Preclinical trial of doxorubicin entrapped in sterically stabilized liposomes in dogs with spontaneously arising malignant tumors

PURPOSE

To prospectively evaluate the short-term toxicoses associated with pegylated-liposomal doxorubicin (Doxil) administered to dogs with measurable tumors of various histologic types and sites. Preliminary information regarding efficacy was also generated.

METHODS

A group of 51 dogs with histologically confirmed malignancies received a total of 103 Doxil treatments given i.v. every 3 weeks at dosages ranging from 0.75 to 1.1 mg/kg in the context of a phase I dose-escalation trial. Acute and short-term toxicities as well as tumor response and duration of response were characterized.

RESULTS

The maximally tolerated dose in tumor-bearing dogs was established as 1.0 mg/kg i.v. every 3 weeks. The dose-limiting toxicity was a cutaneous toxicity clinically resembling palmar-plantar erythrodysesthesia (PPES). An overall response rate of 25.5% was observed with five complete responders and eight partial responders.

CONCLUSIONS

Doxil appeared to be well tolerated at dosages similar to those tolerated for free doxorubicin in tumor-bearing dogs. PPES was the dose-limiting toxicity encountered, rather than myelosuppresion as is the case with free doxorubicin in dogs. Doxil as a single agent may have a broad spectrum of activity and deserves further evaluation.

SK&F 86002, a dual cytokine and eicosanoid inhibitor, attenuates endotoxin-induced cardiopulmonary dysfunction in the pig

Cytokines and eicosanoids are well documented important mediators of endotoxemia. Bicyclic imidazoles are a novel class of nonsteroidal anti-inflammatory compounds that display unique pharmacological profiles by reducing cytokine production and arachidonic acid metabolism. In this study, we evaluated the ability of the bicyclic imidazole, SK&F 86002, to attenuate endotoxin-induced cardiopulmonary dysfunction. Pigs were randomly assigned to one of four groups: LPS (n = 5), given .5 microgram/kg/h 055:B5 Escherichia coli lipopolysaccharide (LPS) intravenously (i.v.) for 6 h; saline (n = 5); SK&F 86002 (n = 3), given 50 mg/kg SK&F 86002 orally 30 min prior to anesthesia; and SK&F 86002 + LPS (n = 5). Administration of LPS resulted in cardiopulmonary dysfunction characterized by decreased stroke volume and arterial oxygen tension, and increased room air alveolar-arterial oxygen gradient, pulmonary arterial pressure, pulmonary vascular resistance, and peak intratracheal pressure. Additionally, LPS administration was associated with leukopenia and increased pulmonary myeloperoxidase activity. Pretreatment with SK&F 86002 attenuated LPS induced hypotension, hypoxemia and bronchoconstriction and blocked the pulmonary hypertension. SK&F 86002 blocked the LPS-induced increase in myeloperoxidase activity, indicating a reduction in pulmonary neutrophil infiltration, but had no effect on systemic leukopenia. Pretreatment with SK&F 86002 significantly attenuated LPS-induced increases in plasma thromboxane B2 and tumor necrosis factor-alpha. We hypothesize that ameliorating effects of SK&F 86002 in this endotoxin model of cardiopulmonary dysfunction are related to inhibition of cytokine and eicosanoid biosynthesis.

The effect of nonablative laser energy on joint capsular properties. An in vitro histologic and biochemical study using a rabbit model

The purpose of this study was to evaluate the effect of laser energy at nonablative levels on joint capsular histologic and biochemical properties in an in vitro rabbit model. The medial and lateral portions of the femoropatellar joint capsule from both stifles of 12 mature New Zealand White rabbits were used. Specimens were divided into three treatment groups (5 watts, 10 watts, and 15 watt) and one control group using a randomized block design. Specimens were placed in a 37 degrees bath of lactated Ringer's solution and laser energy was applied using a holmium:yttrium-aluminum-garnet laser in four transverse passes across the tissue at a velocity of 2 mm/sec with the handpiece set 1.5 mm from the synovial surface. Histologic analysis revealed thermal alteration of collagen (fusion) and fibroblasts (pyknosis) at all energy densities, with higher laser energy causing significantly greater morphologic changes over a larger area (P < 0.05). Application of laser energy did not significantly alter the biochemical parameters evaluated, including type I collagen content and nonreducible crosslinks (P > 0.05). This study demonstrated that nonablative laser energy caused significant thermal damage to the joint capsular tissue in an energy-dependent fashion, but type I collagen content and nonreducible crosslinks (P > 0.05). This study demonstrated that nonablative laser energy caused significant thermal damage to the joint capsular tissue in an energy-dependent fashion, but type I Collagen content and nonreducible corsslinks were not significantly altered.

Participation of lymphocyte subpopulations in the pathogenesis of experimental murine cerebral malaria

We determined the requirement for selected lymphocyte subsets and cytokines in the pathogenesis of experimental murine cerebral malaria (CM) by using gene-targeted knockout and mAb-suppressed mice. Plasmodium berghei ANKA infection induced CM in A 0/0 mice, which lack expression of surface MHC class II glycoproteins and consequently express a severe and chronic reduction in numbers of CD4+ T cells. However, when A 0/0 mice, which are on a C57BL/6 x 129 genetic background, or immune-intact C57BL/6 controls treated with anti-CD4 mAb were infected, none developed CM. The latter finding confirms an earlier report that CD4+ T cells are required for CM to occur and additionally indicates that the reduced numbers of CD4+ T cells present in A 0/0 mice are sufficient for CM development. Neither the recently described CD4+, NK1.1+ T cell subset shown to be present in A 0/0 mice nor traditional NK cells seem to be required for the induction of CM because A 0/0 and C57BL/6 mice severely depleted of both NK1.1+ populations with mAb developed CM as readily as did normal Ig-treated controls. Deficiency of Th1-associated cytokines (IFN-gamma or IL-2) in mice by gene-targeted disruptions completely inhibited CM development, whereas the lack of Th2-associated cytokines (IL-4 or IL-10) did not prevent this disease. Our observation that B cell-deficient JHD and microMT mice developed CM provides evidence that neither B cells, their products, nor B cell Ag presentation are a requisite for CM pathology. We further observed that neither beta 2m 0/0 knockout mice, which lack CD8+ alpha beta T cells, nor C57BL/6 mice depleted of CD8+ T cells with anti-CD8 mAb treatment developed CM, leading us to conclude that CD8+ T cells are also crucial for the development of CM.

Participation of lymphocyte subpopulations in the pathogenesis of experimental murine cerebral malaria

We determined the requirement for selected lymphocyte subsets and cytokines in the pathogenesis of experimental murine cerebral malaria (CM) by using gene-targeted knockout and mAb-suppressed mice. Plasmodium berghei ANKA infection induced CM in A 0/0 mice, which lack expression of surface MHC class II glycoproteins and consequently express a severe and chronic reduction in numbers of CD4+ T cells. However, when A 0/0 mice, which are on a C57BL/6 x 129 genetic background, or immune-intact C57BL/6 controls treated with anti-CD4 mAb were infected, none developed CM. The latter finding confirms an earlier report that CD4+ T cells are required for CM to occur and additionally indicates that the reduced numbers of CD4+ T cells present in A 0/0 mice are sufficient for CM development. Neither the recently described CD4+, NK1.1+ T cell subset shown to be present in A 0/0 mice nor traditional NK cells seem to be required for the induction of CM because A 0/0 and C57BL/6 mice severely depleted of both NK1.1+ populations with mAb developed CM as readily as did normal Ig-treated controls. Deficiency of Th1-associated cytokines (IFN-gamma or IL-2) in mice by gene-targeted disruptions completely inhibited CM development, whereas the lack of Th2-associated cytokines (IL-4 or IL-10) did not prevent this disease. Our observation that B cell-deficient JHD and microMT mice developed CM provides evidence that neither B cells, their products, nor B cell Ag presentation are a requisite for CM pathology. We further observed that neither beta 2m 0/0 knockout mice, which lack CD8+ alpha beta T cells, nor C57BL/6 mice depleted of CD8+ T cells with anti-CD8 mAb treatment developed CM, leading us to conclude that CD8+ T cells are also crucial for the development of CM.

Force-plate analysis of gait before and after surgical excision of calcified lesions of the supraspinatus tendon in two dogs

Two dogs with supraspinatus calcifying tendinopathy were lame in their forelimbs and were treated by the surgical excision of the calcified lesion. The lameness in both dogs improved after surgery without additional medical treatment, as evidenced by force-plate analysis of their gait.

Laparoscopic methods for castration of equids

OBJECTIVE

To evaluate 2 laparoscopic techniques for castration of horses.

DESIGN

Prospective, randomized trial.

ANIMALS

6 sexually intact male ponies.

PROCEDURE

Ponies were anesthetized and placed in dorsal recumbency. By means of restricted randomization, 1 testis in each pony was selected to undergo in situ destruction (i.e., vascular cauterization and ligation with the testis left in situ); the other testis was pulled back into the abdomen and removed. Baseline and stimulated testosterone concentrations were determined preoperatively and postoperatively. After euthanasia, the in situ testes were examined histologically.

RESULTS

There were no surgical complications. In all ponies, postoperative baseline and stimulated testosterone concentrations were consistent with castration. The testicular parenchyma of the testes that had been left in situ underwent coagulative necrosis.

CLINICAL IMPLICATIONS

In ponies and juvenile stallions, normally descended testes can be removed laparoscopically. Nonpalpable inguinal testes can be left in situ after laparoscopically ligating and transecting the testicular artery and vein. Additional experience with these approaches is necessary before their use can be recommended in mature stallions.

Effects of potentiated chlorhexidine on bacteria and tarsocrural joints in ponies

OBJECTIVES

To evaluate the bactericidal properties of chlorhexidine diacetate (CHD) after potentiation with EDTA and Tris buffer (EDTA-Tris), and to find a potentiated CHD concentration that would achieve 90 to 100% killing for all bacteria tested.

ANIMALS

6 adult ponies.

PROCEDURES

Serial dilutions of CHD, CHD in EDTA-Tris and EDTA-Tris alone were evaluated for bactericidal activity against Staphylococcus aureus, Escherichia coli, and Streptococcus zooepidemicus. The tarsocrural joints of 6 ponies were lavaged with either 1 L phosphate-buffered saline solution (control) or 1 L of 0.0005% CHD in EDTA-Tris. Synovial fluid was collected before lavage and on days 1,4, and 8. Synovia, cartilage, and bone with cartilage were collected on day 8 when the ponies were euthanatized.

RESULTS

In vitro results indicated that 0.0005% CHD in EDTA-Tris was 90% lethal to all bacteria tested. Results of synovial fluid analysis, glycosaminoglycan analysis, and histologic examination of the synovial membrane and articular cartilage indicated that joint lavage with 0.0005% CHD in EDTA-Tris was not detrimental to the synovium or the articular cartilage of pony tarsocrural joints. Changes observed were a result of the actual lavage process, the phosphate-buffered saline solution, and hemarthrosis.

CONCLUSIONS

A concentration of 0.0005% CHD in EDTA-Tris was 90% lethal to all bacteria tested. Pony tarsocrural joint lavage with 0.0005% CHD in EDTA-Tris was not detrimental to the synovium or the articular cartilage. The efficacy of 0.0005% CHD potentiated with EDTA-Tris as a potential joint lavage fluid for treatment of infectious arthritis needs to be evaluated in clinical patients.

Zygomatic osteoma with atypical heterogeneity in a dog

An osteoma of the zygomatic bone in a young dog is described. It had large, centralized radiolucent regions consisting of fatty bone marrow and sparse trabeculae. A discrete, proliferative nodule within the osteoma consisted of closely-packed woven bone trabeculae and pleomorphic osteoblasts associated with haphazard osteoid deposits, resembling osteosarcoma-like change. These heterogeneous structural features were at variance with more classic reports of osteoma, which usually describe a uniform cancellous or cortical bone architecture.

Mycobacterial keratitis in a parrot

Histologic examination revealed acid-fast organisms in a granulomatous lesion involving the cornea of an eye of a Maximilian's Parrot. Disseminated mycobacteriosis was also diagnosed. Antemortem attempts at determining the cause of the corneal lesion had been unsuccessful. Ocular involvement in birds with avian tuberculosis is uncommon. The corneal lesion in the parrot was likely initiated by a dysfunctional third eyelid.

Effects of 0.05% chlorhexidine lavage on the tarsocrural joints of horses

In six horses, a 0.05% solution of chlorhexidine diacetate was used to lavage one tarsocrural joint; the contralateral control joint was lavaged with lactated Ringer's solution. Horses were evaluated daily for lameness. Synovial fluid samples were collected on days 1, 4, and 8 for determination of protein concentration, total and differential leukocyte counts, and mucin clot formation. After death on day 8, synovium and osteochondral samples were collected from the tarsocrural joints for examination of morphology and proteoglycan staining. Lavage with chlorhexidine solution caused lameness that was reduced but still evident at day 8. Synovial protein concentration was significantly increased by chlorhexidine lavage; the greatest increase occurred on day 1. Joint lavage increased synovial leukocyte counts on day 1, primarily by increasing polymorphonuclear (PMN) cell counts. Although total synovial leukocyte counts returned to normal by day 4, PMN cell counts remained elevated through day 8; PMN cell counts for chlorhexidine-lavaged joints were typically twice that of control joints. Chlorhexidine lavage caused synovial ulceration, inflammation, and abundant fibrin accumulation. Consistent differences in proteoglycan staining were not detected between control and chlorhexidine-lavaged joints. Joint lavage with 0.05% chlorhexidine diacetate, the lowest known bactericidal concentration, is not recommended for equine joints.

Methimazole protection of rats against gentamicin-induced nephrotoxicity

Methimazole was previously shown to protect rats, mice, and (or) dogs against cisplatin-, cephaloridine-, 2-bromohydro-quinone-, and S-(1,2-dichlorovinyl)-L-cysteine-induced nephrotoxicity. In this study, methimazole effects on gentamicin (GM) induced nephrotoxicity were examined. Rats given GM (40 mg/kg) twice daily for 10 days exhibited higher blood urea nitrogen (BUN) concentrations and severe necrosis of virtually all proximal tubules compared with saline-treated controls. Rats cotreated with methimazole (20 mg/kg) exhibited minimal proximal tubular necrosis and were protected against GM-induced increase in BUN concentrations, despite having higher kidney GM concentrations. Rats given GM alone for 3 days exhibited no proximal tubular necrosis and no elevation of BUN values. However, these rats exhibited an increase in nonprotein disulfide concentrations and a decrease in renal protein thiol and protein disulfide concentrations, as opposed to rats given GM and methimazole. Together the results show that methimazole was an effective antagonist of GM-induced nephrotoxicity. Methimazole did not inhibit GM renal uptake but may protect against GM-induced nephrotoxicity by acting as an antioxidant within the kidneys.

Roles of cysteine conjugate beta-lyase and S-oxidase in nephrotoxicity: studies with S-(1,2-dichlorovinyl)-L-cysteine and S-(1,2-dichlorovinyl)-L-cysteine sulfoxide

Effects of S-(1,2-dichlorovinyl)-L-cysteine (DCVC) and its putative metabolite DCVC sulfoxide (DCVCO) on renal function in vivo and in vitro were investigated to assess the role of sulfoxidation in the mechanism of toxicity of cysteine S-conjugates. Both conjugates were potent nephrotoxicants in rats in vivo, but at equimolar doses, DCVCO produced greater renal injury (i.e., increases in blood urea nitrogen levels and anuria and more severe and widespread proximal tubular necrosis) than DCVC. Pretreatment of rats with aminooxyacetic acid (AOAA), a selective cysteine conjugate beta-lyase (beta-lyase) inhibitor, did not protect against DCVCO nephrotoxicity, whereas rats given DCVC and AOAA exhibited partial protection. These results suggest that in addition to cleavage by the beta-lyase, sulfoxidation by the cysteine conjugate S-oxidase (S-oxidase) may play a role in DCVC nephrotoxicity. In isolated rat kidney proximal tubular (PT) and distal tubular (DT) cells, both DCVC and DCVCO produced time- and concentration-dependent increases in the release of lactate dehydrogenase. Because DCVC was generally more toxic in PT cells and DCVCO was more toxic in DT cells, an attempt was made to correlate in vitro cytotoxicity with the cellular distribution of the beta-lyase and S-oxidase. The finding that beta-lyase activity exhibited a 2-fold higher Vmax/Km ratio in PT cells than in DT cells, the greater inhibition of both beta-lyase activity and DCVC toxicity by AOAA in PT cells than in DT cells and the lower (40%) S-oxidase activity in PT cells than in DT cells provide evidence for the importance of the beta-lyase in DCVC toxicity in PT cells. The finding that DCVCO was more toxic in DT cells than in PT cells and the inability of AOAA to protect DT cells from DCVC-induced cytotoxicity, however, provide further evidence for DCVC bioactivation by S-oxidase.(ABSTRACT TRUNCATED AT 250 WORDS)

An influenza A (H1N1) virus, closely related to swine influenza virus, responsible for a fatal case of human influenza

In July 1991, an influenza A virus, designated A/Maryland/12/91 (A/MD), was isolated from the bronchial secretions of a 27-year-old animal caretaker. He had been admitted to the hospital with bilateral pneumonia and died of acute respiratory distress syndrome 13 days later. Antigenic analyses with postinfection ferret antisera and monoclonal antibodies to recent H1 swine hemagglutinins indicated that the hemagglutinin of this virus was antigenically related to, but distinguishable from, those of other influenza A (H1N1) viruses currently circulating in swine. Oligonucleotide mapping of total viral RNAs revealed differences between A/MD and other contemporary swine viruses. However, partial sequencing of each RNA segment of A/MD demonstrated that all segments were related to those of currently circulating swine viruses. Sequence analysis of the entire hemagglutinin, nucleoprotein, and matrix genes of A/MD revealed a high level of identity with other contemporary swine viruses. Our studies on A/MD emphasize that H1N1 viruses in pigs obviously continue to cross species barriers and infect humans.

Antigenic and genetic analysis of a recently isolated H1N1 swine influenza virus

Hemagglutinins (HA) of H1N1 swine influenza viruses isolated in the United States have remained antigenically and genetically conserved for many years. In contrast to such conservation, the HA of A/Swine/Nebraska/1/92 (Sw/Neb) could readily be distinguished from those of contemporary porcine viruses. Twenty-eight amino acid mutations differentiated the HA of Sw/Neb and A/Swine/Indiana/1726/88, the most recent H1N1 swine influenza virus for which HA sequence data were available. Among these differences were mutations at potential asparagine-linked glycosylation sites and charge changes at many residues. The Sw/Neb virus also could be differentiated from other swine influenza viruses in hemagglutination-inhibition assays with monoclonal antibodies to recent H1 swine HA. Nonetheless, overall sequence analysis of the HA and the nucleoprotein genes of Sw/Neb indicated that this virus was more closely related genetically to classic H1N1 swine influenza viruses than to H1N1 avian or human viruses. Infection of swine with Sw/Neb under experimental conditions induced clinical signs and lesions typical of swine influenza. However, affected swine in the field had high, persistent fevers, but relatively mild signs of respiratory tract disease. This study indicated that an antigenically and genetically novel variant of swine influenza virus was detected in the United States.

Fumonisin toxicosis in swine: clinical and pathologic findings

From a series of experimental studies with pigs (12-16 kg), either pulmonary edema or liver failure emerged as a distinct pathogenetic expression of fumonisin B1 (FB1) toxicosis. The primary determinant as to which pathogenetic consequence developed was the quantity (dose) of the mycotoxin fed or intubated per kilogram of body weight per day. Pigs intubated with a minimum of 16 mg FB1/kg/day developed severe interlobular edema with or without hydrothorax and variably severe pulmonary edema. Pigs intubated with < 16 mg FB1/kg/day or pigs fed diets containing 200 mg FB1/kg of feed developed marked icterus and hepatocellular necrosis. The spectrum of degrees of severity of pulmonary edema observed in the experimental pigs allowed rational speculation regarding evolution of the pathologic changes.

Isolation of feline eosinophils via peritoneal lavage

Fourteen cats were inoculated orally with 1 of 2 infective doses of Toxocara canis to induce eosinophilia. Cats were subsequently challenge exposed twice via intraperitoneal injection with 1 of 2 T canis antigen preparations. Peritoneal lavage was performed 2 days after antigenic challenge exposure, and eosinophils in the peritoneal lavage fluid were quantified. None of the cats developed clinical signs of disease after infection. All cats developed peripheral eosinophilia after infection. Significant (P < 0.05) difference in mean eosinophil count from the lavage fluid was observed between lavage 1 (prechallenge exposure) and lavages 2 and 3 (postchallenge exposure) in both groups of cats. Significant difference in eosinophil count was not found between cats given different doses of eggs. After initial challenge exposure, significantly (P < 0.05) more eosinophils were obtained from cats given antigen preparation 2 (prep-2) than from those given antigen prep-1. This difference was no longer observed after the second challenge exposure with higher doses of either antigen prep-1 or prep-2. In cats given antigen prep-2, significant difference was not found between lavages 2 and 3. However, in cats given antigen prep-1, eosinophil count was significantly (P = 0.005) greater in fluid obtained from lavage 3, compared with eosinophil count from lavage 2. Mean +/- SEM percentage of eosinophils in the fluid from lavage 3 in all cats was 70.8 +/- 2.2%. Other cell types included macrophages, neutrophils, lymphocytes, and mast cells. Gross postmortem findings were mild. One- to 3-mm nodular white foci of inflammation were observed on the serosal surfaces of the liver, spleen, kidneys, and omentum.(ABSTRACT TRUNCATED AT 250 WORDS)

Methimazole as a protectant against cisplatin-induced nephrotoxicity using the dog as a model

The protective effect of methimazole, a commonly used antithyroid drug, on cisplatin-induced nephrotoxicity was studied. Eight dogs received 80 mg/m2 cisplatin i.v. without saline prehydration. Dogs were randomized into two groups of four dogs each: one group received 40 mg/kg methimazole i.p. at 30 min prior to and 4 h after cisplatin delivery, and the other group received saline placebo i.p. Methimazole protected dogs against the in vivo nephrotoxicity elicited by cisplatin as evidenced by clinicopathologic and histopathologic indices. Protection was not complete, as methimazole-treated animals developed mild histopathologic renal changes. Measures of renal oxidative stress did not differ between the two groups at day 5 following cisplatin treatment. No difference was noted for serum thyroxine concentrations before or after therapy in either group; however, serum levels of 3,5,3'-triiodothyronine were significantly higher on day 5 in both groups of dogs receiving cisplatin, regardless of whether they received methimazole or not. Methimazole as used in this study was found to be well tolerated in dogs over the short term, with no significant clinical or clinicopathologic toxicity being observed. The results of this study support the additional evaluation of methimazole as a protectant against cisplatin-induced nephrotoxicity using the dog as a model.

Effects of a thromboxane synthetase inhibitor on established immune complex glomerulonephritis in dogs

Twelve Beagles were inoculated with concanavalin A, and after a mean ninefold increase in antibody titer, 1 mg of concanavalin A was infused into each renal artery of each dog to induce in situ immune complex glomerulonephritis. Starting 4 weeks after renal arterial infusion, 6 dogs were treated orally 3 times daily with 30 mg of 3-methyl-2 (3 pyridyl)-1-indolectanoic acid (CGS 12970)/kg of body weight, a thromboxane synthetase inhibitor, and 6 dogs (control group) received a gelatin capsule 3 times daily. Endogenous creatinine clearance and 24-hour urinary excretion of protein and thromboxane B2 were determined for each dog prior to renal arterial infusion, at the initiation of treatment and at 2, 4, 6, and 8 weeks after initiation of treatment. In addition, methyoxy-3H inulin clearance was determined at initiation of treatment and 4 and 8 weeks later. Renal specimens were examined histologically at the initiation of treatment and 4 and 8 weeks later. Glomerular mononuclear profiles/microns 3 were determined from at least 10 equatorially sectioned glomeruli from each dog. Paired t tests were used to compare mean values at the various time points to the respective mean baseline value and 2-sample t tests were used to evaluate differences between treatment groups. At the start of treatment (4 weeks after renal arterial infusion of concanavalin A), histologic evaluation of renal specimens revealed glomerular epithelial crescent formation, mononuclear cell proliferation, and infiltration of neutrophils. Mononuclear cell profiles and urinary excretion of protein and thromboxane B2 were significantly increased, but endogenous creatinine clearance values were unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Methimazole protection of rats against chemically induced kidney damage in vivo

Because methimazole has antioxidant properties, the effects of methimazole treatment on cephaloridine, S-(1,2-dichlorovinyl)-L-cysteine (DCVC), 2-bromohydroquinone (2-BHQ) and cis-diaminedichloroplatinum (II) (cisplatin)-induced nephrotoxicity were investigated. Rats given cephaloridine (1 g/kg), cisplatin (5 mg/kg), DCVC (100 mg/kg) or 2-BHQ (157 mg/kg) i.p. exhibited significant elevations in blood urea nitrogen concentrations, which correlated with appearance of distinct renal histopathological changes. Cephaloridine, DCVC or 2-BHQ-induced nephrotoxicity was reduced only when methimazole (20-40 mg/kg) was given 30 min before the nephrotoxicant, whereas cisplatin-induced nephrotoxicity was reduced when methimazole was given 30 min before and up to 4 hr after cisplatin. Because the renal organic acid transport system plays an important role in the nephrotoxicity of cephaloridine, cisplatin and DCVC, the role of the organic acid transport system in the renal uptake of methimazole was investigated. With rat kidney cortical slices, methimazole uptake was time- and concentration-dependent; however, the organic acid transport substrates, probenecid (1 mM) and p-aminohippuric acid (7.5 mM), were ineffective in blocking methimazole uptake. Furthermore, cephaloridine (1 mM) uptake by kidney cortical slices was not affected by methimazole (5 mM). Rats given methimazole (40 mg/kg) 30 min before cephaloridine (2 g/kg) had serum and kidney cephaloridine concentrations similar to rats given cephaloridine only, but the methimazole-pretreated rats were significantly protected against cephaloridine-induced oxidation of renal nonprotein thiols. These results show that methimazole does not inhibit the transport of cephaloridine into the kidneys, but may protect against cephaloridine-induced renal damage by acting as an antioxidant within the kidneys.

Effects of thromboxane synthetase inhibition on immune complex glomerulonephritis

To determine the role of thromboxane A2 in the pathogenesis of experimentally induced immune complex glomerulonephritis, 12 concanavalin A-immunized Beagles were infused with 1 mg of concanavalin A via each renal artery and treated twice daily for 8 days with either 30 mg of CGS 12970/kg, PO, a specific thromboxane synthetase inhibitor, or placebo. The effect of treatment was assessed by measuring endogenous creatinine clearance and urine protein and eicosanoid excretion, and by evaluating changes in glomerular morphometric characteristics. On postinfusion day 8, urine protein, thromboxane B2, and 11-dehydro-thromboxane B2 excretion, glomerular epithelial crescent formation, and glomerular cell proliferation in the CGS 12970-treated dogs were significantly decreased when compared with values in the placebo-treated group. Differences were not observed in endogenous creatinine clearance, urine prostaglandin E2 and 6-keto-prostaglandin F1 alpha excretion, or glomerular polymorphonuclear leukocyte infiltration between groups in this study. These findings suggest thromboxane A2 has a role in the development of immune complex glomerulonephritis and that thromboxane synthetase inhibition may be beneficial in attenuating some of the functional and histological changes associated with immune complex glomerulonephritis.