Hepatocellular metabolic change after orthotopic liver transplantation in rats

The hepatocellular metabolic change after liver transplantation following 2 hr cold ischemia was investigated. Of 55 orthotopic liver transplantation in male Wistar rats, 47 animals were sacrificed at 3 hr, and 1, 2, 7 and 30 days to determine hepatic metabolite levels, in the form of adenine nucleotides, lactate and glycogen. Using the other 8 recipients, biochemical examinations were done at 1, 3, 5, 7, 30 and 60 days and metabolic levels estimated at 60 days. The SGOT and SGPT levels decreased gradually after a remarkable increase on the first postoperative day, while the alkaline phosphatase level revealed a peak value at 30 days. All levels recovered to within the normal range in 60 days. The total adenine nucleotide level reached the normal range within 3 hr following the blood reflow and remained at a normal level thereafter. However, all the metabolic levels apart from total adenine nucleotides deteriorated to reach their worst level at 7 days. The results of this investigation indicate that the posttransplanted deterioration of metabolic levels were possibly caused by the imperfect oxygenation due to cellular edema after blood reflow. However, the levels of these metabolites recovered within 60 days after transplantation.

S-adenosylmethionine increases erythrocyte ATP in vitro by a route independent of adenosine kinase

The mechanism by which S-adenosylmethionine (SAM) and adenosine (Ado) increase ATP levels in intact human erythrocytes in vitro has been compared. The use of erythrocytes from healthy controls and from subjects totally deficient in adenine phosphoribosyltransferase (APRT), plus inhibitors of adenosine kinase (AK) and adenosine deaminase (ADA) separately and together, has enabled us to demonstrate that this increment in ATP levels occurred via totally different metabolic routes. The results show that: (i) whilst the Ado-induced increment in ATP was AK dependent, that produced by SAM was independent of AK: and (ii) the SAM-induced increment in ATP was totally dependent on APRT and that some of the increment produced by Ado might also be APRT dependent. The above data are consistent with the metabolism of SAM to ATP by a route recently identified by us whereby ATP is formed from deoxyadenosine: namely binding to the enzyme S-adenosylhomocysteine hydrolase with subsequent release of adenine and further conversion to ATP via APRT.

Impaired polymorphonuclear leucocyte function in patients undergoing hepatectomy: adenylate energy charge and superoxide anion production in relation to hepatic mitochondrial redox state

Patients undergoing hepatectomy have an increased susceptibility to infection. We therefore studied the energy metabolism of the polymorphonuclear leucocyte (PMN), focusing on energy charge and function, especially superoxide anion (O2-) generation, in relation to the hepatic mitochondrial redox state. By labelling the PMN adenine nucleotide pool with radioactive adenine and by superoxide dismutase-inhibitable reduction of ferricytochrome c, the energy charge and O2- production was measured in 18 patients with hepatoma (non-cirrhotic, seven; cirrhotic, 11) undergoing hepatectomy. Their arterial ketone body ratios (KBRs), reflecting the hepatic mitochondrial redox potential, were above 0.7 before operation. After surgery, the 18 patients were divided into two groups: group A, KBR greater than 0.7, n = 10; and group B, KBR less than 0.7, n = 8. The energy charge and O2- release in group B decreased significantly from preoperative values (P less than 0.001 and P less than 0.01 respectively) and when compared with group A (P less than 0.05 and P less than 0.01 respectively). These results suggest that impaired hepatic energy metabolism (KBR less than 0.7) in hepatectomized patients leads to impaired energy charge and O2- production in the PMNs.

Platelet size and function in septic rats: changes in the adenylate pool

Cecal ligation and puncture (CLP) were performed in rats. After 4 hr (early sepsis) and 16 hr (late sepsis), platelet morphology and function were studied. At 16 hr, platelet counts for the CLP group were significantly lower than for the sham-operated control group. Low maximum aggregation rates (MAR) and decreased platelet counts were elicited in platelet-rich plasma with 4 M ADP and 2 micrograms/ml collagen. However, with platelet counts equalized, MAR for the CLP group increased significantly, especially after 16 hr. The platelet-large cell rate and platelet distribution width decreased temporarily at 4 hr, then rose significantly at 16 hr. No significant changes were observed in the mean platelet volume after 4 hr, but there were significant increases after 16 hr. Total adenine nucleotide (TAN) levels within the platelets rose significantly in the CLP group, suggesting the appearance during the late sepsis of large, heavy platelets or adenine nucleotide-rich platelets. The platelet adenylate pool was divided into granular and cytoplasmic fractions, respectively characterized by ADP and ATP increases. However, no septicemia-related differences were noted in the degree of binding between goat antirat fibrinogen and platelet surface glycoprotein IIb/IIIa complex. Internal environment changes in the platelets indicated that during septicemia hyperfunctional or hypersensitive platelets with a latent capacity for active aggregation and release appeared in the circulation. Hypercoagulability in septicemia involves activation of coagulation factors, stimulation of the coagulation cascade, volume changes accompanying increased platelet TAN content, and changes in AN distribution in the two pools. These findings significantly increase our understanding of the transition from the prethrombotic state to thrombosis in septicemia.

Depletion of dense granule nucleotides during storage of human platelets

The energy metabolism of human platelets was studied during storage of platelet concentrates. The platelets were prepared from buffy coats in PVC/DEHP bags and stored for 7 days at room temperature at a concentration of 1.0 x 10(9)/ml with horizontal agitation. The total amount of ATP and ADP decreased with 40% during this storage. This decrease correlated with the disc-to-sphere transformation associated with the loss of platelet viability. During storage, the ability to incorporate 3H-adenosine into metabolic ATP and ADP (45 min at 37 degrees C) decreased with 50%. Via measurement of the specific activity of actin-bound ADP and the amount of incorporated radioactivity into total ATP and ADP, we calculated the content of the metabolic and storage pools of ATP and ADP. The results indicate that the decrease in adenine nucleotide levels during storage was mainly caused by a depletion of ATP and ADP from the storage pool, whereas the metabolic pool remained nearly intact. After 7 days, the ATP:ADP ratio of the storage pool had decreased from 1.0 to 0.3, indicating hydrolysis of ATP. Diadenosine-triphosphate and diadenosine-tetraphosphate (present in the storage pool) decreased with only 30%, and the serotonin content remained nearly constant. Therefore, it is unlikely that the storage pool was completely secreted. Probably, the storage pool of nucleotides serves as an internal supply for maintaining the contents of the metabolic pool of ATP and ADP during storage of platelets.

Adenine nucleotides, serotonin, and aggregation properties of platelets of blue foxes (Alopex lagopus) with the Chediak-Higashi syndrome

Bleeding times, concentrations of serotonin in whole blood, and concentrations of adenine nucleotides as well as aggregation properties of platelets were examined in 18 blue foxes with Chediak-Higashi-like syndrome (CHS) and 16 controls. A claw of each ketamine-sedated fox was cut until bleeding started and the bleeding time was recorded as the time from the first to the last drop. The bleeding time was greatly increased in CHS foxes. Platelet counts of CHS foxes were normal, but aggregation induced by adenosine diphosphate (ADP), serotonin, collagen, and arachidonate was impaired. Adrenaline and serotonin was impaired. Adrenaline and serotonin potentiated the aggregatory effect of ADP on control as well as on CHS platelets. The mean concentration of ADP in CHS platelets was about one-third that in controls, whereas adenosine triphosphate (ATP) was approximately one-half that in controls. Serotonin could not, in most cases, be detected in blood of CHS foxes. These findings suggest that the prolonged bleeding time in the CHS foxes is, at least partly, due to a storage pool deficiency. The drastically reduced, and in some cases absent, aggregation of CHS platelets in response to arachidonate suggests that defective arachidonate metabolism contributes to the impaired hemostasis.

[Effects of the administration of urinary trypsin inhibitor on the morphology and function of platelets in the rat septic models]

Effects of urinary trypsin inhibitor (UTI) on the number, morphology and function of platelets under septic state were studied in rat models of cecal ligation and puncture (CLP). At formation of CLP, 5,000 U/kg/h of UTI was serially administered intraperitoneally and blood was sampled after 16 hours. Comparative study among sham-operation group, CLP group, and CLP + UTI group revealed: 1) inhibition of the platelets of platelet counts and appearance of large-sized, active platelets by UTI in the CLP + UTI group, 2) increase of platelet maximum aggregation rate (MAR) by ADP and increase of collagen in the CLP group, while inhibition in the CLP + UTI group and 3) by HPLC evaluation of adenine nucleotide in the platelet, increased levels of total ATP and ADP in the CLP group, particularly, increases of ATP in the metabolic pool and ADP in the granular pool. CLP + UTI group did not show these changes in the adenylate pool. UTI was thus considered to stabilize the platelet cycle in sepsis. Platelets under septic state might be hyperactive, and thrombosis is easy to occur. UTI administration might work for maintaining constancy of the platelet internal environment and improve septic state because adenine nucleotide level in the platelet did not change in the CLP + UTI group through changed in the CLP group.

Platelets of patients affected with essential thrombocythemia are abnormal in plasma membrane and adenine nucleotide content

The adenine nucleotides present in distinct cellular compartments of platelets of 27 patients affected with essential thrombocythemia have been measured. In order to quantify granule-bound nucleotides and adenylic cytoplasmic pool, platelets have been stimulated with thrombin or treated with increasing digitonin concentrations, respectively. Among patients, we have identified two groups: 12 patients (Group 1) had normal platelet level of ATP and ADP both in dense granules as well as in cytoplasmic pool. The other patients (Group 2) had granule ATP and ADP significantly lower and ATP/ADP ratio significantly higher than controls. In these patients an increase in hypoxanthine level, derived from metabolic ATP degradation occurring during stimulation, was observed. In addition, in the latter patients an increased resistance of plasma membrane to digitonin was shown, suggesting that membrane fluidity should be reduced owing to a modified cholesterol/phospholipid ratio.

Measurement of red blood cell adenosine nucleotides by high-performance liquid chromatography

A new method for measuring ATP in stored red blood cells using high-performance liquid chromatography was compared with an established enzymatic method. The new method is based upon isocratic reverse phase chromatography using a polyvinyl alcohol gel stationary phase. The chromatograms produce quantitative results for ADP, AMP, and other nucleotides, and can be used to determine adenylate energy charge. The correlation coefficient between the two methods was 0.91, and mean ATP was 3.0 mumol/g Hb for both methods. Tests of hypothesis for mean and variance were not significant. The method is recommended as a means to study the relationships between poststorage red blood cell ATP, adenylate energy charge, total adenylates, and posttransfusion erythrocyte survival.

Studies on the pigeon red blood cell metabolism

1. Pigeon erythrocyte was found to depend on the glycolytic and pentose phosphate pathway for most of its energy production in the form of adenosine triphosphate and reducing potential, since there was no detectable activity of any of the citric acid cycle (TCA) cycle enzymes measured. 2. The absence of detectable amounts of 2,3-diphosphoglyceric acid (2-3-DPG) indicated that there is no direct relationship between the active glycolytic system and the function of these cells. 3. A comparison of the mass action ratios with the equilibrium constants of the glycolytic reactions showed that hexokinase, phosphofructokinase and pyruvate kinase reactions are displaced from equilibrium, implying that these are the key regulatory enzymes of glycolysis in pigeon erythrocytes. 4. The changes in the concentrations of the glycolytic metabolites under hypoxic conditions that stimulate the flux through the glycolytic pathway were found to be consistent with the above hypothesis. 5. Flux measurements of the pentose phosphate pathway showed that it metabolizes only 3.4% of the total glucose consumed by the resting erythrocyte. 6. Hypoxic conditions resulted in a stimulation of the pentose phosphate pathway by as much as four-fold, whilst the glycolytic pathway was not stimulated by more than about twice.

High concentrations of 2-5A, the interferon intracellular mediator, in the blood of children with acute viral infections

We measured the concentration of 2-5A (2',5'-oligoadenylate), an intracellular mediator of the antiviral action of interferon, in the blood of children with acute viral and bacterial infectious diseases. 2-5A concentration was found to be elevated in several children with viral diseases. This elevation seemed transient and was not specific for viral infections. We provide arguments for the use of 2-5A as a marker of the evolution of diagnosed viral diseases.

AMP deaminase as a cell-age marker in transient erythroblastopenia of childhood and its role in the adenylate economy of erythrocytes

Erythrocytes from 11 patients with presumptive diagnoses of transient erythroblastopenia of childhood were evaluated retrospectively (six) or prospectively (five) for a possible relationship between erythrocyte adenosine 5'-monophosphate aminohydrolase, adenylic acid deaminase (AMP deaminase) activity and intracellular concentrations of adenine nucleotides. Older red blood cell (RBC) cohorts in these patients consistently exhibited significantly decreased activities of AMP deaminase (approximately 5% to 70% of normal control mean) in association with increased concentrations (up to threefold) of adenosine triphosphate (ATP) and total adenine nucleotides. We postulate that the latter is a direct consequence of the former, since diminishing AMP deaminase activity in aging cells should reduce the drain on the adenine nucleotide pool imposed by irreversible deamination of AMP to inosine 5'-monophosphate. Consistent reductions in AMP deaminase activity indicate that this enzyme should also serve as a reliable marker of mean RBC age useful in diagnostic confirmation of transient erythroblastopenia. The observed increases in ATP and total adenine nucleotides in older RBCs require a reevaluation of the traditional view that age-related losses of these compounds mediate the ultimate demise of senescent erythrocytes. Similar alterations in the balance of degradative and salvage pathways in RBC nucleotide metabolism may also underlie certain cases of so-called "high ATP syndrome."

Evaluation of platelets prepared by apheresis and stored for 5 days. In vitro and in vivo studies

To evaluate the effect of storage on apheresis platelets collected with a closed-system blood cell separator, an in vitro investigation was performed, with measurements of pH, lactate, ATP, the ratio of ATP to the total adenine nucleotide content, and adenylate kinase. Unmodified apheresis platelets and apheresis platelets with plasma added were compared with conventional platelets stored in PL-1240 or PL-732 plastic containers. During 6 days of storage, there were similar changes in all variables with one exception: the extracellular activity of adenylate kinase was lower in apheresis platelets with plasma than in the other three groups (p less than 0.01). In vivo studies were carried out with 111Indium-labeled autologous platelets in eight volunteers. Apheresis platelets with 100 mL of plasma added were stored in two 1000-mL containers (PL-732) at 22 degrees C during agitation. Platelets from one of the containers were labeled with 111Indium and transfused into the volunteer within 24 hours. Platelets from the other container were labeled after 5 days of storage and transfused into the same donor. There were no significant differences between apheresis platelets stored for 1 day and those stored for 5 days: the mean percentage of recovery was 58.4 and 57.6 percent, t1/2 was 69 and 67 hours, and the survival time was 5.5 and 5.6 days, respectively.

Extracellular adenine compounds, red blood cells and haemostasis: facts and hypotheses

Previously, the role of adenine nucleotides was thought to be confined to the intracellular space of the cell. Research of the last decades has revealed that nucleotides also occur in the extracellular milieu. This survey deals with extracellular adenine compounds in the blood, focussing on their role as chemical mediators in the haemostatic effect of red cells. Erythrocytes may act as pro-aggregatory cells by at least two chemical mechanisms. Firstly, they can enhance platelet aggregation by releasing adenosine diphosphate (ADP), a well known platelet stimulatory substance. ADP is set free when red cells are stressed mechanically, for instance by shear forces generated in the blood stream; ample experimental evidence supporting this view is summarized. Secondly, erythrocytes efficiently take up extracellular adenosine via their nucleoside transporters, thereby removing a potent inhibitor of platelet function. Extracellular adenosine occurs in the blood stream, either directly released from various tissues or as the end product of extracellular adenine nucleotide metabolism, e.g. after degradation of red cell-born ADP or ATP. Finally, a novel mechanism of action of the antithrombotic drug dipyridamole, which has very recently been put forward, is demonstrated. Dipyridamole inhibits platelet function indirectly by blocking the uptake of extracellular adenosine via the nucleoside transporter of red cells; increased adenosine levels in turn are responsible for the antiaggregatory effect of dipyridamole.

Metabolism of adenine nucleotides in human blood

Biologically active concentrations of potently vasoactive and platelet-active adenine nucleotides are generated in plasma by a variety of pathophysiological mechanisms. Although there is evidence that ATP and ADP are inactivated by endothelial ectonucleotidases, there has been little attempt to study the metabolic routes of their catabolism in blood or to assess the contribution of this process to their clearance in vivo. Therefore, we have studied the rates and patterns of catabolism of ATP, ADP, and AMP in whole blood, plasma, and isolated blood cells. Rates of degradation of each nucleotide in cell-free plasma ranged from 0.07-0.32 nmol/min/ml with 1 microM substrates to 1.1-3.6 nmol/min/ml with 100 microM substrates. The pattern of catabolism indicated that sequential dephosphorylation from ATP----ADP----AMP----adenosine occurs. In whole blood, the pattern was similar although ATP and ADP (but not AMP) breakdown was more rapid. This was due to leukocyte ectonucleotidase activity. The use of selective inhibitors demonstrated that catabolism was not due to nonspecific phosphatase activity and that plasma 5'-nucleotidase is distinct from ATPase or ADPase. In leukocytes, ATPase and ADPase activities were distinguishable, and each contributed substantially to the rates of catabolism in whole blood. Leukocyte 5'-nucleotidase did not measurably contribute to AMP dephosphorylation in blood. By comparison, ecto-ATPase and ecto-ADPase activities on cultured human umbilical vein endothelial cells were similar to those on leukocytes while endothelial 5'-nucleotidase per 10(6) cells was equivalent to the soluble activity in 1 ml of blood or plasma.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphoenolpyruvate in the rejuvenation of stored red cells in SAGM medium: optimal conditions and the indirect effect of methemoglobin formation

Red cells stored in saline-adenine-glucose-mannitol (SAGM) medium were rejuvenated by incubation with phosphoenolpyruvate (PEP) under conditions that can be achieved easily in ordinary blood banking. Regeneration of 2,3 diphosphoglycerate (2,3 DPG) and adenine nucleotides of stored red cells was dependent on the pH of the incubation medium and the incubation time. In red cells stored for 3 and 5 weeks, the optimal pH and incubation time for regeneration of 2,3 DPG and adenine nucleotides were 5.8 and 90 minutes and 6.1 and 60 minutes, respectively. During the incubation of red cells with PEP, methemoglobin was formed; it increased when the medium pH was below 6.0 and the incubation time exceeded 60 minutes. We conclude that incubation at a medium pH of 6.1 for 60 minutes is optimal for the rejuvenation of stored red cells with PEP. Under such incubation conditions, the concentrations of 2,3 DPG and adenine nucleotides in red cells stored for 5 weeks were restored to normal without methemoglobin formation.

Impaired cytoplasmic ionized calcium mobilization in inherited platelet secretion defects

Defects in platelet cytoplasmic Ca++ mobilization have been postulated but not well demonstrated in patients with inherited platelet secretion defects. We describe studies in a 42-year-old white woman, referred for evaluation of easy bruising, and her 23-year-old son. In both subjects, aggregation and 14C-serotonin secretion responses in platelet-rich plasma (PRP) to adenosine diphosphate (ADP), epinephrine, platelet activating factor (PAF), arachidonic acid (AA), U46619, and ionophore A23187 were markedly impaired. Platelet ADP and adenosine triphosphate (ATP), contents and thromboxane synthesis induced by thrombin and AA were normal. In quin2-loaded platelets, the basal intracellular Ca++ concentration, [Ca++]i, was normal; however, peak [Ca++]i measured in the presence of 1 mmol/L external Ca++ was consistently diminished following activation with ADP (25 mumol/L), PAF (20 mumol/L), collagen (5 micrograms/mL), U46619 (1 mumol/L), and thrombin (0.05 to 0.5 U/mL). In aequorin-loaded platelets, the peak [Ca++]i studied following thrombin (0.05 and 0.5 U/mL) stimulation was diminished. Myosin light chain phosphorylation following thrombin (0.05 to 0.5 U/mL) stimulation was comparable with that in the normal controls, while with ADP (25 mumol/L) it was more strikingly impaired in the propositus. We provide direct evidence that at least in some patients with inherited platelet secretion defects, agonist-induced Ca++ mobilization is impaired. This may be related to defects in phospholipase C activation. These patients provide a unique opportunity to obtain new insights into Ca++ mobilization in platelets.

Decreased erythrocyte phosphoribosylpyrophosphate synthetase activity and impaired formation in thalassemia minor: a mechanism for decreased adenine nucleotide content

Adenosine triphosphate (ATP) and adenosine diphosphate levels are decreased in erythrocytes from individuals with beta-thalassemia minor. Because 5-phosphoribosyl-1-pyrophosphate (PRPP) is an essential precurosr of adenine nucleotides, we tested the hypothesis that impaired PRPP synthesis is a mechanism for the decreased adenine nucleotide content. Erythrocyte PRPP synthetase activity was significantly decreased, and the Michaelis-Menten constant (Km) for ribose-5-phosphate (R5P) was significantly increased in individuals with alpha-thalassemia minor and those with beta-thalassemia minor. Intact erythrocytes from individuals with alpha-thalassemia and those with beta-thalassemia minor also had an impaired rate of PRPP formation. Both the decrease in PRPP synthetase activity and the impaired PRPP formation were also found in erythrocytes with microcytosis resulting from iron deficiency, indicating that these phenomena may not be specific to thalassemia minor. In all individuals examined, the rate of PRPP formation correlated with ATP content, suggesting that either (1) PRPP synthetase activity is a determinant of ATP content or (2) ATP content is a determinant of PRPP synthetase activity. The depletion of ATP from normal erythrocytes did not affect PRPP synthetase activity, suggesting that ATP content is not a determinant of PRPP synthetase activity. However, a decrease in PRPP synthetase activity did cause an impairment in the rate of adenine nucleotide synthesis, suggesting that PRPP synthetase activity is a determinant of ATP content. Taken together, our results suggest that the decrease in PRPP synthetase activity and the resulting impairment in the rate of PRPP formation are mechanisms for the decreased adenine nucleotide content in thalassemic erythrocytes.

Maturation-dependent changes of the rabbit reticulocyte energy metabolism

Rabbit reticulocytes were separated into four fractions of different maturity in order to investigate the changes of cellular respiration and glycolysis, adenine nucleotides, 2,3-biphosphoglycerate (2,3-BPG) as well as cyclic AMP level during the transition from the youngest to the most mature reticulocytes. A significant reduction of total oxygen consumption, mainly due to depression of coupled respiration was found. The decline of respiration was accompanied by a 2-fold increase of the rate of aerobic glycolysis indicating a reduced Pasteur effect during maturation. A decline of ATP and an increase of ADP concentration was found. The oxygen-delivery capacity of the red cells increased by about 26% caused by an increase of the 2,3-BPG level of about 2 mmol/l cells. Cyclic AMP level in the fraction of youngest reticulocytes was about 60-fold higher than that in mature rabbit erythrocytes. The biggest decline of cyclic AMP was registered during the transition from youngest to the intermediate stage of maturity.

Permeabilization of platelets: an investigation of biochemical, ultrastructural and functional aspects

The biochemical, ultrastructural and functional aspects of digitonin-permeabilized platelets were investigated. Human platelets were permeabilized by exposure to the steroid glycoside digitonin. A 60 microM concentration of this permeabilizer produced a very substantial release of cytosolic enzymes from the platelets. Release from subcellular granules was relatively low and did not inhibit the response of platelets to a series of agonists. Although digitonin-permeabilized platelets required higher threshold concentrations of the usual stimulants, both primary and secondary aggregation as well as the release of nucleotides and enzymes from their respective granules remained intact. Transmission electron micrographs revealed discontinuities in the plasma membrane of digitonin-treated platelets, but scanning electron microscopy showed no difference between control and permeabilized platelets. No substantial loss of structural or membrane proteins could be detected by one- and two-dimensional gel electrophoresis. The pore size produced by digitonin treatment was sufficient to allow entry of 125I-labeled IgG into the platelet cytosolic space.

Reversible electropermeabilisation of human and rat blood platelets: evaluation of morphological and functional integrity 'in vitro' and 'in vivo'

A high-voltage discharge procedure has been developed for permeabilising the plasma membranes of both human and rat blood platelets. The cells can be resealed by incubation at 37 degrees C, show less than 4% loss of lactate dehydrogenase (LDH) implying minimal cell lysis and also have well maintained morphological and functional integrity. The prototype apparatus used at field strengths between 6 and 8 kV/cm produces membrane pores which allow free diffusion of low molecular weight substances such as adenine nucleotides, inositol phosphate and fluorescent dyes. Two properties, namely Ca2+-induced secretion of granule stored 5-hydroxytryptamine (5HT) and inositol 1,4,5-trisphosphate (IP3)-induced release of intracellularly sequestered 45Ca, which are both well expressed immediately after permeabilisation, are essentially abolished after resealing. The efficiency of permeabilisation and resealing can be simply monitored by shifts in 'apparent platelet volume' using a resistive particle counter (Coulter). Permeabilised platelets show a shift in modal volumes from a control range 4-7 fl to 10-15 fl. Resealing restores these modal volumes to the original control range. Encapsulation of the fluorochrome, Lucifer yellow (Mr 550), during permeabilisation revealed that after resealing greater than 85% of rat platelets, and close to 100% human platelets, contained the encapsulated dye. The initial rates and % aggregation responses of both human and rat platelets to collagen, thrombin and the thromboxane A2-mimetic U46619 remained essentially normal after permeabilisation and resealing further illustrating the maintenance of functional competence following treatment. Resealed rat platelets reinfused into the circulation after labelling with [111In]indium oxine gave survival curves similar to those of control platelets. Therefore, this reversible permeabilisation procedure may allow the use of autologous or heterologous platelets as carrier vehicles for the delivery of drugs and other agents 'in vivo'.

[Experimental studies on influences of intermittent hemihepatic vascular occlusion]

The influences of intermittent hemihepatic vascular occlusion in rats were investigated. The restoration of tissue energy level during 10 min of reperfusion after more than 40 min of occlusion was significantly lower than after occlusion within 30 min. over 40 min of occlusion which resulted in a significant increase of tissue free fatty acids during occlusion showed marked decrease of total adenine nucleotides (TAN) in the liver and marked increase of serum TAN in the hepatic vein after reperfusion. It was presumed that these findings were caused by wash-out of adenine-nucleotides from liver cell to the hepatic vein after reperfusion correlated with degradation of cell membrane. Thus, less than 30 min of occlusion was safe in hemihepatic vascular occlusion. Three times intermittent occlusion--repeats of 30 min of occlusion and 10 min of reperfusion--resulted in a same tissue energy level as once 40 min of occlusion. Furthermore, there was no difference in serum ornithine carbamoyltransferase, tissue oxygen consumption and ICG test during 48 hrs after reperfusion between three times intermittent occlusion and once 40 min of occlusion. These findings indicated that repetition of short time occlusion was useful in order to safely prolong total ischemic time in hemihepatic vascular occlusion.