

RESULTS

The two study groups of 20 patients were both well balanced with regard to sex, age, history of chronic pancreatitis, and indication for surgery. Postoperative mortality was zero. After duodenum-preserving and pylorus-preserving resection, morbidity was 15% and 20%, respectively. After 6 months, patients who underwent the duodenum-preserving resection had less pain, greater weight gain, a better glucose tolerance, and a higher insulin secretion capacity.

CONCLUSION

The DPPHR compares favorably with the standard PPW operation and should be considered as an alternative procedure in the treatment of chronic pancreatitis.

Effects of halothane and isoflurane anaesthesia on microcirculatory blood flow in musculocutaneous flaps

Hypoperfusion and necrosis in musculocutaneous flaps used for reconstruction of tissue defects is still a significant clinical problem. Although the causes of hypoperfusion are frequently surgical in nature, little is known about the effects of anaesthetic management on blood flow in flaps or the outcome of flap surgery. We compared in minipigs the effects of halothane and isoflurane anaesthesia in equipotent doses on microcirculatory blood flow (MBF) in the skin and muscle part of musculocutaneous flaps and also in intact (control) skin and muscle. Measurements were made during stable normovolaemic conditions and during mild to moderate hypovolaemia (withdrawal of 5%, 10% and 15% of total blood volume). Multi-channel laser Doppler flowmetry (LDF) was used to measure MBF and electromagnetic flowmetry (EMF) for total flap blood flow. During normovolaemic conditions there was no significant difference between the two groups in central haemodynamic or respiratory data. After 15% blood loss, however, there was a significant decrease in mean arterial pressure and cardiac output in the halothane group while there was no significant change in the isoflurane group (P < 0.05). MBF in control skin, control muscle and flap muscle remained approximately 10-15% higher in the isoflurane than in the halothane group throughout the study. In the isoflurane group, MBF in flap skin was unchanged during normovolaemia and there was less than 10% decrease during hypovolaemia. In the halothane group hypovolaemia caused a significant decrease in MBF in flap skin: 27% decrease after 5% blood loss, 45% decrease after 10% blood loss and 49% decrease after 15% blood loss compared with 5%, 20% and 21%, respectively, in intact skin.(ABSTRACT TRUNCATED AT 250 WORDS)

Laparoscopic liver resection in the Large White pig--a comparison between waterjet dissector and ultrasound dissector

Resection of 16 liver lobes was successfully undertaken laparoscopically in anaesthetised Large White pigs. These animals proved to be suitable for the instruments used in human laparoscopic procedures. It was planned to undertake a comparison between the waterjet and ultrasound dissectors, but this proved impossible because of the development of a thick intraabdominal mist during dissection with the waterjet dissector. The ultrasound dissector was effective in dissecting the intraparenchymal hepatic structures, especially the portal vein and the hepatic vein. These blood vessels were safely secured with endoclips, while bleeding points on the resection surface were coagulated with an argon beam coagulator. The liver specimens removed were approximately 75 g in weight. All ultrasound-dissected animals survived for 10 days. Post-mortem evaluation showed two cases of wound infection, one case of subphrenic abscess and two cases of biloma. Our results emphasise the potential of laparoscopic resection techniques for formal or at least peripheral liver resections in humans.

Portal hypertension promotes bacterial translocation in rats mono- and non mono-associated with Escherichia coli C25

The basis for the high incidence of infectious complications in portal hypertension (PHT) remains unclear. The hypothesis that PHT induces bacterial translocation (BT) was tested in a rat model with or without mono-association with streptomycin resistant Escherichia coli C25 and with or without hypovolemic shock. PHT was achieved by partial portal vein ligation and three weeks later hypovolemic shock (HS) was induced. Blood, liver, spleen and mesenteric lymph nodes cultures were performed twenty-four hours later. PHT promoted BT to mesenteric lymph nodes in indigenous flora (4/6 [67%]) and mono-associated animals (7/9 [78%]) compared to sham laparotomy and sham shock (SL + SS) animals (0/6 [0%] and 2/9 [22%] respectively) (p = 0.03). The combination of PHT and HS resulted in increased mortality in mono-associated (7/15 [47%]) and non mono-associated animals (8/15 [53%]). No significant translocation was noted in liver and spleen and bacteremia was found only in the PHT + HS mono-associated animals (4/8 [50%]). PHT induces BT to mesenteric lymph nodes and this may account for the high incidence of septic complications associated with PHT. In this model, the addition of HS to PHT leads to an increased mortality but without uniform translocation of the gut flora beyond mesenteric lymph nodes.

Influence of age on the cardiovascular response during graded haemorrhage in anaesthetized rats

The present study was designed to follow the cardiovascular response to graded haemorrhage in two groups of adult rats of different ages. Group A (n = 10) had a mean body weight (bwt) of 655 g (50 weeks old) and group B (n = 10) had a mean bwt of 250 g (12 weeks old). After induction of anaesthesia, the carotid artery was cannulated for continuous intra-arterial blood pressure monitoring and for controlled haemorrhage. Five per cent of the total blood volume (TBV) was removed every 15 min until a maximum of 50% was reached. Mean arterial pressure (MAP) fell by 4-9 mm Hg each time 5% TBV was removed in both groups, and at the end of the study the MAP was comparable in the two groups (34 +/- 10 mm Hg in group A and 28 +/- 8 mm Hg in group B). There were no significant changes in heart rate (HR) in the young animals during haemorrhage, while there was a significant drop in heart rate in the older animals when blood loss exceeded 15% of TBV (P < 0.05). A significant difference was also observed in HR between the two groups of animals with blood loss in excess of 20% TBV (P < 0.05). It was concluded that although the hypotension induced by graded haemorrhage was similar in young and old rats, the older animals were less able to maintain their HR, probably as a consequence of age- and anaesthetic-related changes in sympathetic activity.

Acute effects of partial hepatectomy on liver blood flow in the jaundiced rat

The aim of this study was to define the effects of hepatic resection on liver blood flow and portal pressure in the presence of obstructive jaundice. Liver blood flow and portal pressure were measured in 17 jaundiced animals (5 days bile duct ligation) and 16 control animals. A 70% liver resection with or without hepatic artery ligation was performed in the control animals. On day 5, the animals underwent a second operation. Hepatic artery ligation alone was performed in a group of control animals. In jaundiced rats there was a decrease in liver blood flow (1.24 +/- 0.23 ml/min per g vs. normal 1.91 +/- 0.38 ml/min per g, P < 0.01) and an increase in portal pressure (11.2 +/- 3.47 mmHg vs. normal 6.93 +/- 1.01 mmHg, P < 0.01). After partial hepatectomy, a significant increase in liver blood flow was observed in controls (2.44 +/- 0.74 ml/min per g, P < 0.01) but not in jaundiced rats. Hepatic artery ligation did not affect blood flow or portal pressure either before or after resection. Small but significant portal-systemic shunting was found in all jaundiced rats (2.19 +/- 2.1% vs. 0.026 +/- 0.015%, P < 0.05). These results demonstrate that partial hepatectomy results in a significant increase in total liver blood flow. Acute cholestasis appears to prevent this increase. Even in the early stages of obstructive jaundice in the rat, there were signs of portal-systemic shunts.

Effect of orthotopic transplantation and chemical denervation of the liver on hepatic hemodynamics in the rat

The involvement of the sympathetic nervous system in the control of basal hepatic hemodynamics was investigated. Hepatic denervation was achieved by orthotopic transplantation or chemical denervation of the organ. In male Lewis rats, transplantation with rearterialization of the graft was performed. Chemical denervation was achieved by intraportal injection of 6-hydroxydopamine (75 mg/kg). Normal liver physiology was confirmed by histology and liver function tests. Four weeks post-transplantation and 7 days post-denervation, histological examination revealed no differences between transplanted, denervated and untreated or sham-operated control animals. Liver function measured by standard tests (e.g., plasma SGOT, bilirubin) was normal in all groups. The rate constants for aminopyrine breakdown in transplanted (0.015 +/- 0.005 min-1), denervated (0.015 +/- 0.0012 min-1) and control rats (0.015 +/- 0.001 min-1) were not significantly different. No significant difference in the rate of galactose breakdown was found. Total liver blood flow (measured by the 133Xe clearance technique in the anesthetized animal) was unaffected by transplantation (rate constant, 0.245 +/- 0.062 min-1; control 0.279 +/- 0.011 min-1). The interlobular distribution of portal blood flow was tested by intraportal injection of 51Cr-labelled microspheres. A linear relationship between flow to lobe and lobe size was confirmed in control (r = 0.95), denervated, (r = 0.99) and transplanted rats (r = 0.97) and the 'relative' flow to each lobe was not significantly different in the 3 groups. No significant differences in the 'core' to 'periphery' distribution of portal blood flow were found in the 3 groups. A small but significant portal systemic shunt was found in transplanted but not denervated or control animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Manometry of esophageal varices: comparison of an endoscopic balloon technique with needle puncture

BACKGROUND

A noninvasive technique of pressure measurement in esophageal varices using an endoscopic balloon has been shown to be reliable in vitro. In the present study, this method was tested in vivo.

METHODS

Thirty-seven pressure measurements in esophageal varices were performed in 34 patients by two independent operators (A and B) using an endoscopic balloon and compared with measurements performed by needle puncture by a third operator (C).

RESULTS

Three measurements performed with the endoscopic balloon were rejected because they were noninterpretable. Measurements performed by A and B correlated well (correlation coefficient, 0.90); interobserver variability (r) was 0.88. Of 37 punctures performed for pressure measurements, 4 resulted in bleeding and 8 measurements were rejected as uninterpretable. Regression analysis showed a good correlation between the needle puncture and balloon techniques for pressure measurements performed by both operators (y = 5.3 + 1.0x, r = 0.8; y = 6.2 + 0.9x, r = 0.8), and analysis of variability showed a measurement bias of -5.3 +/- 4.1 and -4.1 +/- 3.5 cm H2O. No significant difference in variceal size measured with the endoscopic balloon or endoscopic forceps was found.

CONCLUSIONS

The endoscopic balloon allows measurement of pressure in esophageal varices without hazard to the patient; in addition, it may be used to assess the varix size.

Effect of orthotopic liver transplantation and chemical denervation of the liver on the activities of hepatic monoamine oxidase and catechol-O-methyltransferase

The denervation of some tissue is associated with a fall in the activities of monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT). Here we report on the effect of orthotopic liver transplantation and chemical denervation of the liver on the enzymes. Liver transplantation was performed on Lewis rats (n = 7). Denervation (n = 8) was by intraportal injection of 6-hydroxydopamine (75 mg/kg). A control group (n = 8) was also included. The norepinephrine content of the transplanted and denervated livers was reduced by greater than 99% (P < 0.001) and 95% (P < 0.001), respectively. The activity of hepatic COMT (substrate: catechol [5 mM] was not affected by transplantation or denervation. The activity of MAO with 0.1 mM 5-hydroxytryptamine (5-HT) (substrate for MAO-A) and with 0.01 mM 2-phenylethylamine (substrate for MAO-B) were not affected by denervation. In the transplanted liver, the activity of MAO with 5-HT and 2-phenylethylamine was increased by 26% (P < 0.05) and by 53% (P < 0.001), respectively. The ratios of the activities of the A to B forms of MAO (approximately 70% A to 30% B) was not affected by either procedure. Enzyme sensitivity for MAO inhibitors clorgyline and deprenyl were not significantly altered by transplantation. The concentration of plasma norepinephrine in the transplantation group was significantly lower than either the control (P < 0.001) or denervation groups (P < 0.05). We conclude from our results that the metabolism of circulating catecholamines by the liver is unlikely to be impaired after liver transplantation.

Interpretation of the laser Doppler flow signal from the liver of the rat

It has been proposed that the laser Doppler flow (LDF) signal from the surface of the rat liver is almost exclusively a measure of hepatic arterial and not of total liver blood flow and therefore that LDF is not a suitable technique for the measurement of blood flow in the hepatic microcirculation. The objective of the present study was twofold: (i) to establish that liver blood flow is homogeneously distributed and (ii) to assess the behavior of the LDF signal during changes in hepatic perfusion. When 51Cr-labeled microspheres were injected into the portal vein (n = 12), no significant differences in the relative flow (cpm/lobe to cpm/liver) to each of the liver lobes were found nor was there any difference in the ratio of flow to the outer 1-2 mm of lobe as compared to that to the "core" of the liver. Temporary occlusion of the hepatic artery and the portal vein caused approximately 13% (n = 7, P < 0.001) and approximately 74% (n = 7, P < 0.001) fall in LDF signal, respectively. Diversion of flow from the anterior to the posterior lobes (n = 5) caused a 97.9 +/- 21.1% (SD, P < 0.001) rise in LDF signal in the posterior lobes. Zero-flow LDF signal was found to represent 13.0 +/- 4.1% of maximum. Hemorrhage (in 1.5-ml aliquots) was associated with a fall in mean arterial pressure (MAP) and LDF signals. A linear relationship between MAP and the LDF signal (r > 0.9) was found. Reinfusion of blood caused both MAP and the LDF signal to return to normal. We conclude that (i) blood flow in rat liver is homogeneously distributed; (ii) the LDF signal from the liver surface responds in a manner predicted by conventional theories of hepatic hemodynamics during alteration, either independent or combined, in hepatic arterial and portal venous blood flow; and (iii) LDF may be used to measure relative changes in hepatic perfusion but problems associated with zero-flow signal and intersite variability preclude its quantification in absolute flow units.

Morphometry of the liver after liver transplantation in the rat: significance of an intact arterial supply

Two models of orthotopic liver transplantation in the rat currently used are with and without reconstruction of the hepatic artery. The aim of this study was to assess the importance of the arterial blood supply to liver structure after orthotopic liver transplantation with advanced morphometric methods. Orthotopic liver transplantation was performed in male Lewis rats, of which 11 underwent reconstruction of the hepatic artery and 11 did not. A group of untreated controls (n = 5) and a group of animals with hepatic artery ligation (n = 4) were included. Eight weeks after surgery liver tissue was harvested and subjected to systematic random sampling. A point-counting method was used, volume fractions of tissue components were determined. Liver samples from rats that underwent hepatic artery reconstruction had preserved lobular architecture, and estimated bile duct (0.71% +/- 0.33% [S.D.]) and connective tissue (1.89% +/- 0.52%) volumes were not significantly different from those of controls (bile duct, 0.34% +/- 0.17%; connective tissue, 0.70% +/- 0.07%). In contrast, liver samples from rats that did not undergo hepatic artery reconstruction showed bile duct proliferation (7.19% +/- 4.83%; p < 0.05) and an increase in connective tissue volume (7.54% +/- 3.68%; p < 0.05) associated with a decrease in hepatocyte volume (controls, 87.3% +/- 0.3%; rats that underwent arterialization, 85.5% +/- 1.0%; rats that did not undergo arterialization, 73.2% +/- 8.2% [p < 0.05]). Interestingly, hepatic artery ligation had no significant effect on any parameter.(ABSTRACT TRUNCATED AT 250 WORDS)

Selective sympathectomy of the liver: a comparison of orthotopic liver transplantation and intraportal 6-hydroxydopamine injection

1. Tissue noradrenaline (NA) levels correlate well with the extent of sympathetic innervation of that tissue. 2. In this study the distribution of NA throughout the different lobes of the rat liver was studied. The extent of sympathectomy by means of either orthotopic liver transplantation (OLT) (n = 7) or chemical denervation by intraportal administration of 6-hydroxydopamine (6-OH-DA) (n = 8) was examined. 3. In the normally innervated rat liver, NA was homogeneously distributed throughout the organ. Tissue NA was decreased both by OLT (> 99%) and 6-OH-DA (93%) (both P < 0.001 versus control). 4. Samples of the renal cortex and left ventricle were taken as reference tissues. OLT did not result in any change in reference tissue NA, however, 6-OH-DA decreased renal cortex NA by 93% and ventricular NA by 76%, respectively (both P < 0.01 versus OLT). 5. We conclude that OLT causes selective and complete hepatic sympathectomy but that 6-OH-DA causes incomplete denervation of the liver and significant denervation of other organs.

Orthotopic liver transplantation in the rat: comparison of models with and without rearterialization of the graft

A total of 112 orthotopic liver transplants with (AOLT) and without (NOLT) rearterialization were performed in 2 series using male Lewis rats as donors and recipients. In the first series, the 2-week survival rates were 5/11 (45.5%) in the NOLT group and 22/31 (71%) in the AOLT group. The difference in survival was due to operative experience, as the NOLT transplants were performed before the AOLT transplants. In the second series, the NOLT (n = 30) and AOLT transplants (n = 40) were performed in random order. No differences in 2-week survival rates were found [NOLT, 29/30 (96.7%); AOLT, 37/40 (92.5%)]. Recovery of pre-operative body weight was, however, faster in the AOLT (7 days) than in the NOLT group (14 days). In the NOLT group, elevation of serum levels of GOT (p < 0.05 vs. AOLT at 3 days) and alkaline phosphatase (p < 0.01 vs. AOLT at 3 days and 1 week; p < 0.05 at 4 weeks) were found. We conclude from our results that in OLT without prolonged graft storage, survival is a sensitive marker of operative success only in the training phase. Once operative technique has been mastered, a success rate of greater than 90% should be achieved before inclusion of the animals in further scientific studies. As the AOLT animals recover body weight faster and have less evidence of liver injury up to 4 weeks post-transplantation, one is led to the conclusion that AOLT in the rat may be a better model for use in all liver transplantation research.

Measurement of hepatic perfusion in rats by laser Doppler flowmetry

Little is known about the performance of the laser Doppler flowmeter (LDF) with changes in flow characteristics in the hepatic microcirculation. Red blood cell (RBC) flux, as measured by LDF, is sensitive to alterations in RBC velocity and RBC concentration, and both parameters must be considered when evaluating the technique. In vitro, linearity of LDF signal with RBC velocity up to 4 mm/s (r greater than 0.99) and RBC volume fractions up to 1.5% were demonstrated (r greater than 0.98). At higher velocities and volume fractions, RBC flux was underestimated. In portally perfused rat liver, LDF output was linearly related to total liver blood flow (TLBF; r greater than 0.9) for perfusate hematocrits between 2.5 and 40%, although the slope varied between preparations. At constant TLBF (2 ml.min-1.g-1), the LDF output changed linearly with perfusate hematocrit up to 20% (r greater than 0.99) but underestimated the increase at 40%. These results suggest that the LDF responds linearly to velocity-mediated flow changes but that it may underestimate a change if mediated through alteration in tissue RBC concentration. With hepatic nerve stimulation, TLBF fell to 51 +/- 14% of prestimulation (P less than 0.001), whereas the LDF output and superficial flow measured by 85Kr clearance fell to 12 +/- 10 and 14 +/- 10% (both P less than 0.01 vs. TLBF), respectively, suggesting that the LDF may be used to follow rapid flow changes in the periphery of the liver.

Experimental evaluation of an endoscopic balloon for manometry of esophageal varices

Measurement of pressure in esophageal varices may be performed using an endoscopic balloon technique. Improvements in this technique are described, and a complete experimental assessment of its potentials and limitations using an in vitro model consisting of an artificial esophagus containing a water-filled tube (varix) is reported. The influence of the varix diameter (3, 5, and 7 mm) and wall thickness (0.031, 0.144, and 0.256 mm) and the possible effect of the elasticity or peristalsis of the esophageal wall were investigated. Four hundred eighty pressure measurements were performed between 5 and 40 cm H2O. Linear regression analysis showed a good correlation between the pressure in the varix and that measured endoscopically (r greater than 0.9). No obvious measurement bias was found for any of the varices. Variability in pressure measurement was low in all thin-walled varices, and only in a 3-mm thick-walled varix was it found to be high [lower limit, -11.2 (1.4) cm H2O; upper limit, 6.4 (1.4) cm H2O]. Pressure measurement in a 7-mm varix was not affected by simulated peristalsis or esophageal wall elasticity. Intraobserver and interobserver reliability of measurement assessed in a series of 324 pressure measurements by three endoscopists was excellent. The authors conclude that this method may give reliable results in large and medium-sized varices and may be unaffected by peristalsis or esophageal wall elasticity. However, further assessment in vivo remains necessary.

The effect of haloperidol, spiperone and dantrolene on the concentrations of creatine phosphate, ATP and lactate in brain and skeletal muscle of the rat during halothane anesthesia

The concentrations of creatine phosphate, ATP and lactate were measured in the brain and skeletal muscle of rats under halothane anesthesia (1 to 2% in oxygen) and in animals either premedicated with haloperidol or spiperone (200 mg kg-1 and 2 mg kg-1) or treated with dantrolene (860 mg kg-1). Haloperidol and spiperone had no effect on ATP or lactate in skeletal muscle, but caused more than a 30% increase in the concentration of creatine phosphate (p less than 0.01). With dantrolene, an 80% increase in creatine phosphate (p less than 0.0001) and a significant decrease in lactate (p less than 0.0001) were found. Haloperidol caused a significant decrease in brain creatine phosphate concentration (p less than 0.05) while at a dosage of 2 mg kg-1, the ATP concentration was higher (p less than 0.05). Spiperone (2 mg kg-1) caused a 19% increase in creatine phosphate (p less than 0.005) as well as a significant decrease in lactate (p less than 0.005). Dantrolene had no significant effect on the concentration of any brain metabolite. Our results indicate that the effect of anesthetics on the concentration of energy metabolites in tissues can be influenced by drug treatment, which may have implications in the choice of an anesthetic regimen to be used in tissue harvesting.