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PubMed1996

Hormonal stimulation of calcium mobilization in the isolated perfused rat pancreas.

Hormone-stimulated cellular Ca2+ mobilization in the isolated perfused rat pancreas was investigated by analyzing the efflux profiles of 45Ca2+ from 45Ca(2+)-loaded pancreata following agonist stimulation. The increased 45Ca2+ efflux reflects the enhanced exchange of Ca2+ across the plasma membrane as a result of increased [Ca2+]i. Both high and low concentrations of the cholecystokinin analog, cerulein, applied to the isolated perfused pancreas gave rise to an increased release of 45Ca3+. The patterns of the increase in 45Ca2+ release were consistently different for high and low concentrations of the agonist. Cerulein infused at a concentration of 10(-11) M induced a release of a small but significant amount of 45Ca2+ which could be abolished by 8-(N,N-diethylamine)octyl-3,4,5-trimethoxy-benzoate (TMB-8), but was not affected by ethyleneglycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA). Cerulein stimulation at 10(-9) M elicited a marked increase in 45Ca2+ release which was minimized by EGTA, but not by TMB-8. Also, infusion of cerulein stimulated a concentration-dependent amylase secretion response which displayed the same TMB-8- and EGTA-sensitivity pattern as the 45Ca2+ release response. The present study suggests (i) that cellular Ca2+ influx is a prominent feature of the increased 45Ca2+ efflux (i.e., increased [Ca2+]i) induced by pharmacological concentrations of cerulein while physiological concentrations of cerulein cause an increase in [Ca2+]i which is due predominantly to a release of internal Ca2+; and (ii) [Ca2+]i changes are essential for pancreatic enzyme secretion. Although isolated pancreatic acini or cells may lose their sensitivity and physiological responses to various agonists during isolation and preparation, the isolated perfused pancreas is a suitable and very sensitive model in which to study the physiology of Ca2+ mobilization and enzyme secretion.

Amylases↗
PubMed1980

Uptake of 5-fluorouracil during isolated perfusion of the canine liver.

This study describes a technique of hepatic isolated perfusion in dogs. The uptake of 14C-labeled 5 fluorouracil (5-FU) by the normal canine liver was fourfold greater when isolated perfusion was used than when peripheral intravenous administration or hepatic artery infusion were applied. Systemic leakage of 5-FU was small during, and even following, hepatic isolated perfusion. This technique, which maximizes chemotherapy delivery to the liver while minimizing systemic toxicity, may be useful in the treatment of primary and metastatic hepatic malignancies.

Animals↗
PubMed1988

Leukotriene C4 action and metabolism in the isolated perfused bullfrog heart.

The effects of leukotrienes (LTs) have been widely studied in the isolated perfused mammalian heart; however, little is known about the effect or metabolism of LTs in the isolated bullfrog heart. Isolated perfused bullfrog hearts were administered randomized doses of LTC4, LTD4, or LTE4. The cardiac parameters of heart rate, developed tension, and its first derivative (dT/dt) were recorded. LTC4 was the most potent of the leukotrienes tested in eliciting positive inotropic effects. LTD4 and LTE4 were equally effective but about one order of magnitude less potent than LTC4. None of the LTs showed any chronotropic effects in this preparation. A series of [3H]LTC4 metabolism experiments were carried out using whole perfused hearts and minced bullfrog heart tissue. Isolated perfused bullfrog hearts administered [3H]LTC4 converted significant amounts to [3H]LTD4, and to a lesser degree, [3H]LTE4, during the 6-min course of collection. Both minced atrial and ventricular tissue converted [3H]LTC4 to radioactive metabolites that co-migrated with authentic LTD4 and LTE4 standards. In both tissues, the major product was [3H]LTD4, with smaller amounts of [3H]LTE4 produced. The atrium converted significantly more [3H]LTC4 to its metabolites than did the ventricle. The metabolism of [3H]LTC4 to [3H]LTD4 by both tissues was virtually abolished in the presence of serine borate. Cysteine had no effect on [3H]LTE4 production. The data in this study demonstrate that leukotrienes have the opposite inotropic effect on the heart when compared with mammals. Also in contrast to mammals, frogs metabolize LTC4 to a less potent compound and may use the LTC4 to LTD4 conversion as a mechanism of LTC4 inactivation.

Animals↗
PubMedDate not supplied

Modification of human tumour and normal tissue pH during hyperthermic and normothermic antiblastic regional isolation perfusion for malignant melanoma: a pilot study.

Human tumour and normal tissue pH were investigated during hyperthermic and normothermic antiblastic regional isolation perfusion and the effects of vascular occlusion, artificially induced hypoxia, hyperglycaemia, haemoglobin level of the perfusate and hyperthermia on tumour and normal tissue pH were evaluated. A pilot study was performed on 10 patients, with locally inoperable recurrent and primary malignant melanoma of the leg. The treatment consisted of a regional isolation perfusion with hyperthermia (120 min at 42-43 degrees C), at femoral level, followed by a normothermic regional isolation perfusion with Melphalan (60 min at 37-38 degrees C), at iliacal level, 7-10 can be distinguished: (1) first ischaemic anoxia period; (2) extracorporeal circulation, during which the leg is heated to the desired temperature, after which either hyperthermia or Melphalan is applied; (3) second ischaemic anoxia period. During the anoxia periods the large vessels that supply the leg are temporarily clamped and the effects on tissue pH can be investigated. During extracorporeal circulation, high-dose glucose can be administered to the isolated leg, to acutely decrease tumour tissue pH. Such a decrease is expected to sensitize tumours to hyperthermia, when applied immediately prior to or during heating. At the beginning of the treatment the mean tumour pH was significantly lower than normal tissue pH (7.14, with a mean tumour volume of 39.2 cm3, and 7.38, respectively; p < 0.01). During the perfusions with hyperthermia and Melphalan, tissue pH decreased by -0.41 units and -0.20 for tumour, and -0.11 units for normal tissue, respectively (all statistically significant). The two anoxia periods accounted for approximately half of the net decrease. During these periods tumour pH appeared to decrease more selectively, although there was great variation. The other investigated modalities, such as hyperglycaemia and hyperthermia, also decreased tissue pH, but to a lesser extent. However, a combination of more than one modality caused a larger decrease than a single one, but no preference for tumour could be detected. Before the second perfusion mean tumour pH was significantly increased by 0.14 units, and was no longer significantly different from normal tissue pH in the course of the regional isolation perfusion. This could be the reflection of the reduced tumour volume (by 30%, n.s.). Similar pH changes occurred during this Melphalan perfusion, but they were less pronounced since the total treatment time was shorter. Summarizing, tumour pH can be decreased more than normal tissue pH in the course of the regional isolation perfusion. In particular, vascular occlusion appeared to be tumour pH selective.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1972

The conversion of orotic acid into uridine 5'-monophosphate by isolated perfused normal and regenerating rat livers.

The release of (14)CO(2) from [7-(14)C]orotic acid was measured in isolated perfused normal and regenerating rat livers. With some limitations, the release of (14)CO(2) from [7-(14)C]orotic acid can be used to estimate UMP synthesis in perfused livers. Isolated perfused livers rapidly pick up labelled orotic acid added to perfusate and convert most of it into UMP. Perfused regenerating livers produce approx. 2.5 times as much UMP/g of liver as do perfused normal livers. However, the absolute amount of orotic acid converted into UMP is higher in perfused normal livers than in perfused regenerating livers. Perfused regenerating livers do not differ in their orotic acid uptake and UMP synthesis from livers of comparable size in which regeneration is not taking place. The total amount of orotic acid taken up by the liver (rather than the rate of uptake) and the size of the liver appear to be the determining factors in UMP production. The results suggest that the decrease in liver size caused by partial hepatectomy may be in itself sufficient to account for an increase in the flow of metabolites in the pyrimidine pathway at the early stages of liver regeneration.

Animals↗
PubMed2002

The isolated perfused bovine uterus as a model for mucous membrane irritation and inflammation.

Isolated perfused bovine uteri were used to study the irritation potential of antiseptics frequently used in veterinary practice for the treatment of endometritis. Comparable to the isolated perfused bovine udder (Kietzmann et al., 1993), the viability of uteri obtained directly after slaughtering of cows, was tested with the help of biochemical parameters. These parameters of the viability were nearly unchanged over five hours. Thereafter, different antiseptics were tested for their irritation potential on the mucous membrane with the help of the MTT-assay. Here the irritant effect of Lugol's iodine solution is demonstrated exemplarily. An additional study was performed to establish a hemoperfused uterus. An injection of arachidonic acid into the serosa induces a visible inflammatory reaction and a marked increase of the prostaglandin E2 synthesis. In conclusion, the isolated perfused bovine uterus seems to be a promising in vitro model for mucous membrane irritancy as well as for inflammatory reactions.

Animals↗
PubMed1980

Influence of raising albumin concentration on renin release in isolated perfused rat kidneys.

1. Experiments were conducted in isolated perfused rat kidneys to determine the effect of raising perfusate albumin concentration on renin release.2. Raising albumin concentration in the perfusion fluid from 20 g/l. to 60 g/l. (high albumin concentration) increased renin release and renal perfusate flow rate. The effect was reversible.3. Ureteral occlusion did not prevent the rise in renin release and renal perfusate flow induced by high albumin concentration.4. Propranolol (0.28 mM) did not block the renin release stimulated by high albumin concentration, but it inhibited the release stimulated by isoprenaline (2.43 muM).5. Clonidine (10 muM) and oxymetazoline (10 muM) constricted the renal vasculature and stimulated renin release during high perfusate albumin concentration providing perfusion pressure was kept constant.6. Low renal perfusion pressure (50 mmHg) and isoprenaline (2.43 muM) stimulated renin release in perfusion experiments with both 20 and 60 g/l., but the rate of renin release was substantially greater with 60 g/l.7. On the other hand, perfusion fluid deprived of calcium induced a greater increase in renin release in kidneys perfused with 20 g/l. than in those with 60 g/l.8. We conclude that high albumin concentration stimulates renin release in isolated perfused rat kidneys by a mechanism which does not involve the renal nerve, direct renal vasodilation or sodium excretion. High albumin concentration may increase the sensitivity of the kidney to acute stimulation by a mechanism involving calcium.

Animals↗
PubMed1988

Matrix deposition and extracellular processing of newly synthesized collagens in the isolated perfused rat lung.

We have examined the matrix deposition and proteolytic processing of newly synthesized interstitial and basement membrane collagens in the isolated perfused adult rat lung. Isolated, perfused, and ventilated lungs were labeled for up to 4 h with radiolabeled proline. Collagens were partially purified from homogenates by salt fractionation and ion exchange chromatography and examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The major collagenous species were identified as types I, III, and IV collagen by peptide mapping and indirect immunoprecipitation assays. Whereas extraction with neutral salts recovered radiolabeled types I and III collagen, extraction of the neutral salt residue with 2 M guanidine-HCl preferentially recovered types III and IV collagen. Reextraction of the guanidine-HCl residue in the presence of dithiothreitol selectively recovered type IV procollagen (PC) and covalently cross-linked aggregates of type IV chains. In pulse-chase experiments we observed extensive conversion of type I PC to collagen during a 4-h chase. Although type III PC was efficiently converted to p-collagen, only small amounts of fully processed chains were identified. Type IV PC did not undergo detectable proteolytic processing. The isolated perfused rat lung should prove useful for further studies of lung collagen metabolism.

Animals↗
PubMed1986

The release of intralysosomally-stored 125I-Triton WR-1339 and lysosomal enzymes from the isolated perfused rat liver in the presence and absence of cytochalasin B.

The effect of in vivo loading of the lysosomotropic agent 125I-Triton WR-1339 on the release of lysosomal enzymes in isolated perfused rat liver has been studied in the presence and absence of the microfilament poison cytochalasin B, as has the release of the 125I-Triton WR-1339 itself. Perfused isolated rat livers released all the enzymes studied (arylsulphatase, beta-galactosidase and lactate dehydrogenase) and, when preloaded, 125I-Triton WR-1339 was also released into the perfusate. The magnitude of the net release (after 5 hr perfusion) was in the order beta-galactosidase = 125I-Triton WR-1339 greater than lactate dehydrogenase greater than arylsulphatase. Preloading of the lysosomes with the detergent appeared to bring about an increase in the release of all the enzymes studied (3.5 X for beta-galactosidase, 2.6 X for arylsulphatase and 1.7 X for lactate dehydrogenase). The addition of the microfilament poison cytochalasin B into the perfusate of non-loaded livers significantly increased the release of the lysosomal enzymes but not that of lactate dehydrogenase. However in the 125I-Triton WR-1339- loaded livers cytochalasin B had no effect on the release of lysosomal enzymes or detergent, but reduced the loss of lactate dehydrogenase by about 50%. This failure of cytochalasin B to potentiate the exocytosis of lysosomal contents in 125I-Triton WR-1339-loaded livers is similar to the effect found previously with 125I-PVP-loaded livers and may be related to the already enhanced loss of lysosomal enzymes apparently caused by the loading.

Animals↗
PubMed1991

The isolated perfused human skin flap: design, perfusion technique, metabolism, and vascular reactivity.

The design, isolated perfusion technique, and reactivity of a novel human skin-flap model are described. A transverse paraumbilical skin flap based on perforator vessels from the deep epigastric system was designed utilizing the tissue usually discarded following abdominal dermolipectomy. Within 3 hours of devascularization, a gassed (95% O2, 5% CO2), 37 degrees C Krebs-Henseleit buffer containing albumin (65 gm/liter) was pumped into the cannulated arterial pedicle of the skin flap and subsequently collected from the venous pedicle. Vascular resistance was continuously monitored and remained stable throughout the 4-hour perfusion. Lactate release was maintained throughout perfusion and was markedly increased by addition of insulin to the perfusate. Addition of norepinephrine to the perfusate resulted in a significant (p less than 0.05) dose-response increase in vascular resistance, and acetylcholine significantly (p less than 0.05) attenuated resistance in flaps preconstricted with norepinephrine. The results of these studies indicate that the isolated perfused human skin flap remained metabolically active with functionally intact vascular endothelium and smooth muscle throughout the 4-hour perfusion. The availability of this technique will, for the first time, permit laboratory study of human skin-flap pathophysiology and pharmacology.

Animals↗
PubMed1986

[In vitro and in vivo effect of gold thioglucose on the insulin- and glucagon-secretion of the isolated perfused rat pancreas].

Effects of gold thioglucose on the insulin and glucagon secretion by the isolated perfused pancreas of Wistar rats in vivo and in vitro Gold thioglucose (GTG), hitherto administered predominantly to mice can also be used in rats in a non toxic dosage, if GTG is injected intravenously (i.v.) together with sodium hexobarbital. Wistar rats tolerate a single injection of GTG in doses ranging from 40 to 1200 mg/kg bw. GTG (10 mmol/l in the perfusion medium) has no in vitro effect--tested by the isolated perfused rat pancreas--on the basal (5.5 mmol/l glucose) or stimulated (11 mmol/l glucose) insulin (IRI)-secretion. This is valid also for glucagon (IRG)-secretion. After in vivo injection of GTG (600 mg/kg bw, together with sodium hexobarbital (10 mg/100 g bw, i.v.] extensive alterations of IRI- and IRG-secretion result as tested under in vitro conditions in the isolated perfused pancreas of the rat, Glucose stimulation (11 mmol/l) causes a hyperinsulinism and a hypersecretion of IRG, a so-called paradoxical glucagon secretion, lasting for 2 days while IRI secretion is already diminished. At the same time food intake is very low and the body weight decreases. Ten days later the body weight has reached the starting value again and the IRI secretion shows again signs of hyperinsulinism. Six months after a single injection of GTG (600 mg/kg bw, i.v.) the rats were obese and react after glucose stimulation with hyperinsulinism and again with a paradoxical glucagon secretion. The blood glucose levels were normoglycaemic, whereas serum IRI rose in parallel with development of the obesity. Also with histological methods we could distinguish an acute from a chronic phase of GTG toxicity visible in the tested organs (liver, kidney, thyroid gland). The endocrine pancreas reacts after a single injection of GTG with a lowered number of B cells. The remaining cells reveal variable amounts of degranulation. In the early phase the hypothalamus, in particular the ventromedial hypothalamic nucleus, shows most clearly signs of destruction and 6 months after a single injection of GTG the number of cells is still reduced in this region. We conclude that GTG reacts primarily on the hypothalamus and modulates the reactivity of the endocrine pancreas in a permanent manner via the vegetative nervous system, because we test the function of the pancreas in an in vitro system. As a consequence the threshold of the B and A cell against the stimulus glucose is altered in two ways.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1978

Autoregulation of plasma flow in the isolated perfused rat kidney.

1. Autoregulation of renal plasma flow, by which flow remains constant despite changes in perfusion pressure, was studied in the isolated, perfused kidney of the rat. 2. Autoregulation did not occur in preparations perfused with a protein-free medium consisting of a balanced ionic solution resembling rat plasma in which 3% polyvinylpyrrolidone replaced the plasma proteins, changes in perfusion pressure over the normal autoregulatory range 100-150 mmHg produced a corresponding and linear change in venous outflow and no consistent change in renal vascular resistance. 3. Addition of human serum (5%, v/v) to the medium restored autoregulation; changes in perfusion pressure in the range 100-150 mmHg resulted in a stable plasma flow and a linear change in renal vascular resistance. The addition of bovine serum albumin (3 g/1.) to the protein-free medium restored autoregulation to a similar degree. 4. In kidneys perfused with the protein-free medium, the sensitivity of the renal vasculature to the vasoconstrictor drugs epinephrine and angiotensin II was only 1/40 the level seen in those kidneys perfused with media containing serum or albumin. 5. The experiments show that in the isolated, perfused kidney, autoregulation of plasma flow is not dependent on the presence of the globulin, angiotensinogen, in the perfusion medium; and suggest that failure of autoregulation in kidneys perfused with a protein-free medium could be attributed to the rapid decline in the sensitivity of the vascular smooth muscle to constrictor stimuli.

Angiotensin II↗
PubMed1991

Toxicity and kinetics of [3H]microcystin-LR in isolated perfused rat livers.

Isolated rat livers were perfused for 60 min with either 0.3 or 0.5 microgram/ml (initial volume, 119 ml) of [3H]microcystin-LR at a constant flow of 10 ml/min in a recirculating system. During the 60-min exposure, toxin caused stimulation of glycogenolysis, liver engorgement, and cessation of bile flow. Electron micrographs of liver showed dilation of bile canaliculi and the space of Disse. loss of sinusoidal lining architecture, and decreased hepatocyte intercellular contacts. Although hepatocytes did not exhibit overt necrosis, mitochondria were hydropic, occasionally encircled by whorls of rough endoplasmic reticulum, and desmosomal tonofilaments were decreased on the plasma membrane lateral surface. Isolated mitochondria displayed inhibition of state 3 respiration and a 50-60% decrease in the respiratory control index, characteristic of hydropism. Distribution of radiolabel was 1.7% to bile, 79% to perfusate, and 16% to liver. Two to four percent was recovered in perfusate that leaked from the surface of the liver. Of the radiolabel found in bile and perfusate, 78 and 100% were associated with parent toxin, respectively. The radiolabel in liver, associated with the cytosolic fraction (S-100), corresponded to parent toxin (15%) and to a more-polar component(s) (85%). The elimination half-life from perfusate was 130 +/- 10 min (0.5 microgram/ml) and the hepatic extraction ratio 0.07 +/- 0.01. Although the calculated hepatic extraction ratio was low, there was a significant accumulation of microcystin in the liver. Many toxic effects of microcystin in the perfused liver mimicked those observed in the whole animal, suggesting that this model can be used as an alternative to whole animals for screening of potential therapeutic agents.

Animals↗
PubMed1994

Influence of perfusion flow rate on uptake and pharmacodynamics of quinidine in isolated perfused rat heart.

With the single-pass isolated perfused rat heart preparation, we examined the effect of perfusate flow rate on the time course of quinidine output concentration (Cout) and the change in the QT interval (delta QT) on the electrocardiogram. Four hearts were perfused at 5.6 mL/min with quinidine (20 microM) for 25-45 min. This was followed by a 50-min washout period with drug-free perfusate. This procedure was repeated four times in each heart. Using a one-compartment model, the rate constants calculated from the time course of Cout (k) and delta QT (Ke) were similar (p > 0.05) and did not vary among the five phases. A zero-time intercept for Cout indicated shunting of perfusate (1.2-13.6%), from which the coronary output concentration (Ccor) and coronary flow rate were calculated. These experiments were repeated in another six hearts, except flow rates of 2, 4, 6, 8, and 2 mL/min were used in each phase. Equilibration of Cout and delta QT was faster with increasing flow rate, and ke and k were similar at each flow rate (p > 0.05). A modified Kety-Renkin-Crone equation was fitted to values for k and coronary flow rate. The mean permeability surface product estimate was 15.3 +/- 3.0 mL/min/g heart, which in comparison with the highest flow rate used (9 mL/min/g heart) suggests that quinidine has intermediate permeability. The excellent fit obtained indicates that a more complex model, incorporating heterogeneous flows or opening of capillaries at higher flows, was not necessary.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1980

Kinetics of uptake and biliary excretion of benzo(alpha)pyrene and mutagenic metabolites in isolated perfused rat liver.

An isolated liver perfusion system was used as a simplifying tool to study the metabolism and excretion of benzo(alpha)pyrene (BP) as a prototype carcinogen/mutagen. Phenobarbital (PB) was used to induce liver microsomal enzymes in Sprague-Dawley male rats prior to isolated liver perfusion. Control livers were run simultaneously using generally tritiated (G-3H)BP/BP as substrate in the perfusion medium. Both biliary excretion and liver weight were increased in the induced compared to control liver, but biliary flow when corrected for liver weight is statistically the same for both control and PB-induced livers. The excretion rat of radioactivity in the bile is always higher for PB-induced than for control liver (maximum radioactive excretion at 1 hr). There is a more rapid radioactivity removal in the liver perfusion medium for PB-induced than for control livers. Data are explained by increased metabolism of BP in induced liver leading to the presence of more polar metabolites undergoing preferential biliary excretion than in the control liver. Results support in vivo experimental data. Extracts from liver and bile were tested for microbial mutagenicity by the Ames test (TA 100) after TLC separation. The control liver shows virtually no mutagenicity in bile, only in TLC fractions from the liver. The PB-induced liver shows significant mutagenicity in several TLC fractions in both bile and liver. The net effect of induction is to produce more mutagenic metabolites of BP, excreted in the bile, and presenting a significant exposure of carcinogens/mutagens, and consequent hazard to man.

Animals↗
PubMed1981

Endotoxin protects against chlorpromazine-induced cholestasis in the isolated perfused rat liver.

Induction of endotoxin tolerance or acute chlorpromazine treatment caused a decrease in bile and perfusate flow in the isolated perfused rat liver. The primary effects of each appeared to be on the bile acid-independent fraction of bile. Both the induction of endotoxin tolerance and the in vitro treatment of the perfused rat liver with endotoxin partially blocked the adverse effects of chlorpromazine on bile formation and perfusate flow. Although the "protective" effects of the in vitro endotoxin treatment were dose-dependent, the protection afforded by endotoxin tolerance was greater. Preincubation of isolated hepatocytes with endotoxin, before the addition of chlorpromazine, caused dose-dependent reductions in the chlorpromazine-induced release of aspartate transaminase. However, neither the incubation of endotoxin with chlorpromazine, before addition of membranes isolated from control rats, nor isolation of membranes from endotoxin-tolerant rats affected the inhibitory effects of chlorpromazine on sodium, potassium-, or magnesium-activated adenosine triphosphatase. If endotoxin exerts its protective effects at the membrane level, these data suggest that endotoxin is able to protect the intact, but not the isolated, hepatocyte membrane or that inhibition of adenosine triphosphatases by chlorpromazine is not important in the adverse effects of chlorpromazine on the perfused rat liver and isolated rat hepatocytes.

Animals↗
PubMed2004

Hepatic disposition of cyclosporine A in isolated perfused rat livers.

PURPOSE: To develop an isolated perfused rat liver model to study the hepatic disposition of cyclosporine A (CyA) in both sexes. METHODS: Livers were isolated from male (n = 6) and female (n = 7) rats and perfused with a physiological buffer in a single-pass manner. A bolus 1-mg dose of CyA was injected into the inlet catheter and periodical samples (0-15 min) were collected from the outlet perfusate. The concentrations of CyA in the outlet perfusate, collected bile (0-15 min), and liver tissue (at the end of perfusion) were quantitated by HPLC and subjected to statistical moment analysis. RESULTS: The dilution curves of CyA in the outlet perfusate exhibited unusually long terminal phases due to large volume of distribution of the drug (approximately 100 mL/g) and its slow release from binding sites in the liver (net release rate constant of approximately 0.020 min(-1)). This was in contrast to the rapid uptake of the drug, indicated by significant amounts of the intact drug (>40%) taken up during one single pass through the liver. Consequently, the liver tissue:perfusate distribution ratio of CyA was very high (approximately 220). No significant differences were found between the male and female livers in any of the estimated parameters. CONCLUSIONS: The tissue binding of cyclosporine A is substantial, slowly reversible, and gender-independent in isolated perfused rat livers.

Animals↗
PubMed1976

Nephron function of the isolated perfused rat kidney.

Nephron functions of an improved isolated perfused rat kidney preparation were studied by micropuncture techniques. Single-nephron glomerular filtration rate (SNGFR), intratubular pydrostatic pressures (IP), transit time (TT), and the reabsorption (R) of H2O, Na, Cl, and K were measured in superficial proximal (PT) and distal tubules (DT) of the preparation. Mean SNGFR was 27.2 nl/min and 25.2 nl/min when measured in PT and DT, respectively. The PT transport functions were well maintained throughout the perfusion (mean values were: IP, 14.3 mmHg; TT, 17.7 s; fractional (F) RH2O, 64%; absolute RH2O, 15.4 nl/min; FRNA, 66.5%; FRK, 71%, and tubular fluid-to-perfusate tf/p) ratio of Cl, 1.37). The short loops of Henle reabsorbed less than 10% of the load of H2O and Na delivered to them and the TF/P ratio of electrolytes in the earliest DT segments were high (TF/P)Na = 0.88, (TF/P)Cl = 1.27, and (TF/P)K = 1.11). This deficiency in function of Henle's loop explains, at least in part, the degree of natriuresis of the preparation (overall FRNa = 97.5%). Transit time to end DT was prolonged (82.3 S) and IP in DT elevated (14.9 mmHg). The DT was able to compensate, in part, for the overload from Henle's loop by reabsorbing 36% of the fluid load and 54% of the Na load delivery to it. We concluded that the improved isolated perfused rat kidney is a suitable preparation with which to study several aspects of renal function, particularly proximal tubules transport functions.

Animals↗