[The diagnosis of a mutation of the insulin receptor by non-radioisotropical RT-PCR-SSCP analysis]

We evaluated a 24 years old diabetes woman with type A insulin resistant (patient "Yakushima") who had some typical symptoms as acanthosis nigricans, hirsutism and virilization. Insulin binding to the patient's erythrocytes was significantly decreased to about 30% of the normal control. In order to determine the mutation of the insulin receptor, we used for reverse transcript-polymerase chain reaction-single strand conformation polymorphism (RT-PCR-SSCP) analysis without using radiolabeled materials. We also analysed the nucleotide sequence with non-isotropical probe. Our results suggested that the mutation was heterozygous, and the patient had a new missense mutation substituted Asn461 for Thr461 in the alpha-subunit.

Serum pepsinogen as a new marker for gastric carcinoma among young adults. Research Group on Prevention of Gastric Carcinoma among Young Adults

BACKGROUND

Gastric carcinoma is relatively uncommon in Japan among persons younger than 40 years of age, but its prognosis is not favorable and it affects young adults in their most productive years. This study was performed to evaluate the validity of serum pepsinogen as a new marker for gastric carcinoma among Japanese younger than 40 years of age.

METHODS

Data and sera were collected from the patients (108 patients younger than 40 years of age with gastric carcinoma from nine hospitals in the Kanto-Shin'etsu area in Japan) and from the control subjects (108 hospital control subjects and 108 screening control subjects) whose sex and age (within 4 years) were matched. Pepsinogen I and pepsinogen II values were measured and compared between patients and control subjects by paired t test. Sensitivities and specificities when criteria were defined by pepsinogen I, pepsinogen II, and pepsinogen I/II ratio were calculated.

RESULTS

The pepsinogen I and pepsinogen II levels among patients were higher and the pepsinogen I/II ratio among patients was lower than among control subjects. When a pepsinogen II level higher than 14.8 ng/ml was considered positive, the test showed high sensitivity (83.3% for total gastric carcinoma and 85.0% for early gastric carcinoma) and high specificity (76.9% for hospital control subjects and 75.0% for screening control subjects). Similar degrees of sensitivity and specificity were obtained with the pepsinogen I/II ratio.

CONCLUSIONS

These results suggest that a high pepsinogen II level combined with a low pepsinogen I/II ratio may be a useful screening test for gastric carcinoma in a young population at high risk for gastric carcinoma. This impression should be confirmed by a more extensive field trial to determine whether performance of these assays promotes early diagnosis of gastric carcinoma.

Cortical control of saccade in normal and schizophrenic subjects: a PET study using a task-evoked rCBF paradigm

In this study, positron emission tomography (PET) was used to evaluate cortical control of saccades. Regional cerebral blood flow (rCBF) patterns demonstrated by 15O water PET during saccadic task performance were tested in 13 normal volunteers and 20 ICD-9 schizo phrenics (10 unmedicated and 10 medicated). The following 3 saccadic tasks, which were controlled for sensory input and oculomotor output, were applied: (1) reflexive saccade = visually guided saccade, (2) volitional saccade = visually guided saccade with distracting stimuli, and (3) memory guided saccade. Schizophrenics lacked the frontal eye field (FEF) activation during every saccadic task. The left dorsolateral prefrontal cortex (DLPFC) was activated during volitional saccade only in normal controls. The rCBF of posterior parietal cortex increased in parallel with that in the DLPFC. These findings suggest functional hypofrontality in schizophrenia and the left DLPFC-PPC's crucial role in saccade against distracting stimuli and its dysfunction in the disease.

Effects of oxygen free radical scavengers on uranium-induced acute renal failure in rats

Study was made to determine whether oxygen free radicals mediate uranium-induced acute renal failure (ARF). Superoxide dismutase (SOD), a superoxide anion scavenger, did not prevent uranium acetate (UA) (5 mg/kg, i.v.)-induced renal injury 48 h after injection. In contrast, dimethylthiourea (DMTU), a hydroxyl radical scavenger, significantly attenuated UA-induced rise in serum creatinine concentration (1.11 +/- 0.05 (DMTU) vs. 1.40 +/- 0.06 mg/dl (control), p < .05), and tubular necrosis. Dimethyl sulfoxide (DMSO), a hydroxyl radical scavenger, decreased UA-induced tubular damage. UA injection caused no increase in renal cortical malondialdehyde (MDA) content. DMTU and DMSO did not modify intrarenal MDA content. UA administration brought about significant increase in plasma renin activity but not in renal cortical renin content. Treatment with DMTU and DMSO had no effect on plasma renin activity or intrarenal renin content. It follows from these findings that DMTU and DMSO may attenuate UA-induced renal injury. Such a protective effect would not be mediated through modulation of lipid peroxidation or renin activity.

[Effects of estrogen and progestin on platelet-activating factor acetylhydrolase]

Platelet-activating factor (PAF) is one of the potent proinflammatory agents and is associated with a number of human diseases, including asthma, endotoxin shock and cardiovascular diseases. Additionally, plasma PAF acetylhydrolase (PAF-AH) activity to inactivate PAF is regulated by hormones. In this study, we elucidated the effects of estrogen and progestin on plasma PAF-AH and also the effects of PAF on rat tissues to investigate the mechanisms involved in the thrombotic episode. Plasma PAF-AH activity in female adult rats treated with 17 alpha-ethynylestradiol (50 micrograms/kg, 5 days) was decreased by 50%. However, medroxyprogesterone (50 mg/kg, 5 days) increased the enzyme activity by 50%. When PAF (5 to 60 nmol/kg) was injected intravenously into non-treated female adult rats, 80% of the animals died at 20 nmol/kg of PAF. Macroscopic findings showed hemorrhage, hyperemia and congestion in the lungs and heart, and necrosis-like change in the gastrointestines. Microscopically, thrombus was observed in the lungs and heart. When PAF was administered to female adult rats pretreated with sex steroid hormones, the mortality of the rats with low plasma PAF-AH activity caused by estrogen was increased, but decreased in the animals with high enzyme activity caused by progestin. These findings suggest that the imbalance between PAF and plasma PAF-AH is one of the mechanisms involved in the thrombotic episode, and estrogen and progestin are related to the event by regulating the plasma PAF-AH activity.

A 3-Mb physical map of the chromosome region 8p21.3-p22, including a 600-kb region commonly deleted in human hepatocellular carcinoma, colorectal cancer, and non-small cell lung cancer

To isolate a putative tumor suppressor gene(s), we have constructed a physical map and a detailed deletion map of chromosome region 8p21.3-p22, where loss of heterozygosity (LOH) has been frequently seen in human hepatocellular carcinomas (HCC), colorectal cancers (CRC), and non-small cell lung cancers (NSCLC). The smallest commonly deleted region at 8p21.3-p22 in HCC and CRC was between the loci defined by C18-245 and C18-2644; in NSCLC, a region between C18-1051 and C18-2644 was commonly deleted. A contiguous physical map of 12 cosmid markers in the 8p21.3-p22 region was constructed by means of multi-color fluorescence in situ hybridization (FISH) and pulsed-field gel electrophoresis (PFGE). On the basis of this physical map, which spans roughly 3.1 Mb, the estimated sizes of the commonly deleted regions were at most 1.2 Mb in HCC and CRC and 0.6 Mb in NSCLC. As four of the 12 physically ordered markers are located within the 0.6 Mb region commonly deleted in all three tumor types, nearly one fourth to one fifth of the target region has already been covered with cosmid inserts.

Rod-like intracytoplasmic inclusions in large neurons of the caudate nucleus: frequent appearance in myotonic dystrophy

Brain autopsy materials from 5 patients diagnosed clinicopathologically as having myotonic dystrophy (MyD) were studied. All of the cases showed many rod-like intracytoplasmic inclusions, which have never been reported in the disease, in the large neurons of the caudate nucleus. The rod-like inclusions were observed in the cytoplasm near the nucleus, and showed eosinophilic staining with HE, blue with PTAH, red with Masson's trichrome, and blue with toluidine blue. Electron microscopically, the inclusions had an internal structure composed of parallel beaded dark filaments and clear spaces. In transverse section, the inclusions showed tetragonal arrays of filaments. These histological characteristics of the inclusions were similar to those of inclusions reported previously in the same location in various disorders, showing increasing incidence with aging. Quantitative investigation on the 5 patients and 24 control subjects revealed that the number of neurons containing the inclusion in the caudate nucleus of MyD patients was about twice as many as the control subjects, and that the occurrence rate of the inclusion body to the large neurons in the caudate nucleus in MyD was far higher than that of the controls. The finding indicates that the inclusion body is important for the diagnosis of the disease, and may have a close relationship with the neurological symptoms and pathogenesis of the disease.

[Distribution and frequency of gastric cancer at the para-cardiac region and fornix]

To clarify the distribution and frequency of gastric cancer in the upper third of the stomach, especially in the para-cardiac region and fornix, we reviewed 634 lesions of all gastric cancers in any location in the University Hospital of Tsukuba University from April 1985 to March 1992. The para-cardiac region was defined as a circular area of 6 cm in diameter around the cardia. We found 56 lesions (8.8%) in the para-cardiac region, almost all of which were concentrated in the distal half of the para-cardiac region, and only three of which (0.47%) were in the fornix. Cancer in the upper third of the stomach tended to occur predominantly in aged male patients, and histologically most of them were classified as having differentiated adenocarcinoma. Since the percentage of advanced cancer at the para-cardiac region was much higher than at any other location, we should be careful to obtain double-contrast images of sufficient quality during the upper gastrointestinal examinations and not to overlook subtle changes in this region during the interpretation of films.

Glutamate release in the gerbil hippocampus after middle cerebral artery occlusion

In a modified version of the unilateral middle cerebral artery occlusion (MCAO) model in gerbils, both sides of hippocampus are spared from direct ischaemic insult. Using this newly employed left MCAO model in gerbils, we investigated the concentrations of extracellular amino acids in the left hippocampus by microdialysis and histological changes in both sides of hippocampus one month after ischaemia. The concentrations of glutamate and aspartate were significantly increased by more than 3.5 times basal levels after MCAO. Glutamate maintained this peak level for 40 to 120 min after the onset of ischaemia. However, hippocampal neurones were well preserved one month after MCAO. While the exact mechanism of the survival of hippocampal neurones remains to be elucidated, we suggest it may be crucial that the hippocampus be protected from ischaemic insult.

Molecular mechanism of cibenzoline-induced anticholinergic action in single atrial myocytes: comparison with effect of disopyramide

The anticholinergic effects of cibenzoline were examined and compared with those of disopyramide in atrial myocytes isolated from guinea pig heart. The tight-seal whole-cell voltage clamp technique was performed with a patch pipette filled with guanosine-5'-triphosphate (GTP) or guanosine-5'-O-(3-thiotriphosphate) (GTP gamma S). In GTP-loaded cells, both acetylcholine (ACh) and adenosine (Ado) induced a specific K channel current through GTP-binding proteins by binding to the muscarinic and Ado receptors, respectively. Both cibenzoline and disopyramide suppressed the ACh-induced K current effectively in a concentration-dependent manner. The concentrations for half-maximal inhibition of the current (EC50) caused by cibenzoline and disopyramide were 8 and 3 microM, respectively. In GTP gamma S-loaded cells, the K current was irreversibly activated because GTP binding proteins were directly elicited by GTP gamma S. Cibenzoline effectively caused a decrease in the GTP gamma S-induced K current, whereas the extent of disopyramide action on the GTP gamma S-induced K current was much less. Cibenzoline also caused significant inhibition of Ado-induced K current in GTP-loaded cells. However, the action of disopyramide was less effective in inhibiting Ado-induced K current. These results indicate that cibenzoline has less potent anticholinergic effects than disopyramide in atrial myocytes. In addition, cibenzoline effectively inhibits the muscarinic K channel itself and/or GTP-binding proteins coupled to the channel, whereas the effect of disopyramide is attributed mainly to blockade of muscarinic receptors. These findings provide novel understanding of the molecular mechanism of anticholinergic action of cibenzoline.

The recognition of cancer-associated fucosylated antigens in colorectal cancer by a novel monoclonal antibody, YB-2

A monoclonal antibody, YB-2, which has a novel epitope for fucosylated antigens and shows cross-reactivity with Y/Leb/H type 2 antigens, was used in an immunohistochemical study of human neoplastic and normal colorectal tissues. Of 64 colorectal cancers, 59 (92.2%) were stained by the YB-2 antibody; however, only 3 (12.0%) of 25 samples of normal colon mucosa and 13 (50.0%) of 26 adenomas expressed the antigens recognized by YB-2. Clinicopathologically, the YB-2-negative colon cancers were exclusively in Dukes stage A. These results indicate that the monoclonal antibody, YB-2, could detect cancer-associated antigens, and the degree of YB-2-reacted antigen expression might be correlated with the progression of colorectal carcinogenesis.

[A case of mediastinal neurilemmoma originating from the intrathoracic vagal nerve]

A case of neurilemmoma originating from the intrathoracic vagal nerve was reported. An asymptomatic 51-year-old man was admitted because of a mass shadow on chest roentgenograms. Under the possible diagnosis of benign bronchogenic cyst, right thoracotomy was carried out. An encapsulated solid tumor originating from the right vagal nerve was found in the site distal to the branching point of recurrent nerve. The tumor was removed by transection of the vagal nerve. Postoperative clinical course was uneventful except the transient sinus tachycardia. The pathological diagnosis was neurilemmoma. Mediastinal neurilemmoma originating from the vagal nerve is rare. To our knowledge, only 29 cases are reported in the Japanese literatures.

Evaluation of malignant grade of salivary gland tumors: studies by cytofluorometric nuclear DNA analysis, histochemistry for nucleolar organizer regions and immunohistochemistry for p53

Investigations were carried out in 109 surgically resected salivary gland tumors, 46 adenomas and 63 carcinomas for nuclear DNA content by cytofluorometry, nucleolar organizer regions (AgNOR) by histochemistry and nuclear p53 accumulation by immunohistochemistry. The mean nuclear DNA content and the incidence of aneuploidy as well as the mean number of the AgNOR in carcinomas were significantly higher than those in adenomas. In the DNA histogram pattern, the aneuploidy frequently appeared in high grade carcinoma groups (adenocarcinoma, salivary duct carcinoma, carcinoma in pleomorphic adenoma and oncocytic carcinoma). Immunohistochemical nuclear p53 accumulation was observed in 15 tumors, of which ten showed DNA aneuploidy. In high grade carcinomas, DNA aneuploidy was closely related to p53 immunoreactivity. This study revealed that combined cytofluorometric nuclear DNA analysis, histochemical AgNOR count and immunoreactivity for p53 might be quite useful for evaluating the malignant grade of salivary gland tumors.

Nephrogenic diabetes insipidus associated with bilateral ureteral obstruction

Nephrogenic diabetes insipidus associated with ureteral obstruction is rare. We report a case of nephrogenic diabetes insipidus associated with ureteral obstruction caused by ileal leiomyosarcoma in a 32-year-old man. The treatment with trichlorothiazide and diclofenac sodium reduced urine output from 8 L/day to 4 L/day. Six months after nephrostomy, urine output decreased to 2.5 L/day without any drug administration. This case suggests that ureteral obstruction may cause an increase in urine output to 8 L/day and that surgical treatment for ureteral obstruction is effective in reducing urine output in nephrogenic diabetes insipidus patients with ureteral obstruction.

[Suppressive effect of oxatomide on the induction of IL2 responsiveness by DF-stimulated lymphocytes from patients with bronchial asthma]

Oxatomide is an anti-allergic agent having an anti-histamine effect, and has been widely used for clinical purposes. The effect of oxatomide-treatment on the induction of IL2 responsiveness by Df-stimulated lymphocytes was studied in patients with bronchial asthma. Oxatomide alone has almost no effect on lymphocyte activation. Patient's lymphocytes pretreated with 2 to 2000 ng/ml doses of oxatomides for 24 to 48 hours failed to produce Df-induced IL2 responsiveness in a dose-dependent manner. The target cells for oxatomide's suppressive effect were antigen-presenting cells such as macrophages and dendritic cells rather than responder T cells. PPD-induced IL2 responsiveness was also suppressed by the treatment, but the Con A-induced response was not. The results suggest that oxatomide has a slight immunosuppressive capability to block the induction of IL2 responsiveness by Df-stimulated patient's lymphocytes, resulting in the decreased production of such lymphokines as IL2, IL3, IL4, IL5, in a lymphokine cascade of allergic responses, in addition to inhibition of the degranulation and activation of inflammatory cells such as mast cells/basophils and eosinophils.

Expression of proliferating cell nuclear antigen in invasive ductal carcinoma of the breast

Formalin-fixed, paraffin-embedded sections from 92 breast cancers (invasive ductal carcinomas) were immunostained with a monoclonal antibody against proliferating cell nuclear antigen (PCNA). The labeling index of PCNA ranged widely from 2 to 76 (mean 24.8)%. The labeling index was classified into three groups: low (< 25%), intermediate (25-50%), high proliferation (> 50%). Younger patients seemed to have a higher labeling index than older ones. The labeling index for tumors < or = 2 cm was lower than that of tumors larger than 2 cm. The labeling index in patients with high estrogen receptor (ER) levels (> 100 fmol/mg cytosol protein) was significantly lower than that in patients with low ER levels (< 10 fmol/mg cytosol protein). In relation to histological type, the labeling index of scirrhous carcinoma was significantly lower than that of papillotubular carcinoma or solid-tubular carcinoma. The high proliferating group had a significantly worse overall survival rate than the low proliferating group. Labeling index was shown to be a possible prognostic indicator.

How extensive should lymph node dissection be for cancer of the thoracic esophagus?

From 1985 to 1992, 171 patients with cancer of the thoracic esophagus underwent esophagectomy with systematic dissection of regional lymph nodes including cervical nodes. The hospital mortality rate was 5.3%. The dissected nodes were classified into four groups: the deep cervical (C), upper mediastinal and cervical paratracheal (U), middle and lower mediastinal (L), and upper perigastric (G) groups. The U group mainly consisted of nodes beside the recurrent laryngeal nerves. The phase of cancer infiltration of lymph nodes was evaluated by the total number and the distribution of involved nodes. Of cases with nodal involvement, only 37% were in the late phase, in which more than seven nodes or in which the U, L, and G groups were all involved. Of cases in the earliest phase in which only one node was involved, 93% had either the U or G group involved. The C group of nodes was infrequently involved until the late phase. Cancer had metastasized to the U and G groups across a considerable anatomic distance even in earlier phases. Outcomes of the cases with nodal involvement not in the late phase were satisfactory; the cumulative survival was 60% at 3 years and 54% at 5 years. Systematic nodal dissection would benefit even cases with nodal involvement, unless the disease is in the late phase. Nodes beside the recurrent nerves and upper perigastric nodes should be dissected with higher priority, though they are located anatomically distant.

Cytodiagnostic clues to primary retinoblastoma based on cytologic and histologic correlates of 39 enucleated eyes

In 39 cases undergoing ocular enucleation, cytologic characteristics of primary intraocular retinoblastomas were examined in relation to histologic findings. Retinoblastoma cells occurred singly or in clusters within the associated necrotic debris. Calcific deposits were present in both cytologic and histologic specimens. Portions of capillaries with perivascular tumor infiltrates were identified as pseudorosettes. Wright rosettes were occasionally seen in poorly differentiated retinoblastomas. Flexner-Wintersteiner rosettes were uncommon; however, "mirror ball-like" clusters in cytologic materials correlated well with the rosettes and were a diagnostic clue. Cytomorphologically, the tumor cells could be divided into two types that reflected their histologic grading of differentiation. These findings are cytodiagnostic clues to the presence of retinoblastomas and can be helpful in the cytologic diagnosis.

A ruptured thymic branch aneurysm mimicking a ruptured aortic aneurysm, with associated bronchial artery aneurysms: report of a case

A 57-year-old woman who went into shock following an acute left hemothorax was operated on after stabilization under the diagnosis of a ruptured aortic aneurysm. A left fifth intercostal thoracotomy was done which revealed approximately 500 ml of bloody effusion in the extrapleural space and 2,000 g of clotted blood in the pleural cavity. While the aneurysm was initially thought to have originated in the isthmic or descending aorta, intraoperative findings revealed a swollen hematomatous thymus adherent to the aorta. A ruptured thymic branch aneurysm, 3 cm in diameter, was subsequently found in the resected hematomatous thymus. Histological examination also revealed several small aneurysms in the tortured bronchial arteries. Postoperative angiography showed a saccular aneurysm, 1.5 cm in diameter, and several smaller aneurysms in the bronchial artery of the left lung. The aneurysm was successfully treated by a transcatheter arterial embolization, and the patient has had no further symptoms since then. To our knowledge, there has been no other case of a ruptured thymic artery aneurysm reported in the literature, and only a few cases of bronchial artery aneurysms have been documented.

Isolation and properties of a protein complex containing flagellar movement-initiating phosphoprotein from testes of a white salmon

Phosphorylation of a tyrosine residue within a 15-kDa protein has been found to play a role in the initiation of flagellar movement of quiescent spermatozoa of the rainbow trout, Salmo gairdneri [Morisawa & Hayashi (1986) Biomed. Res. 6, 181-184; Hayashi et al. (1987) J. Biol. Chem. 262, 16692-16698]. In order to find a more accessible source of the 15-kDa protein for biochemical studies, phosphorylation of proteins was studied in other organs from other species. Cell-free extracts from spermatozoa and testes of Salmonidae were prepared and all catalyzed the cAMP-dependent, Mg(2+)-requiring, but Ca(2+)-independent phosphorylation of the 15-kDa proteins. Protein from the testes of a white salmon, Oncorhynchus keta, was isolated by conventional purification methods. The 15-kDa protein in the cell-free extract was found to be complexed with several other proteins such that the 15-kDa protein and its phosphorylating activity were copurified. Isolation of a sufficient amount of the complex for the preparation of antibodies against the various constituents is now possible.

Characteristics of Ki1769, a novel vasodilator, in isolated rat aorta

The vasorelaxant mechanism of a newly synthesized vasodilator, Ki1769 [N-cyano-N'-(2-phenethyl)-3-pyridinecarboximidamide], was studied in isolated rat aorta in comparison with cromakalim. Ki1769 (10(-8)-10(-5) M) and cromakalim (10(-8)-10(-5) M) produced a concentration-dependent relaxation and the EC50 values for Ki1769 and cromakalim were (8.60 +/- 1.90) x 10(-7) M and (1.36 +/- 0.18) x 10(-7) M, respectively. Ki1769- and cromakalim-induced relaxations were competitively antagonized by glibenclamide with pA2 values of 6.83 and 6.93, respectively. Charybdotoxin, apamine, atropine, propranolol and indomethacin did not affect the Ki1769-induced relaxation. An increase in 86Rb efflux was induced by Ki1769. Glibenclamide attenuated the increase in 86Rb efflux produced by Ki1769. These results suggest that the vasorelaxant effect of Ki1769 is based on the glibenclamide-sensitive K channel-opening action.

Cloning of the Saccharomyces cerevisiae gene whose overexpression overcomes the effects of HM-1 killer toxin, which inhibits beta-glucan synthesis

A gene whose overexpression can endow Saccharomyces cerevisiae cells with resistance to HM-1 killer toxin was cloned from an S. cerevisiae genomic library. This gene, designated HKR1 (Hansenula mrakii killer toxin-resistant gene 1), contains a 5.4-kb open reading frame. The predicted amino acid sequence of the protein specified by HKR1 indicates that the protein consists of 1,802 amino acids and is very rich in serine and threonine, which could serve as O-glycosylation sites. The protein also contains two hydrophobic domains at the N-terminal end and in the C-terminal half, which could function as a signal peptide and transmembrane domain, respectively. Hkr1p is found to contain an EF hand motif of the calcium-binding consensus sequence in the C-terminal cytoplasmic domain. Thus, Hkr1p is expected to be a calcium-binding, glycosylated type I membrane protein. Southern and Northern (RNA) analyses demonstrated that there is a single copy of the HKR1 gene in the S. cerevisiae genome, and the transcriptional level of HKR1 is extremely low. Gene disruption followed by tetrad analysis showed that HKR1 is an essential gene. Overexpression of the truncated HKR1 encoding the C-terminal half of Hkr1p made the cells more resistant to HM-1 killer toxin than the full-length HKR1 did, demonstrating that the C-terminal half of Hkr1p is essential for overcoming the effect of HM-1 killer toxin. Furthermore, overexpression of HKR1 increased the beta-glucan content in the cell wall without affecting in vitro beta-glucan synthase activity, suggesting that HKR1 regulates beta-glucan synthesis in vivo.

Mechanisms for protective effects of free radical scavengers on gentamicin-mediated nephropathy in rats

Studies were performed to examine the mechanisms for the protective effects of free radical scavengers on gentamicin (GM)-mediated nephropathy. Administration of GM at 40 mg/kg sc for 13 days to rats induced a significant reduction in renal blood flow (RBF) and inulin clearance (CIn) as well as marked tubular damage. A significant reduction in urinary guanosine 3',5'-cyclic monophosphate (cGMP) excretion and a significant increase in renal cortical renin and endothelin-1 contents were also observed in GM-mediated nephropathy. Superoxide dismutase (SOD) or dimethylthiourea (DMTU) significantly lessened the GM-induced decrement in CIn. The SOD-induced increase in glomerular filtration rate was associated with a marked improvement in RBF, an increase in urinary cGMP excretion, and a decrease in renal renin and endothelin-1 content. SOD did not attenuate the tubular damage. In contrast, DMTU significantly reduced the tubular damage and lipid peroxidation, but it did not affect renal hemodynamics and vasoactive substances. Neither SOD nor DMTU affected the renal cortical GM content in GM-treated rats. These results suggest that 1) both SOD and DMTU have protective effects on GM-mediated nephropathy, 2) the mechanisms for the protective effects differ for SOD and DMTU, and 3) superoxide anions play a critical role in GM-induced renal vasoconstriction.