Protective effect of Sobuzoxane (MST-16) against cardiotoxicity of adriamycin (ADM) was inves-tigated in rabbits. ADM (1.0mg/kg) was administered intravenously twice a week for five weeks. MST-16(25mg/kg, p.o.) or ICRF- 187 (25mg/kg, i.p.) was administered 60 or 30 minutes, respectively, before the injection of ADM. The hearts were examined histologically and biochemically at four weeks after accomplishment of administration. In the ADM-administered rabbits, severe vacuolation and loss of myofibrils were observed in the myocardium of the left ventricle by light microscopic observation. In addition, invasion of macrophages and proliferation of fibroblasts were seen in the connective tissue of the myocardium. Electron microscopic observa-tion revealed characteristic alterations of the cardiac myocytes in the ADM treated groups, namely dilation of the sarcoplasmic reticulum and myelin figures derived from mitochondria. These ADM-induced lesions were ameliorated when MST-16 or ICRF-187 was pretreated. However, levels of lipid peroxide and antioxidant enzyme activities of the cardiac muscles were not significantly different from the control values in either experimental group. It is suggested that MST-16 could be a candidate drug for preventing ADM-induced cardiomyopathy.
The relationship of pulmonary fibrosis to development of lung tumors was investigated in Syrian golden hamsters treated with N-methyl-N-nitrosourethane (MNUR). Female animals in groups 1 and 2 received five subcutaneous (sc) injections of 0.6 and 0.2mg, respectively, of the carcinogen, whereas males in group 3 were given a single 0.3mg sc dose. After initiation the animals in each group were maintained, together with controls, without any further treatment for 26 weeks, and then examined for whether proliferative lesions in the lung are secondary to pulmonary inflammatory lesions induced by MNUR. Lung tumors were induced in all hamsters of group 1, but only 56% and 36%, respectively, were accompanied by inflammatory lesions and pulmonary fibrosis. Similar results were also obtained for tumors in group 2 and papillary hyperplasias in the female treated groups, many being observed without any involvement of fibrotic lesions. Glandular metaplasia was observed at high frequency in groups 1-3, but no evidence of a histogenetic link with development of lung tumors was found. A close relation between development of lung tumors and papillary hyperplasias was noted, however. The present study thus suggested that a considerable proportion of lung tumors induced in hamsters by MNUR are independent of toxicity-related changes and presumably due to direct DNA initiating action of the carcinogen.
Modifying effects of KYN-54, a newly synthesized retinoidal butenolide, were investigated on 2-amino- 3-methylimidazo [4, 5-ƒ] quinoline (IQ)-induced carcinogenesis in rats. One hundred and twenty male F344 rats were divided into 4 groups. Starting at 5 weeks of age, rats were fed the basal diet (Groups I and 4) or the experimental diet (0.02% KYN-54) (Groups 2 and 3). At 7 weeks of age, Groups I and 2 were given IQ (0.35m mol/kg body weight, once weekly for 12 weeks) by a intragastric tube. One week after the final IQ intubation, the experimental diet for Group 2 was switched to basal diet. Group 4 was treated as the vehicle control. All rats were sacrificed at the termination (48 weeks after the start of experiment) and 5 rats from each group, which were sacrificed at 12 and 24 weeks. At the termination, sporadic tumors were recognized only in Group I (IQ alone) and Group 2 (IQ+ KYN-54). But no significant differences for each tumor were available between the 2 groups. Furthermore, no statistical differences were recognized for the incidences of aberrant crypt foci in the 2 groups. However, the density of enzyme altered foci of Group 2 was significantly smaller than of Group I (3.21±4.49/cm2 vs. 10.71±9.76/cm2, P<0.05). These results imply that the synthesized butenolide compound has a weakly inhibitory effect on hepatocarcinogenesis in rats.
The influence of the incubation period and the effects of cytochrome P-450 (CYP) inhibitors and inducers on CCl4 toxicity in gerbil hepatocyte cultures were studied. The prolonged incubation of gerbil hepatocyte cultures after seeding was less sensitive to CCl4-induced toxicity and affected the immunostainability of some CYP apoproteins. SKF-525A and chloramphenicol (CPC), which are CYP inhibitors, had significant protective effects on the CCl4-induced T-Chol increase and enzyme leakage. 3-Methylcholanthrene (3-MC) and clofibric acid (CFA) enhanced the CCl4 toxicity, increasing LDH leakage and intracellular contents of TG and T-Chol. 3-MC and CFA treated cells were intensely positive for multi-isoform of CYPs. Ethanol (EtOH) also enhanced the CCl4-induced enzyme leakage and cytoplasmic vacuolation without fatty changes, and increased only CYP2EI staining level within cells. This study revealed that CCl4-induced toxicity in gerbil hepatocytes also depends on some CYP activities.
The effect of hypercholesterolemia on diabetic nephropathy was studied in rats fed with or without cholesterol (CHS) for 112 days after intraperitoneal injection of 50 mg/kg streptozotocin (STZ). Serum cholesterol was increased only in STZ-diabetic and CHS-fed rats, and not in non-diabetic and CHS-fed animals. In the STZ-diabetic and CHS-fed rats, PAS positive mesangial matrix areas were extended with significant increase of collagen IV, laminin, and fibronectin, as compared with STZ-diabetic without CHS feeding rats. The results indicated that hypercholesterolemia promoted the progression of STZ-induced diabetic nephropathy in rats.
To determine the effect of long-term treatment with an angiotensin-converting enzyme (ACE) inhibitor on the morphological change in juxtaglomerular (JG) cells, and the influence of plasma angiotensin II (PAG II) in renin synthesis and secretion in beige rats, an animal model of Chediak-Higashi syndrome, show gradually enlarged and irregularly-shaped JG granules (renin in the granules) according to their degree of maturity. Beige rats were administrated trandolapril, an ACE inhibitor, orally for 4 weeks. Morphological changes in JG cells and renin-angiotensin system function were determined. These rats were examined histologically and ultrastructurally, focussing on morphological changes in JG cells along witg blood pressure, PAG II, and plasma renin activity. Trandolapril reduced systolic blood pressure and decreased PRA remark-ably, but PAG II was highly variable. The most conspicuous histological changes were hypertrophy and hyperplasia of JG cells. Ultrastructurally, JG cells contained an increased number of JG granules of varying morphology. Most JG granules decreased in size and contained smooth materials, but some showed a granular matrix. These results demonstrate that chronic ACE inhibition accelerates synthesis of JG granules including renin and inhibits secretion of renin, but it is not confirmed whether renin synthesis and secretion are affected by PAG II.
Ethinylestradiol (EE) causes testicular atrophy in rats. But the development of EE-induced tes-ticular atrophy and involvement of apoptosis have not been investigated in rats. Male rats aged 10 weeks were dosed orally with EE for 4 weeks and sacrificed sequentially at weeks 2, 3, and 4 of treatment period. The early changes of EE-induced testicular atrophy at week 2 were characterized by cell death of pachytene spermatocytes and round spermatids, exfoliation of round spermatids, and atrophy of Leydig cells. Retention of mature spermatids was also observed at stages IX-XIV. Cell death was seen more frequently in pachytene spermatocytes at stage VII. This cell death was positive for in situ assessment of DNA fragmentation, and had morphological characteristics of apoptosis by electron microscopic observation. Up to week 4, the severity of these changes had been increased. Giant cell formation and vacuolation of Sertoli cells were also observed. These results suggested that EE-induced testicular atrophy is due to apoptosis of spermatogenic cell and exfoliation of spermatids. Apoptosis is thought to play an important role in EE-induced testicular atrophy in rats.
Testicular necrosis induced by human chorionic gonadotrophin (hCG) was examined in rats with respect to the time-course of the histopathologic changes and to the differences in the sensitivity among ages and strains of rats. A single subcutaneous injection of hCG at a dose of 2, 000IU/kg produced focal necrosis of the seminiferous tubules and interstitial tissue in the frontal lower part of the testis of adult F344 rats followed by testicular weight changes. Degeneration or multinucleated giant cells at the seminiferous epithelium or edema and neutrophil infiltration in the interstitium were also observed in the necrotic area 1 day after treatment and thereafter, but no changes were noticed in the upper part of the testis. The necrotic change was induced in F344 rats at the ages of 11 weeks or older, but not at 5 weeks, indicating no susceptibility in the younger age. The sensitivity to hCG was highest in F344/Jcl rats followed by Sprague-Dawley, LEW, WKY, and Wistar rats in descending order. The maximum strain difference in sensitivity was approximately 300 times in hCG dose. These results indicate that hCG induces an acute focal necrosis in the seminiferous tubules that is age-dependent, with a great strain difference in sensitivity.
In order to confirm the relationship between testosterone- administration and glutathione-peroxidase (GSH-PO) in the rat ventral prostate, we have studied the levels of GSH-PO mRNA, GSH-PO activity, and lipid peroxide value in the ventral prostate under the presence or absence of androgen. Male Sprague-Dawley rats were divided into four experimental groups. Group 1 consisted of intact controls. In group 2, rats were sacrificed two days after castration. In groups 3 and 4, rats were administered subcutaneously I mg/animal of testosterone-propionate daily for three or seven days after two days of castration. The prostatic GSH-PO mRNA levels were diminished in the castrated rat ventral prostate but greatly increased by testosterone (Groups 3 and 4). Furthermore, GSH-PO activity was increased and the TBA value was decreased by testosterone-administration (Groups 4). These findings strongly suggest that expression of GSH-PO in the glandular epithelial cells of the rat ventral prostate is considered to be testosterone-dependent.
A study was conducted to determine the mode of action for promoting effect of large amounts of vitamin A (VA) on cell proliferation of thyroid proliferative lesions induced by thiourea (TU) (Mitsumori et at, Cancer Letter 103: 19-31, 1996). Groups of male F344 rats (16/group) received 0.1% TU in water (TU group), 0.1% VA in diet (VA group), both 0.1% TU in water and 0.1% VA in diet (TU+VA group) or distilled water and basal diet (control group) for 4 weeks. Increased weights of thyroids (absolute and relative), liver (absolute and relative) and pituitary (relative), decreased serum T4 levels, and decreased thyroidal iodine uptake, and organification were observed in TU and TU+VA groups, as compared to the control group. Thyroidal iodine organification was also decreased in VA group. However, there were no differences in these parameters between TU and TU+VA groups. No treatment related effects were noted in serum T3 and TSH. No remarkable differences were observed in the histopathological findings of thyroids, liver, and pituitary between TU and TU+VA group, although diffuse follicular cell hyperplasia was induced in these groups. The results in the present study suggest that the enhancement effect of VA on thyroid proliferative lesions may not be attributable to the modification of thyroidal iodine uptake.
The mechanisms of MDP-Lys (L18)-induced arthritis in rats and exacerbating effect of cyclosporin A (CsA) on the arthritis were examined. Consecutive subcutaneous injections of MDP-Lys (L18) for 14 days increased tarsal joint thickness from day 7 up to day 15, with marked recovery after cessation of the treatment. Histological examination, however, revealed multilayered arrangement of synovial lining cells with vesicular cytoplasms and mild neutrophil (NEU) infiltration in the synovial membrane 6 hr after a single injection (early stage). From day 8 (late stage), the lesion progressed in association with chronic signs, such as fibroblast proliferation, infiltration of mononuclear cells and Imphocytes (LYMs), and necrosis of the synovial membrane. However, exudative changes and NEU infiltration were seen throughout the course of the treatment. Rat macrophage-conditioned medium (M∅-CM) stimulated with MDP-Lys (1-18) produced NEU chemotactic factor (NCF), which was also detected in the synovial fluid from dogs with MDP-Lys (L18)-induced arthritis (MIA). The NCF was determined to be one of chemokines by partial purification, and cytokine-induced NEU chemoattractant [CINC, rat interleukin-8 (IL-8)] was detected in the rat M∅-CM. Examination of spleen T cell subsets revealed a decrease in CD8+ cell population in the later stage. Therefore, the chemokine, at least CINC, is thought to contribute to the early and later development of MIA, and the decreased population of CD8+ cells is to the later development. Cyclosporin A (CsA) markedly exacerbated MIA in the later but not early stage, and this was suggested to be caused by its additive effect to decrease CD8+ T cell population with MDP-Lys (L18).
Phospholipidosis-inducing effects of difluorobenzhydrylpiperadine (DFBP) on cultured rat per-itoneal macrophages were studied as compared with those of several amphiphilic drugs. At 24 hr of exposure to DFBP as well as other amphiphilic drugs, intracytoplasmic acid hematein-stained inclusion bodies were dose-dependently produced in macrophages. Electron microscopy showed lamellar inclusion bodies in macrophages exposed to DFBP. Effective concentrations for 30% positivity of treated cells were: 0.43μM/diethylamino-ethoxyhexestrol, 1.9 μM/perhexiline, 2.8μM/quinacrine, 4.3μM/DFBP, 11μM/chlorcyclizine, and 14 μM/ propranolol. Neither almitrine nor aspirin induced the cytoplasmic inclusion bodies.