24-hour preservation of isolated rat hearts perfused with pyridoxalated hemoglobin polyoxyethylene conjugate (PHP) solution at low temperature

The perfused swine uterus model: long-term perfusion

BACKGROUND

It has previously been shown that the viability of swine uteri can be maintained within the physiological range in an open perfusion model for up to 8 hours. The aim of this study was to assess medium- to long-term perfusion of swine uteri using a modified Krebs-Ringer bicarbonate buffer solution (KRBB) in the established open perfusion model.

METHODS

In an experimental study at an infertility institute, 30 swine uteri were perfused: group 1: n = 11, KRBB; group 2: n = 8, modified KRBB with drainage of perfusate supernatant; group 3: n = 11, modified KRBB with drainage of perfusate every 2 h and substitution with fresh medium. Modified and conventional KRBB were compared with regard to survival and contraction parameters: intrauterine pressure (IUP), area under the curve (AUC), and frequency of contractions (F).

RESULTS

Modified KRBB showed significantly higher IUP, AUC, and F values than perfusion with conventional KRBB. In group 3, the organ survival time of up to 17 h, with a 98% rate of effective contraction time, differed significantly from group 1 (P < 0.001).

CONCLUSIONS

Using modified KRBB in combination with perfusate substitution improves the open model for perfusion of swine uteri with regard to survival time and quality of contraction parameters. This model can be used for medium- to long-term perfusion of swine uteri, allowing further metabolic ex vivo studies in a cost-effective way and with little logistic effort.

Extracorporeal perfusion of the human uterus as an experimental model in gynaecology and reproductive medicine

Experimental perfusion of various organs has primarily been used in transplantation medicine to study the physiology, pathophysiology and metabolism of tissues and cells. The purpose of this study was to establish an experimental model for the extracorporeal perfusion of the human uterus with recirculation of a modified, oxygenated Krebs-Henselait solution, in comparison with a non-recirculating perfusion system. With consent of the patients we obtained 25 uteri after standard hysterectomy. We performed an isovolumetric exchange of the perfusion medium at different intervals from 1 to 6 h and examined pH, pO(2), pCO(2), lactate, lactate dehydrogenase and creatine kinase by taking arterial and venous samples every hour for 24 h. We found the perfusions to be adequate when maintaining flow rates at 15-35 ml/min and at pressures ranging from 70 to 130 mmHg. Isovolumetric exchange of the perfusate every 3-4 h was the maximum interval to keep pH, the arterio-venous gradients of pO(2) and pCO(2), and the other biochemical parameters in physiological ranges. Examination by light and electron microscopy showed well-preserved features of myometrial and endometrial tissue. However, a 6 h exchanging interval led to increasing hypoxic and cytolytic parameters during the whole perfusion period. X-ray studies using digital subtraction angiography and perfusion studies with methylene blue demonstrated the homogeneous distribution of the perfusion fluid throughout the entire organ.

Intraarterial perfusion of the hindlimb with pyridoxalated hemoglobin polyoxyethylene conjugate solution in anesthetized dogs

To evaluate the potential clinical usefulness of a modified hemoglobin, pyridoxalated hemoglobin polyoxyethylene conjugate (PHP), the hindlimb vascular bed was perfused with PHP solution while monitoring tissue oxygen tension (PtO2) in anesthetized dogs. The hindlimb region was perfused through the external iliac artery with a roller pump at a varying perfusion rate. PtO2 was measured using a PO2-monitoring probe inserted into the gracial muscle. After surgical preparation for perfusion, the iliac arterial flow rate was 19.9 +/- 5.6 ml/min, and baseline PtO2 was 38.4 +/- 1.3 mm Hg. Perfusion with autologous arterial blood with the pump increased PtO2 and perfusion pressure (PP) in a perfusion rate-dependent manner. Perfusion with PHP solution at 20 ml/min decreased PtO2 from the initial baseline level, but an increase in the flow rate to 40-55 ml/min restored or induced an elevation of PtO2. Results demonstrated that PHP solution can deliver oxygen to local tissue and maintain tissue oxygen tension at the same level as autologous arterial blood at a high enough flow rate.

Effects of pyridoxalated hemoglobin polyoxyethylene conjugate on diameter of rat mesenteric arterioles in situ

The effects of exchange transfusion (ET) with a modified hemoglobin (pyridoxalated hemoglobin polyoxyethylene conjugate, or PHP) on endothelium-dependent relaxation of microvasculature were examined in rat mesenteric arterioles using image-splitter television microscopy. To examine the endothelium-dependent relaxation, we applied acetylcholine (ACh) to arterioles preconstricted with norepinephrine (NE) and measured changes in arteriolar diameter. Topical application of NE (6 x 10(-8) to 6 x 10(-6)M) decreased the diameter of the arterioles dose-dependently to a mean of 45% (SE +/- 4%, n = 6) of the control. Topical application of ACh (7 x 10(-8) to 7 x 10(-6)M) increased the diameter of the arterioles preconstricted with NE in a dose-dependent manner and almost fully reversed the NE-induced decrease in diameter. ET with 6% PHP solution (30 ml/kg) induced an increase in the mean arterial blood pressure (MABP) from 117 +/- 5 to 132 +/- 4 mm Hg (n = 6, p < 0.05), with a concomitant decrease in diameter of arterioles, from 22.6 +/- 2.5 to 19.8 +/- 2.7 microns (p < 0.05). The MABP and arteriolar diameter gradually returned to the control level within 30 min after ET. Arteriolar changes in diameter in response to NE and ACh examined 30 min after ET were similar to those of the control. ET with 6% stroma-free hemoglobin (SFH; 30 ml/kg) did not alter arteriolar changes in diameter in response to NE and ACh. Results suggest that circulating PHP and SFH moieties do not interfere with endothelium-derived relaxing factor(s) induced by ACh in rat mesenteric microvasculatures in situ.

Relationship between chemical properties and biological properties of pyridoxalated hemoglobin-polyoxyethylene

Pyridoxalated hemoglobin-polyoxyethylene (PHP) is a conjugate of human hemoglobin with alpha-carboxymethyl, omega-carboxymethoxypolyoxyethylene(POE). This conjugate is selected as an oxygen carrier for blood substitute because it can survive for a long time in the circulation and also it can transport the same amount of oxygen as red cell. Optimization of PHP has been done by changing the degree of the modification and reaction procedures in order to adjust viscosity and colloid osmotic pressure to physiological values. The oxygen carrying capacity was physically evaluated by oxygen equilibrium curves and biologically by an ATP content in perfused isolated liver. Structural relationship of PHP to the binding properties to haptoglobin was studied and the effect of the POE modification on the binding properties was observed when the number of POE per one hemoglobin molecule is over six. Based on the comparative study of solubility of met-PHP and met-SFH, the POE modification was suggested to reduce the toxicity of hemoglobin against organs. Finally physical properties of PHP at low temperature was discussed in relation to organ preservation.