Selective estrogen receptor modulator idoxifene inhibits smooth muscle cell proliferation, enhances reendothelialization, and inhibits neointimal formation in vivo after vascular injury.

BACKGROUND: Idoxifene (ID) is a tissue-selective estrogen receptor modulator (SERM). The pharmacological profile of ID in animal studies suggests that it behaves like an estrogen receptor (ER) agonist in bone and lipid metabolism while having negligible ER activity on the reproductive system. It is unknown whether ID retains the vascular protective effects of estrogen. METHODS AND RESULTS: In cultured vascular smooth muscle cells (VSMCs), ID inhibited platelet-derived growth factor-induced DNA synthesis and mitogenesis with IC(50) values of 20.4 and 27.5 nmol/L, respectively. Treatment with ID resulted in S-phase cell cycle arrest in serum-stimulated VSMCs. ID 1 to 100 nmol/L significantly protected endothelial cells from tumor necrosis factor-alpha (TNF-alpha)-induced apoptosis in vitro. Virgin Sprague-Dawley rats ovariectomized 1 week before the study were treated with ID (1 mg x kg(-1) x d(-1)) or vehicle by gavage for 3 days before balloon denudation in carotid artery. The SMC proliferation in injured vessels was determined by immunostaining for proliferating cell nuclear antigen (PCNA). The number of PCNA-positive SMCs was reduced by 69%, 82%, and 86% in the media at days 1, 3 and 7, respectively, and by 78% in the neointima at day 7 after injury in ID- versus vehicle-treated group (P:<0.01). ID significantly enhanced reendothelialization in the injured carotid arteries as determined by Evans blue stain and immunohistochemical analysis for von Willebrand factor. In the former assay, the reendothelialized area in injured vessels was 43% in ID-treated group versus 24% in the vehicle group (P:<0.05); in the latter assay, the numbers of von Willebrand factor-positive cells per cross section increased from 24. 8 (vehicle) to 60.5 (ID) (P:<0.01) at day 14 after injury. In addition, the production of nitric oxide from excised carotid arteries was significantly higher in ID-treated than the vehicle group (8.5 versus 2.7 nmol/g, P:<0.01). Finally, ID treatment reduced neointimal area and the ratio of intima to media by 45% and 40%, respectively (P:<0.01), at day 14 after balloon angioplasty. CONCLUSIONS: The results indicate that ID beneficially modulates the balloon denudation-induced vascular injury response. Inhibition of VSMC proliferation and acceleration of endothelial recovery likely mediate this protective effect of ID.

Evaluation of plasma von Willebrand factor as a biomarker for acute arterial damage in rats.

Plasma von Willebrand factor (vWF) was evaluated as a potential biomarker of acute arterial damage in rats after a vasotoxic dose of the dopaminergic vasodilator, fenoldopam (FP). Male Sprague-Dawley rats were given FP or isotonic saline by subcutaneous injection, and plasma vWF was measured at 2, 6, and 24 hours after challenge. Mean plasma vWF values increased in FP-treated rats compared to controls at 2 hours (167 vs 122%; p < 0.05) and 6 hours postdose (172 vs 130%; p < 0.01) but were comparable to control values after 24 hours. Mesenteric arterial lesions were observed microscopically in all FP-treated rats 24 hours postdose but were not present in rats at 1, 2, 4, 6, or 8 hours after FP challenge. Further, plasma vWF concentrations increased in saline-treated rats after only the minimal perturbation of repeated venipuncture. These results indicate an early, minimal, and transient release of vWF that precedes the onset of morphologically evident vascular damage. The minimal increases in plasma vWF concentrations were of limited predictive value, may be more reflective of an acute-phase reactant response, and were not considered a reliable biomarker of acute FP-induced arterial damage in the rat.

Flow cytometry in the preclinical development of biopharmaceuticals.

Novel biomarkers are often required in the preclinical development of biopharmaceuticals in order to characterize pharmacologic and toxicologic effects and to establish pharmacodynamic and pharmacokinetic relationships. Flow cytometry is uniquely suited for measurement of these biomarkers. Large numbers of single cells in a heterogeneous population can be rapidly identified and characterized with high accuracy and reproducibility. Cells are not damaged by the detection system and can be subsequently sorted for further morphologic or functional analysis. The availability of clinical instruments and a wide range of fluorescent probes have made this technology applicable for use in toxicologic clinical pathology. Flow cytometry has played an integral role in the development of a monoclonal antibody to human CD4 (keliximab, IDEC-CE9.1, SB 210396). Lymphocyte subset analysis and assays for expression, coating, and modulation of human CD4 were used for sequential assessment of the pharmacologic activity of keliximab in transgenic mice expressing human CD4.

A novel method for chronic measurement of pleural pressure in conscious rats.

Pleural pressures are used to evaluate lung function and are generally measured acutely in anesthetized animals. Previous attempts to measure pleural pressure chronically in conscious animals have involved surgical implantation of pressure-sensitive catheters directly into the pleural cavity. The success of these techniques has been limited by lung damage and/or tissue growth and encapsulation of the pressure-sensitive catheter with damping or loss of the signal. These problems have been eliminated by developing a novel surgical procedure for placement of a pressure-sensitive catheter beneath the pleural surface. The catheter (attached to a radiotelemetry transmitter) is surgically implanted beneath the serosal layer of the esophagus within the thoracic cavity. This is accomplished by making a small incision in the serosal layer of the esophagus caudal to the diaphragm and advancing the catheter cranially into the thoracic cavity until pressure changes are maximal. The accuracy of these measurements was verified by comparison with direct pleural pressure measurements over the range of -3 to -34 cm H2O. The pleural pressure changes remained constant for at least 14 weeks following surgery, and there was no evidence of tissue damage or growth around the catheter. This novel method for measuring pleural pressure chronically in conscious rats will facilitate evaluation of the effects of drugs, environmental agents, or disease on respiratory function by allowing repeated and simultaneous measurements of both ventilatory (breathing) patterns and lung function in conscious animals.

Evaluation of an automated pyrogallol red-molybdate method for the measurement of urinary protein in rats.

Methods for quantitating urinary protein differ in their ranges of linearity, technical ease of performance, and applicability to automated analyzers. The Coomassie Brilliant Blue method is widely used but has limited linearity and its tendency to stain glassware has limited its application to automated analyzers. We evaluated a pyrogallol red-molybdate protein dye-binding method (Biotrol USA, Inc.) on a Hitachi 705 analyzer for the quantitation of urinary protein in rats. This method showed a wide range of linearity (up to 2.6 g/l) and good precision. Within-run CVs of 6.6% and 1.3% and between-day CVs of 10.9% and 1.1% were observed at mean protein concentrations of 0.16 g/l and 1.96 g/l, respectively. In addition, rat urine protein results from this method correlated well (r2 = 0.998, n = 40) with a Coomassie Brilliant Blue method (QuanTtest Blue, Quantimetrix Corporation). No significant or unexpected interferences were encountered with this method. We conclude that the automated pyrogallol red-molybdate method is an acceptable and practical alternative to the Coomassie Brilliant Blue method for the quantitation of urine protein in rats.

Phagocytosis, killing, and oxidant production by bovine monocyte-derived macrophages upon exposure to Brucella abortus strain 2308.

Phagocytosis and intracellular survival of Brucella abortus, and oxidant production by monocyte-derived macrophages from ten B. abortus-naive cows were studied. Phagocytosis of bacteria opsonized with naive-autologous sera or reactor serum was significantly less than phagocytosis of bacteria opsonized with fetal bovine serum. After phagocytosis, intracellular survival of bacteria opsonized with naive-autologous or reactor sera was significantly less than survival of bacteria opsonized with fetal bovine serum. Production of oxidant by macrophages stimulated with B. abortus opsonized with naive-autologous, reactor, or fetal bovine sera was not significantly different. Although macrophages from one animal showed significantly less phagocytic activity, intracellular killing and oxidant production by macrophages from the ten individual cows toward B. abortus opsonized with naive-autologous, reactor, and fetal calf sera were homogeneous. The abilities of the macrophages to phagocytize and to kill B. abortus were not associated with each other or with oxidant production. Innate resistance or sensitivity to B. abortus was not identified in the cows based on macrophage function.

Chronic (1-year) safety evaluation of ipazilide fumarate, an antiarrhythmic agent, administered orally to rats.

Ipazilide fumarate (WIN 54177-4) is a chemically novel antiarrhythmic agent that prolongs ventricular refractoriness and possesses antiectopic activity. The compound is being developed as oral and iv therapy for ventricular and supraventricular arrhythmias. Since ipazilide therapy may require long-term use, a 1-year oral gavage study (daily dosages of 20, 80, or 160 mg/kg) was conducted in rats. Controls received the purified water vehicle. Treatment-related clinical signs were limited to post-dosing salivation. Increased relative liver weight (females, at 80 and 160 mg/kg) was correlated with centrilobular hypertrophy, but was not associated with significant increased serum liver enzymes activities. These liver weight changes were interpreted as an adaptive metabolic response and were not considered toxicologically significant. An increased incidence of centrilobular hepatocellular vacuolation representing lipid accumulation over that observed for male controls occurred for males in all ipazilide-treated groups. This observation, however, was not correlated with elevated hepatic enzyme activities. Hepatocellular basophilic foci were observed for females only (80 and 160 mg/kg groups); however, the significance of this lesion is unclear. Transient dosage-related duodenal villous atrophy/sloughing was observed for males from the 80 and 160 mg/kg groups. Mild increases in hemoglobin, hematocrit, urea, and creatinine (160 mg/kg), attributed to treatment, were considered of minor toxicologic importance. Likewise, no clinical or anatomical pathologic observations that may indicate cardiac toxicity were determined. It is concluded that a dosage of 20 mg/kg (two to three times the clinical efficacious dosage) was considered a no-effect dosage level since it did not produce any effects of toxicological significance.

Clinical pathologic alterations associated with subcutaneous administration of recombinant human interleukin-4 to cynomolgus monkeys.

Recombinant human interleukin 4 (rhuIL-4) is a candidate for the treatment of refractory cancer based on its potential to enhance immune function. Recombinant human IL-4 was administered subcutaneously at 0, 1, 5, or 25 micrograms/kg/day for 28 days with a 14-day recovery to male and female cynomolgus monkeys as part of the preclinical safety evaluation. Clinical pathologic changes related to treatment with rhuIL-4 were evidence of consumptive coagulopathy, erythrocyte fragmentation, lymphocytosis, and lymphocyte morphologic changes indicative of marked antigenic or mitogenic stimulation, mild eosinophilia and neutrophilia, hypoalbuminemia, hypocholesterolemia, and hypertriglyceridemia. Based on data obtained after the 14-day recovery period, the clinical pathologic changes associated with rhuIL-4 administration were considered to be reversible.

Preclinical evaluation of recombinant human interleukin-4.

Recombinant human IL-4 (rhuIL-4) is primate-specific and produces multiple biologic effects on lymphoid cells involved in protection against cancer. RhuIL-4 was evaluated in the cynomolgus monkey to support clinical studies for the immunotherapy of cancer. Administration of rhuIL-4 to monkeys by SC injection of 0, 0.5, 2.5 or 12.5 micrograms/kg BID for one-month (with two-week recovery) resulted in alterations in clinical chemistry and hematology (CCH) parameters consistent with a consumptive coagulopathy. Histomorphologic evaluation revealed increased granulopoiesis, testicular atrophy, and proliferative and inflammatory vascular lesions (VL). IVL principally affected the arterial tree with some proliferation of medial smooth muscle. During the latter part of the treatment and recovery period. CCH parameters approached or returned to pretreatment values, the former finding attributed to the production of antibody to rhuIL-4. At final necropsy, bone marrow appeared normal, and IVL decreased in incidence and severity. ELISA studies of serum indicated 50-90% of the monkeys developed antibody titers > 1000 by Day 22 (not observed in man). The frequency and severity of adverse effects due to rhuIL-4 in the clinic appear to be does-related and reversible with few objective responses to therapy observed. Common toxicities included milk to moderated fever and fatigue and an occasional change in hematopoietic, hepatic and renal function. The monkey predicted hematologic findings, but not all target organ effects.

Comparison of oxidant production by bovine neutrophils and monocyte-derived macrophages stimulated with Brucella abortus strain 2308.

Oxidant production by bovine monocyte-derived macrophages and neutrophils was compared after stimulation with phorbol myristate acetate (PMA), opsonized zymosan (OZ), and B. abortus opsonized with naive-autologous, reactor, or fetal bovine sera. Neutrophils responded more rapidly to all stimuli and produced up to 100-fold greater oxidant than did equal numbers of bovine monocyte-derived macrophages. Macrophages and neutrophils stimulated with PMA, OZ, and reactor-opsonized B. abortus had higher mean oxidant production than phagocytes exposed to B. abortus opsonized with autologous sera, fetal bovine serum, or nonopsonized bacteria. Stimulation of macrophages by opsonized zymosan, buffer, and B. abortus opsonized with autologous sera, reactor serum, or fetal bovine serum resulted in low levels of oxidant production that were not significantly different. Only PMA caused a significantly higher level of oxidant production by macrophages.

Arthrotomy versus arthroscopy and partial synovectomy for treatment of experimentally induced infectious arthritis in horses.

To evaluate the clinical, laboratory, and histologic effects of 2 methods of treatment for infectious arthritis in horses, Staphylococcus aureus (3.4 to 3.9 x 10(3) colony-forming units) was inoculated into the tarsocrural joints of 8 horses on day 0. Each horse was treated with phenylbutazone (2 g, PO, q 24 h) and gentamicin sulfate (2.2 mg/kg of body weight, IV, q 8 h) for 14 days. On day 2, general anesthesia was induced, and each horse had 1 tarsocrural joint treated by arthrotomy, with removal of accessible fibrin and lavage with 3 L of sterile balanced electrolyte solution. An indwelling plastic drain was placed in the standing horse to provide a means for lavage with 3 L of balanced electrolyte solution twice daily for 72 hours. The contralateral tarsocrural joint was treated via arthroscopic debridement, synovectomy, and lavage with 3 L of balanced electrolyte solution. Arthrotomy and arthroscopic portals were allowed to heal by second intention. Lameness and thermographic examinations, analysis and bacteriologic culture of synovia, CBC, and WBC differential count were performed prior to inoculation and on days 1, 3, 6, 8, and 13. On day 14, each horse was euthanatized, and the joints were measured, opened, and photographed. Synovium and articular cartilage were obtained for semiquantitative histologic (H&E stain) and histochemical (safranin O fast green stain) evaluation. Lameness and joint circumference were significantly (P less than 0.05) greater in limbs treated by arthroscopy, synovectomy, and lavage. Arthrotomy with lavage eliminated the S aureus infection significantly (P less than 0.05) earlier than arthroscopy, synovectomy, and lavage, however, both treatments eliminated the infection in all but a single joint.(ABSTRACT TRUNCATED AT 250 WORDS)

Pre-clinical toxicity of IL-4: a model for studying protein therapeutics.

The purpose of this presentation was to review issues and findings in the pre-clinical development and evaluation of recombinant human protein therapeutics. Since human cytokines and lymphokines are endogenous proteins, their pre-clinical development and evaluation would seem straightforward and their toxicities minimal. Unfortunately, the pre-clinical development of this class of agents has been problematic and confounding. Some of the clinical toxicities and pharmacodynamics have been predicted by the pre-clinical evaluation and others have not. Some molecules are species specific which limits species selection for pre-clinical evaluation. Other confounding issues include: route of exposure, synergy of toxicity with other lymphokines, length of study design, immunogenicity, predictiveness of pre-clinical evaluation and iatrogenic toxicities. An approach used by SWPRD in the evaluation of this class of molecules was discussed. Insight gained during the pre-clinical and clinical development of these molecules should simplify the further development of protein therapeutics that follow. Specific studies with recombinant human interleukin-4 (rhuIL-4) were reviewed in detail as part of a pre-clinical safety evaluation. Native IL-4 has properties that exemplify many of the immune recognition-induced lymphokines and is produced principally by activated T-lymphocytes CD4+. It is a co-factor in B-cell proliferation and enhances ex vivo B-cell expansion and is believed to be a candidate for the treatment of refractory cancer based on this immune enhancement ability. rhuIL-4 is a 15,400 molecular weight cytokine produced in a yeast expression system.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of ketamine hydrochloride on serum biochemical and hematologic variables in rhesus monkeys (Macaca mulatta).

Serum biochemical and hematologic values were obtained from Rhesus monkeys (Macaca mulatta) before and 15 minutes after intramuscular injection with ketamine hydrochloride (5-10 mg/kg). A 345% increase in serum creatine kinase activity 15 minutes after ketamine administration was attributed to muscle damage caused by the injection. Decreases in erythrocyte count, hemoglobin, hematocrit, total leukocyte count, lymphocyte count, and the serum concentrations of glucose, total protein, albumin, and other serum analytes were all attributed to the reversal (by ketamine) of the excitement or "alarm reaction" associated with physical restraint. The decrease in circulating erythrocytes and lymphocytes indicated a redistribution of these cells from the circulating blood to the spleen and extravascular sites, respectively. Decreases in concentrations of total protein, albumin, and several other serum analytes suggested an influx of fluid into the vascular space. The decrease in glucose may also reflect the reversal of an epinephrine-induced hyperglycemia in the excited awake monkey. These alterations should be considered when designing studies and interpreting data for Rhesus monkeys.

Quantitative urinalysis in kittens from four to thirty weeks after birth.

To evaluate renal function and obtain reference values for measurements of urinary excretion of various substances, quantitative urinalysis was performed in healthy, growing kittens from 4 to 30 weeks after birth. Endogenous creatinine clearance, 24-hour urine protein excretion, and urine protein-to-creatinine ratio were determined. Additionally, fractional excretion to creatinine clearance was calculated for calcium, inorganic phosphorus, sodium, potassium, and chloride. Mean +/- SD endogenous creatinine clearance values (range, 3.80 +/- 0.48 to 4.74 +/- 0.61 ml/min/kg) were significantly (P less than 0.0001) higher in kittens 9 to 19 weeks old, compared with younger (range, 1.39 +/- 0.85 to 3.59 +/- 0.86 ml/min/kg) and older kittens (range, 2.69 +/- 0.40 to 3.46 +/- 0.37 ml/min/kg). Mean values for all kittens for 24-hour urine protein excretion (range, 2.54 +/- 1.81 mg/kg at 4 weeks to 11.39 +/- 7.61 mg/kg at 14 weeks) and for urine protein-to-creatinine ratio (range, 0.14 +/- 0.03 to 0.34 +/- 0.18) varied from week to week of age. The urine protein-to-creatinine ratio in kittens greater than or equal to 9 weeks old correlated well (R2 = 0.861) with 24-hour urine protein excretion. Urinary fractional excretion of calcium, inorganic phosphorus, sodium, potassium, and chloride in kittens varied among age groups, being significantly (P less than 0.01) different for potassium and calcium in young kittens (4 to 6 weeks) and older kittens (greater than or equal to 7 weeks).

Clinical, clinicopathologic, and parasitologic observations of trypanosomiasis in dogs infected with North American Trypanosoma cruzi isolates.

Nineteen purebred Beagles of various ages (4, 5, 13, and 47 weeks) were inoculated with North American Trypanosoma cruzi isolates obtained from an opossum (Tc-O), an armadillo (Tc-A), or a dog (Tc-D). Dogs were grouped on the basis of clinical outcome of infection. During the acute stage of disease, dogs of group 1 (n = 7 inoculated with Tc-O or Tc-A) died or were euthanatized because of the severity of disease. Dogs of group 2 (n = 5 inoculated with Tc-O or Tc-A) developed acute disease, but survived to develop chronic disease. Dogs of group 3 (n = 7 Tc-D-inoculated dogs) developed neither acute nor chronic disease. Dogs of group 4 (n = 4--2 dogs 13 weeks old and 2 dogs 47 weeks old) served as noninoculated controls. Clinical signs associated with severe acute myocarditis developed in dogs of groups 1 and 2 between postinoculation day (PID) 15 and 28. Generalized lymphadenopathy and lymphocytosis were observed in all dogs of groups 1, 2, and 3 between PID 14 and 17. Serum alanine transaminase and aspartate transaminase activities and urea nitrogen concentration were high, and glucose concentration was low prior to death of dogs in group 1. Serum activities of isoenzymes of creatine kinase were significantly (P less than 0.05) high in only 1 dog (group 1), whereas serum lactate dehydrogenase isoenzyme activities were not significantly high in any dog.(ABSTRACT TRUNCATED AT 250 WORDS)

Histomorphologic observations for cynomolgus monkeys after subchronic subcutaneous injection of recombinant human interleukin-4.

Recombinant human interleukin-4 (rhuIL-4) is a candidate for the treatment of refractory cancer based on its potential to enhance the function of the immune system. Total daily dosages of 0 (placebo control), 1, 5, or 25 micrograms/kg of rhuIL-4 were given as divided (b.i.d.) subcutaneous dosages to male and female cynomolgus monkeys (5/sex/group) for 1 month followed by a 2-week recovery. Histomorphologic evaluation of 3/sex/group at 1 month revealed vascular lesions, granulocytic hyperplasia, and seminiferous tubular atrophy attributed to treatment with rhuIL-4. Dosage-dependent proliferative and inflammatory vascular lesions with eosinophil infiltration affected principally the arterial tree. After 2 weeks of recovery, these lesions, including chronic endarteritis and chronic and/or obliterative arteritis, occurred with an overall lower incidence, and were not observed for monkeys from the 1.0 micrograms/kg/day group. Granulocytic hyperplasia in bone marrow observed for monkeys from all groups given rhuIL-4 at 1 month was not present after 2 weeks of recovery. Seminiferous tubular atrophy was observed for monkeys from the 5 and 25 micrograms/kg/day groups at 1 month and after 2 weeks of recovery.

Effect of acute acidemia on blood biochemical variables in healthy ponies.

L-Lactic acid and D,L-lactic acid infusion in ponies resulted in metabolic acidosis with high anion gap (AG). Increased AG was explained entirely by increased blood L- and D-lactate concentrations. Hydrochloric acid infusion caused metabolic acidosis with decreased AG. Saline (NaCl) infusion caused mild metabolic acidosis, with no significant change in AG. Plasma K+ concentration was decreased by all types of infusions, with a maximum of 0.50, 0.25, 0.40, 0.50 mmol/L below baseline at the end of infusion in the L-lactic acid-, D,L-lactic acid-, HCl-, and NaCl-infused ponies, respectively. Only hydrochloric acid had a tendency to increase plasma K+ concentration. Hypophosphatemia developed in NaCl- and HCl-infused ponies, but not in the D,L-lactic acid-infused ponies. Serum inorganic phosphate concentration in L-lactic acid-infused ponies increased initially, but was significantly (P less than 0.05) lower than values in the other ponies at 4 hours after onset of infusion. In ponies, the effect of acidemia on plasma K+ and serum inorganic phosphate concentrations was similar to that reported for other species. Changes were small in magnitude and depended on the nature of the acid anion. Results indicate that large changes in plasma K+ and serum inorganic phosphate concentrations during acidosis are probably not a direct result of acidemia.

Blood biochemical response to sodium bicarbonate infusion during sublethal endotoxemia in ponies.

Hypertonic NaHCO3 infusion caused blood volume expansion, increased blood bicarbonate concentration, and delayed the onset of hypophosphatemia in ponies with endotoxemia. However, NaHCO3 infusion did not normalize blood pH, and it increased blood L-lactate concentration, and caused hypokalemia, hypernatremia, and hyperosmolality. The deleterious effects of NaHCO3 infusion in endotoxemia ponies outweighed the beneficial effects. The role of hypertonic NaHCO3 given IV for treatment of endotoxemia in equids must be reevaluated.

Effect of hypertonic vs isotonic saline solution on responses to sublethal Escherichia coli endotoxemia in horses.

Cardiovascular responses to sublethal endotoxin infusion (Escherichia coli, 50 micrograms/ml in lactated Ringer solution at 100 ml/h until pulmonary arterial pressure increased by 10 mm of Hg) were measured 2 times in 5 standing horses. In a 2-period crossover experimental design, horses were either administered hypertonic (2,400 mosm/kg of body weight, IV) or isotonic (300 mosm/kg, IV) NaCl solution after endotoxin challenges. Each solution was administered at a dose of 5 ml/kg (infusion rate, 80 ml/min). Complete data sets (mean arterial, central venous, and pulmonary arterial pressures, pulmonary arterial blood temperature, cardiac output, total peripheral vascular resistance, heart rate, plasma osmolality, plasma concentration of Na, K, Cl, and total protein, blood lactate concentration, and PCV) were collected at 0 (baseline, before endotoxin infusion), 0.25, 1, 1.5, 2, 2.5, 3, 3.5, 4, and 4.5 hours after initiation of the endotoxin infusion. Blood constituents alone were measured at 0.5 hour and cardiovascular variables alone were evaluated at 0.75 hour. By 0.25 hour, endotoxin infusion was completed, a data set was collected, and saline infusion was initiated. By 0.75 hour, saline solutions had been completely administered. Mean (+/- SEM) cardiac output decreased (99.76 +/- 3.66 to 72.7 +/- 2.35 ml/min/kg) and total peripheral resistance (1.0 +/- 0.047 to 1.37 +/- 0.049 mm of Hg/ml/min/kg) and pulmonary arterial pressure (33.4 +/- 0.86 to 58.3 +/- 1.18 mm of Hg) increased for both trials by 0.25 hour after initiation of the endotoxin infusion and prior to fluid administration. For the remainder of the protocol, cardiac output was increased and total peripheral resistance was decreased during the hypertonic, compared with the isotonic, saline trial.(ABSTRACT TRUNCATED AT 250 WORDS)