Splenic hemangiosarcoma in a young sprague-dawley rat.

The present report describes a rare case of spontaneous hemangiosarcoma in a nine-week-old male Sprague-Dawley rat. At necropsy, multiple white nodules of various sizes were observed on and within the enlarged spleen and liver and were histopathologically determined to be composed of spindle- to oval-shaped cells that showed invasive growth without encapsulation and were arranged solidly but partially in whorls or faint alveolar patterns with vascular-like spaces containing small clefts or erythrocytes in the tumor mass. Immunohistochemical analysis revealed that most of the tumor cells were strongly positive for vimentin, von Willebrand factor (vWF) and CD34 but negative for podoplanin. In addition, electron microscopic examination revealed the presence of Weibel-Palade bodies in the cytoplasm of the tumor cells. Based on these findings, this case was diagnosed as a hemangiosarcoma. The splenic masses were larger than the hepatic ones, with tumor cells mainly observed at periportal regions with tumor embolism in the liver, suggesting that primary hemangiosarcoma initially developed in the spleen before metastasizing.

Myocardial necrosis related to hydrochlorothiazide-induced hypokalemia in cynomolgus monkeys.

Myocardial necrosis is a serious adverse effect that results from the administration of some medications; therefore, when it is observed during preclinical studies it becomes a major drug development concern. Although data from preclinical monkey studies are generally extrapolated to predict effects in humans, few reports have described any mechanism that might explain the occurrence of myocardial necrosis. For this reason, we examined the association between hypokalemia and myocardial necrosis in monkeys. Four female cynomolgus monkeys (Macaca fascicularis) were treated with 50 mg/kg/day hydrochlorothiazide (a thiazide diuretic used for antihypertensive therapy) for 1 or 2 weeks. Clinical, hematological, plasma biochemical, and pathological examinations were conducted. Two animals were kept in a hypokalemic state from day 3 of dosing on, and their mean plasma potassium levels were 2.52 +/- 0.24 and 2.60 +/- 0.24 mmol/l. These animals were necropsied after 1 week of dosing due to an aggravated general condition. A flattened T-wave was noted during electrocardiography. A transient increase in plasma cardiac-specific troponin-I and multifocal myocardial necrosis also occurred. The rest of the animals were occasionally hypokalemic, with mean plasma potassium levels of 3.13 +/- 0.31 or 2.96 +/- 0.30 mmol/l. These animals were necropsied after 2 weeks of dosing. One animal showed evidence of focal myocardial necrosis and a transient increase in plasma cardiac-specific troponin-I. These data suggest that the severe hypokalemia induced by hydrochlorothiazide is likely to be associated with myocardial necrosis in monkeys.

YM440, a novel hypoglycemic agent, protects against nephropathy in Zucker fatty rats via plasma triglyceride reduction.

The novel hypoglycemic agent, YM440 ((Z)-1,4-bis{4-[(3,5-dioxo-1,2,4-oxadiazolidin-2-yl) methyl] phenoxy}but-2-ene) is a ligand of the peroxisome proliferator-activated receptor, (PPAR) gamma. YM440 has been shown to counteract insulin resistance in diabetic rodent models. However, it is not clear whether this compound has a significant effect on hyperlipidemia in vivo. Hyperlipidemia has been reported to be a risk factor for the early development of renal disease. The aim of this study is to examine the effects of chronic treatment with YM440 on hyperlipidemia and renal injury in obese Zucker fatty (ZF) rats. Treatment of 8-week-old ZF rats with YM440 (100 mg/kg/day) for 16 weeks decreased plasma triglyceride and cholesterol concentrations. YM440 markedly reduced the rate of progression of both albuminuria and proteinuria. YM440 normalized urinary N-acetyl-beta-D-glucosaminidase (NAG) activity, which is a marker for renal proximal tubular damage, and ameliorated the rise in systolic blood pressure compared to the vehicle control. YM440 also blocked the development of nephromegaly. Histological analyses revealed that both glomerular area expansion and tubular cast accumulation gradually lessened in YM440-treated ZF rats. Regression analyses between the plasma triglyceride levels and the renal parameters (urinary protein excretion and albumin excretion) indicated that the renal parameters correlated positively with the plasma triglyceride levels. In conclusion, the hypolipidemic effects of YM440 prevent renal injury in ZF rats. YM440 might be useful for preventing the early development of diabetic nephropathy in subjects with type 2 diabetes by ameliorating metabolic control problems.

Changes in submaxillary gland gene expression in F344 rats by multiple dosing of theophylline.

Multiple exposure to theophylline, a phosphodiesterase (PDE) inhibitor, induces acinar hypertrophy in the salivary gland. This study examined the effect of theophylline on the gene expression of secretory proteins and phosphodiesterases in the submaxillary gland. Male F344 rats received saline or theophylline (50 mg/kg) intraperitoneally for 4 days. The gene expressions for the secretory protein, cystatin S (CysS), and PDE subfamilies 3A and 4D in the submaxillary gland were quantified using RT-PCR. Theophylline exposure resulted in a sustained increase in mRNA expression for CysS and PDE3A, but PDE4D gene expression was unchanged. Our results suggest that submaxillary hypertrophy is primarily caused by the enhanced transcription of CysS, and that the transcription of each PDE subfamily gene is regulated differently.

Nitrofurazone-induced gene expressions in rat hepatocytes and their modification by N-acetylcysteine.

The antibiotic nitrofurazone (NF) at a subtoxic dose has been shown to increase hepatocyte DNA synthesis with no preceding cell damage or necrosis. This was suppressed by concomitant administration of the antioxidant N-acetylcysteine (NAC), which suggests that free radical production is involved in the process. In this study, male F344 rats were given a single oral subtoxic dose of NF to investigate the changes in genes implicated in hepatocyte proliferation between 1 and 20h postdose by real-time PCR. Some rats were also given NAC to examine the involvement of free radicals. There were transient and sequential increases in mRNA levels of c-myc and c-jun shortly after the administration, followed by tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-alpha (TGF-alpha), c-Ha-ras, and cyclin E. The increases were blocked by concomitant administration of NAC. In contrast, there were no NF-specific increases in c-fos, hepatocyte growth factor, epidermal growth factor or cyclin D1 mRNAs. These results indicate that the induction of hepatocyte proliferation by NF is triggered by free radicals, with a pathway involving increases in c-jun, c-myc, TNF-alpha, TGF-alpha, c-Ha-ras, and cyclin E. The results also indicate that NF-induced proliferation resembles that of other mitogens.

Temporal reduction in size of salivary acinus in rats induced by theophylline.

Repeated administration of theophylline, a phosphodiesterase inhibitor, induces the enlargement of the salivary glands in rats. Time-course changes after a single administration of theophylline were examined in the salivary glands, including phosphodiesterase enzyme activity, and the expression of aquaporin 5 (AQP5), a water channel. We also examined the contribution of beta-adrenergic receptors to theophylline-induced salivary changes. Male F344 rats were given 50 mg/kg of theophylline intraperitoneally either alone or concurrently with a 10 mg/kg subcutaneous injection of propranolol. After treatment with theophylline alone, the weight and histology of the submaxillary and parotid glands were examined. Phosphodiesterase activity and AQP5 were detected by enzyme- and immuno-histochemistry, respectively. At 4 hours, 8 hours, or both, organ weights were decreased with depletion of secretory vesicles in the acinar cells. In the submaxillary glands, reduced activity of phosphodiesterase and increased expression of AQP5 in the intercalated ducts were observed at 4 hours. When co-administered, propranolol partially abolished theophylline-induced glandular reduction. These results suggest that the theophylline-induced transient reduction in size of the salivary glands is attributable not only to phosphodiesterase inhibition but also to beta-adrenergic receptor activation and that the intercalated ducts in submaxillary glands play a role in the production of saliva.

Immunohistochemical study on inducible type of nitric oxide (iNOS), basic fibroblast growth factor (bFGF) and tumor growth factor-beta1 (TGF-beta1) in arteritis induced in rats by fenoldopam and theophylline, vasodilators.

Arteritis induced in rats by vasodilators, fenoldopam and theophylline, was examined immunohistochemically for expressions of inducible type of nitric oxide synthase (iNOS), basic fibroblast growth factor (bFGF) and tumor growth factor-beta1 (TGF-beta1). Rats were administered fenoldopam for 24 hours by intravenous infusion with or without following repeated daily oral administrations of theophylline. Irrespective of theophylline administration, iNOS antigens were remarkably abundant in ED-1-positive cells on day 5 and 8 post-fenoldopam-infusion (DPI); bFGF antigens were remarkably abundant in ED-1-positive cells on 1 and 3 DPI; TGF-beta1 antigens were observed in ED-1-positive cells on and after 5 DPI. These results suggest that the peak expression of iNOS antigen was followed by that of bFGF antigen, and bFGF may have a suppressive effect on iNOS expression in these rat arteritis models. On the other hand, TGF-beta1 was not considered to have a suppressive effect on iNOS expression in these models.