Methylmercury poisoning in common marmosets--a study of selective vulnerability within the cerebral cortex

Neuropathological lesions found in chronic human Minamata disease tend to be localized in the calcarine cortex of occipital lobes, the pre- and postcentral lobuli, and the temporal gyri. The mechanism for the selective vulnerability is still not clear, though several hypotheses have been proposed. One hypothesis is vascular and postulates that the lesions are the result of ischemia secondary to compression of sulcal arteries from methylmercury-induced cerebral edema. To test this hypothesis, we studied common marmosets because the cerebrum of marmosets has 2 distinct deep sulci, the calcarine and Sylvian fissures. MRI analysis, mercury assays of tissue specimens, histologic and histochemical studies of the brain are reported and discussed. Brains sacrificed early after exposure to methylmercury showed high contents of methylmercury and edema of the cerebral white matter. These results may explain the selective cortical degeneration along the deep cerebral fissures or sulci.

[A patient with neuroborreliosis presenting gadolinium-enhanced MRI lesions in bilateral facial nerves]

We report a 33-year-old man with bilateral facial paralysis due to neuroborreliosis. About three weeks after rhinorrhea and fever lasting four days, he noticed fatigue in the legs and paresthesia in all four extremities. Another week later, he developed paresthesia in his tongue and bilateral facial muscle weakness, and was admitted to our hospital. On admission, neurological examination revealed moderate bilateral facial muscle weakness, mild paresthesia in the tongue and four extremities, and decreased Achilles tendon reflex bilaterally. Mild pleocytosis and increased protein were found in the cerebrospinal fluid (CSF). IgM antibodies that reacted with the antigens of Borrelia garinii and Borrelia afzelii were found in his serum. Clinically and serologically, he was thus diagnosed as having neuroborreliosis. Brain MRI revealed gadolinium-enhanced lesions of the bilateral facial nerves in the facial nerve canal portion. After three weeks of treatment with 100 mg/day doxycycline and 2 g/day ceftriaxone sodium, his symptoms and CSF abnormalities were rapidly improved. Although facial nerve paralysis is a major symptom of neuroborreliosis, the present report is the first to detect the inflammatory lesions of the facial nerves in the facial nerve canal portion by MRI.

[Lymphedema after radical prostatectomy: a case report]

We report a case of intractable lymphedema of the left leg following radical prostatectomy. The 69-year-old male patient complained of difficulty walking, caused by severe lymphedema. Intraarterial autologous lymphocyte transfusion therapy was performed because of failure of conventional conservative therapy, and the leg edema resolved almost completely. However, the treatment did not improve the penoscrotal edema necessitating excision of the edema and skin graft in a separate procedure. The post-operative course was excellent and the patient's performance status improved to 1 from 3.

Glomerular endothelial cells are maintained by vascular endothelial growth factor in the adult kidney

Vascular endothelial growth factor (VEGF) is known to maintain endothelial cells of immature vessels and is constitutively expressed in the kidney from the embryo to adult. We tested the hypothesis that VEGF activity is needed to maintain glomerular endothelial cells in the adult. Neutralizing antibody to VEGF165 was intraperitoneally administered to mice for 3 days to strongly suppress its intrinsic activity. On the fourth day, mice were sacrificed and tissues were examined by light and electron microscopies. Vascular casts of renal vessels were observed by a scanning electron microscopy. Distribution of the administered antibody and expressions of VEGF and Flk-1 were examined immunohistochemically. The suppression of endogenous VEGF activity caused swelling and vacuolation of endothelial cells and obstruction of capillaries in the glomerulus. Other tissues were not impaired significantly. The administered antibody was specifically localized to the glomerulus, and was found more predominantly in the juxta-medullary than in the cortical glomerulus. This pattern of antibody deposition was similar to that of Flk-1. VEGF expression in the glomerulus was compensatively elevated by the antibody treatment. These results show that demand for VEGF signaling in the glomerulus is much higher than in other tissues, probably to protect its endothelial cells against high tension for blood filtration. This demand may be fulfilled by enriched signaling through the Flk-1 in the glomerulus.

Correlation of immunohistochemical molecular staging of bladder biopsies and radical cystectomy specimens

PURPOSE

To determine the relationship of p53, retinoblastoma (RB), and p16 expression between precystectomy transurethral resection bladder (TURB) biopsy and matched cystectomy specimens; and to determine the value of p53 immunoreactivity for predicting progression and survival in patients undergoing radical cystectomy.

METHODS AND MATERIALS

We performed p53 immunohistochemical staining on matched archival TURB and cystectomy specimens taken from 40 patients. Twenty-seven and 26 of these patients were also evaluated for RB and p16 expression, respectively.

RESULTS

Twenty-eight (70%) of the TURB and 22 (55%) of the cystectomy specimens stained positive for p53. RB and p16 protein expression were altered in 19 (70%) and 19 (73%) of the TURB specimens, respectively, and 19 (70%) and 19 (73%) of the cystectomy specimens, respectively. There was a strong correlation between p53, RB, and p16 expression and TURB and cystectomy specimens (all p < 0.001). In preoperative and postoperative multivariate analyses, biopsy p53 and cystectomy p53 were independently associated with disease progression (p = 0.049 and p = 0.034, respectively) and bladder cancer-related death (p = 0.044 and p = 0.037, respectively).

CONCLUSION

p53, RB, and p16 expression patterns on TURB specimens correlate with cystectomy specimens. p53 immunoreactivity is an independent predictor of disease progression and bladder cancer survival. These data support the potential of prognostic staging using immunohistochemical analysis on bladder biopsy specimens prior to neoadjuvant or definitive therapy.

Reappraisal of the historic 1959 cat experiment in Minamata by the Chisso Factory

Autopsy specimens from the historic cat experiment were recently discovered in a storage area at the Kumamoto University School of Medicine. The specimens were from an experiment prompted by physicians in the Chisso Minamata Plant following the announcement made by the Study Group for Minamata disease. On July 14, 1959 the Group announced that the disease was most likely caused by a kind of organic mercury. In order to prove or disprove that industrial waste from the Chisso Factory was the culprit in Minamata disease, a total of ten cats were fed food mixed with industrial waste produced in the acetaldehyde-producing plant. One of the ten cats, No. 717, was subsequently autopsied but the autopsy findings have never been published or recorded in the literature despite their historic significance. The rediscovered specimens were studied pathologically and biochemically, and were analyzed chemically with currently available techniques. Characteristic lesions of methylmercury poisoning were observed in the central nervous system, and the mercury levels in the cerebrum, cerebellum, liver and kidney were found to be markedly elevated in this animal.

Toward a tobacco-free society in Japan

Tobacco is one of the major preventable causes of death and disability. This is widely known in both Japan and the USA, and although the smoking rate in the USA is decreasing, that in Japan remains high. The tobacco histories of these two countries, which provide the background to this difference, are herein compared. The antismoking movement is becoming more vociferous in both countries. Publicity regarding of the dangers of smoking, warning signs on tobacco packages, the introduction of antismoking devices, a ban on commercials for tobacco-related products on TV and the radio, no-smoking seats on airplanes, and litigation against the tobacco industry have all been introduced. However, major differences remain between these two countries. The tobacco industry in the USA has been a private company since it was first established. Courts have ordered the tobacco industry to pay compensation for damage to health resulting from tobacco. Smoking is strictly restricted inside buildings. Advertisements for nicotine gum and nicotine patches and reports on the dangers of smoking are regularly broadcast. In the case of Japan, the government at first nationalized the tobacco industry, and then made it a private company, although the government still holds two-thirds of its stock. Moreover, it established the Tobacco Business Law to support the company. The main purpose of antismoking campaigns in Japan is a partial ban on smoking. On the basis of these differences between the two countries regarding the history of tobacco, the antismoking movement in Japan has yet to choose which path to take.

[A case of congenital hydronephrosis suffering from rupture of the renal pelvis due to trauma]

A 19-year-old male patient was admitted with the chief complaint of left abdominal pain. After receiving a mild punch in the abdomen during boxing exercises, he had severe abdominal pain and was brought to an emergency room. Since abdominal CT scanning revealed the retention of massive fluid in the retroperitoneum, hydronephrotic rupture due to the trauma was diagnosed and nephrectomy was performed. The removed kidney was filled as a result of urinary retention, and congenital hydronephrosis accompanied by the ureteropelvic junction obstruction was macroscopically and pathohistologically diagnosed. Postoperative course was favorable and the patient was discharged on the 10th hospital day.

Molecular cloning of groESL locus, and purification and characterization of chaperonins, GroEL and GroES, from Bacillus brevis

The groESL locus of a protein-hypersecreting bacterium, Bacillus brevis, was cloned by PCR using primers designed based on the DNA sequence of a B. subtilis homolog. GroEL protein was purified to apparent homogeneity and its ATPase activity was characterized: it hydrolyzed ATP, CTP, and TTP in this order of reaction rate, and its specific activity for ATP was 0.1 micromole/min/mg protein. Purified GroEL forms a tetradecamer. GroEL was estimated to contain 22% alpha-helix, 24% beta-sheet, and 19% turn structures, by CD measurement. GroES protein was also highly purified to examine its chaperonin activity. GroEL protected from thermal inactivation of and showed refolding-promoting activity for malate dehydrogenase, strictly depending on the presence of ATP and GroES.

In vivo protection of a water-soluble derivative of vitamin E, Trolox, against methylmercury-intoxication in the rat

Methylmercury (MeHg) is a well-known neurotoxicant. MeHg-intoxication causes a disturbance in mitochondrial energy metabolism in skeletal muscle and apoptosis in cerebellum. We report the first in vivo effectiveness of antioxidant Trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carhoxylic acid), a water soluble vitamin E analog, against the MeHg-induced cellular responses. Treatment with Trolox (6-hydroxy-2.5,7,8-tetramethylchroman-2-carboxylic acid) clearly protects MeHg-treated rat skeletal muscle against the decrease in mitochondrial electron transport system enzyme activities despite the retention of MeHg. Tdt-mediated dUTP nick-end-labeling method clarified that Trolox is effective for protecting cerebellum from MeHg-induced apoptosis. These data indicate that MeHg-mediated oxidative stress plays an important role in the in vivo pathological process of MeHg intoxication. Trolox may prevent some of clinical manifestations of MeHg-intoxication in humans.

Efficient expression, purification and characterization of mouse salivary alpha-amylase secreted from methylotrophic yeast, Pichia pastoris

We constructed a secretion vector of mouse salivary alpha-amylase, pPAM, using the AOX1 promoter-terminator and the secretion signal of 128 kDa pGKL killer protein, for an alternative yeast, Pichia pastoris. Taking advantage of multicopy insertion of the expression cassette and optimized growth conditions, we succeeded in highly efficient extracellular production (approximately 240 microg/ml) of mouse alpha-amylase in the 10 ml scale by conventional flask culture: this efficiency was about 90-fold higher than that of Saccharomyces cerevisiae. Growth temperature of cells was critical for efficient production of alpha-amylase. P. pastoris transformants secreted both core-glycosylated and non-glycosylated alpha-amylase molecules with a glycosylated:non-glycosylated ratio of about 20:80. Both glycosylated and non-glycosylated alpha-amylases were purified separately to apparent homogeneity. The signal sequence was correctly processed in both species, and the molecular masses of glycosylated and non-glycosylated alpha-amylase were determined to be 58 600 and 56 300, respectively, by mass spectrometry. We further studied the outer chain glycosylation of engineered mouse alpha-amylase secreted by P. pastoris.

NaCl-activated nucleoside diphosphate kinase from extremely halophilic archaeon, Halobacterium salinarum, maintains native conformation without salt

Enzymes from extremely halophilic archaea are readily denatured in the absence of a high salt concentration. However, we have observed here that a nucleoside diphosphate kinase prepared from Halobacterium salinarum was active and stable in the absence of salt, though it has the amino acid composition characteristic of halophilic enzymes. Recombinant nucleoside diphosphate kinase expressed in Escherichia coli requires salt for activation in vitro, but once it acquires the proper folding, it no longer requires the presence of salts for its activity and stability.

An association between an antibody against Chlamydia pneumoniae and common carotid atherosclerosis

OBJECTIVE

Chlamydia pneumoniae (C. pneumoniae) is an important pathogen for infections of the respiratory tract, and there are recently also a number of reports suggesting its relation with atherosclerosis. This study was performed to clarify the relation between C. pneumoniae infection and sclerotic lesions of the common carotid arteries.

METHODS AND PATIENTS

We evaluated sclerotic lesions of common carotid arteries by ultrasonography in 147 in-patients (mean age, 70 years; 95% confidence interval, 68-72) in the internal medicine ward, and studied the relation of the known risk factors for atherosclerosis including C. pneumoniae infection. An ultrasonograph and 7.5 MHz linear type B-mode probe were used by a specialist to evaluate sclerotic lesions of common carotid arteries. C. pneumoniae infection was determined by measuring anti-C. pneumoniae IgG specific antibody level (IgG index) using enzyme-linked immunosorbent assay (ELISA) method with serum of fasting blood, which had been preserved at -70 degrees C.

RESULTS

IgG index (p=0.0263), from multiple regression analysis using various risk factors as explanatory variables, was a significant independent contributing factor (R2=0.3465, p<0.0001) along with known risk factors such as male (p=0.0289), age (p=0.0007), Brinkman index (p=0.0067), hypertension (p=0.0443) and T-Chol (p=0.0220).

CONCLUSION

This study confirmed that the observations of an association between antibody against C. pneumoniae and common carotid atherosclerosis in Western nations is also present in Japan. Our results suggests that C. pneumoniae infection is also an important risk factor for common carotid atherosclerosis.

Expression, purification, and characterization of the active immunoglobulin-like domain of human granulocyte-colony-stimulating factor receptor in Escherichia coli

We succeeded in the expression, purification, and refolding of the immunoglobulin-like (Ig) domain of human granulocyte-colony-stimulating factor (G-CSF) receptor with amino-terminal His-tag in Escherichia coli. The refolded Ig domain bound to a G-CSF affinity column and could be eluted with free G-CSF as a receptor-ligand complex, demonstrating that the Ig domain has the information necessary for binding its ligand, G-CSF. The eluted His-Ig/G-CSF complex could be separated from excess G-CSF by Ni-NTA column chromatography. The yield of this active recombinant His-Ig protein is about 0.72 mg per liter of culture. Its small size and the ease of production make this receptor fragment a useful reagent for the structural analysis of its complex with G-CSF.

Expression and purification of cytokine receptor homology domain of human granulocyte-colony-stimulating factor receptor fusion protein in Escherichia coli

Direct expression of the cytokine receptor homology (CRH) domain of granulocyte-colony-stimulating factor (G-CSF) receptor is lethal to Escherichia coli. For the efficient and stable production of an active CRH domain in E. coli, we fused the CRH domain with different proteins, such as maltose-binding protein (MalE), glutathione S-transferase, and thioredoxin (Trx). Among these, Trx appeared to be the best in terms of the protein expression level, purification efficiency by affinity chromatography, and binding activity to its ligand, G-CSF. The yield of active Trx-CRH fusion protein increased about 200-fold compared to that of previously reported MalE-CRH fusion.

Endothelin receptor antagonist prevents parathyroid cell proliferation of low calcium diet-induced hyperparathyroidism in rats

Secondary hyperparathyroidism, one of the most frequently encountered disorders of the calcium homeostasis, is characterized by an increase in parathyroid epithelial (PT) cell number, which is crucial from a functional viewpoint. However, it is still unknown what factors are involved in PT cell proliferation. Endothelin-1 (ET-1), a vasoconstrictive peptide, has been shown to act as a mitogen in a variety of cell types. Rat PT cells are reported to synthesize ET-1 and possess its receptors. To test the hypothesis that ET-1 plays a role in PT cell proliferation, we used rat test subjects fed a low calcium diet for 8 weeks (low Ca rats). The number of the proliferating PT cells, measured by proliferating cell nuclear antigen immunostaining, was significantly increased, with striking immunoreactivity of ET-1 in the low Ca rats. An endothelin receptor antagonist, bosentan (100 mg/kg.day), prevented any increase in the proliferation of PT cells in the low Ca rats (14.3 +/- 2.7/1000 PT cells with no bosentan; 2.1 +/- 1.3 with bosentan; P < 0.01). These results indicate that ET-1 is involved in PT cell proliferation in vivo and suggest that blocking of ET receptors may become one of the important therapeutic strategies for preventing secondary hyperparathyroidism.

Secretion of hen egg white lysozyme from Kluyveromyces lactis

Hen egg white (HEW) lysozyme was correctly processed and efficiently secreted from an alternative yeast, Kluyveromyces lactis. We constructed secretion vectors using PHO5, PGK, and LAC4 promoters, and found that the highest secretion was obtained under the direction of the PGK promoter in non-selective rich medium. K. lactis secreted HEW lysozyme with two-fold higher efficiency than S. cerevisiae, estimated by using a K. lactis-S. cerevisiae shuttle vector.

Functional anatomical study of psychogenic amnesia

Psychogenic amnesia is characterized by an inability to recall information already stored in the patient's memory. It is usually related to a stressful or traumatic event that cannot be explained by manifest brain damage. To examine the underlying functional disturbance of brain areas in this condition, we performed a positron emission tomography (PET) activation study on a psychogenic amnesic patient and on 12 normal control subjects. A task requiring explicit retrograde memory of faces was compared with a control task. To assess functional modifications associated with the processes of recovery, a second PET study was performed on the patient 12 months after onset. During the task, activation of the right anterior medial temporal region including the amygdala was increased in the psychogenic amnesic patient. Activation of the bilateral hippocampal regions increased only in the control subjects. During recovery, the right anterior medial temporal region became less active while the right hippocampal region became more active. Activation levels also differed in the anterior cingulate cortex, prefrontal cortex and some other cortical regions between control subjects and the patient. These findings suggest that the changes in these limbic and limbic-cortical functions are related to symptoms of the psychogenic amnesia.

Expression of bone morphogenetic protein receptors type-IA, -IB and -II correlates with tumor grade in human prostate cancer tissues

Bone morphogenetic proteins (BMPs) are potential regulators of prostate cancer cell growth and metastasis that signal through an interaction with BMP membrane receptors (BMPRs) type I and type II. In the present study, Western blot and immunohistochemical analysis of BMPRs were carried out in benign and malignant human prostate tissues to explain the loss of BMP response in human prostate cancer cells. The results demonstrated that the benign prostate specimens expressed high levels of all three BMPRs. In normal prostate, BMPRs were localized predominantly to epithelial cells. Among prostate cancer specimens, well-differentiated cancers were positive for the expression of BMPR-II, BMPR-IA, and BMPR-IB, for the most part. In contrast, only 1 of 10 poorly differentiated prostate cancer cases was positive for each of the three BMPRs (P < 0.005 for all three receptors). Taken together, these results indicate that human prostate cancer cells frequently exhibit loss of expression of BMPRs and suggest that loss of BMPRs may play an important role during the progression of prostate cancer.

[VEGF is an essential molecule for glomerular endothelial cells and its excretion in urine might be a unique marker of glomerular injury]

A glomerulus is a functional unit of the kidney, and endothelial cells in the glomerulus are often exposed to more than 5 times higher pressure than peripheral capillaries. Glomerular development proceeds through angiogenesis and VEGF was shown to mediate the angiogenesis. VEGF is constitutively expressed in the glomerulus from the embryo to adults. When VEGF signal was blocked by the antibody, glomerular endothelial cells were swollen and capillary lumen was interrupted. Changes were more prominent in the juxta-medullary than in the cortical glomerulus. A major VEGF receptor, Flk-1/KDR, is specifically localized to the glomerular endothelial cell among tissues and more predominantly in the juxta-medullary than in the cortical glomerulus. As capillary pressure is higher in the juxta-medullary than in the cortical glomeruli, endothelial cells in the former are exposed to more tension than those in the latter. VEGF might be a protective molecule for endothelial cells against tension. The effect of VEGF on the repair of an impaired glomerulus was evaluated in the rat Thy-1 glomerulonephritis. VEGF inhibited early endothelial injury and accelerated consequent remodeling of the glomerulus. In the patient study, VEGF excretion in the urine was independent from its serum or plasma level, but increased as renal function decreased. VEGF signaling is essential in glomerular development, maintenance and repair. VEGF excreted in the urine might reflect its generation in the kidney and be a unique marker of renal function.

[The correlation between the exacerbation of bronchial asthma and picornavirus (human rhino virus) infection in throat gargles by RT-PCR]

Viral infection is one of important factors to cause the exacerbation of bronchial asthma. We have investigated 167 adults of asthmatics to clarify the correlation between viral infection and exacerbation of asthma. Patients were classified to four group by the symptoms of common cold and asthma attack. Furthermore, we have examined Picornavirus and Human rhino virus RNA from throat gargles of patients using RT-PCR (reverse transcription--polymerase chain reaction) method. Forty of 65 (61.5%) asthmatics with common cold revealed asthma attack and common cold was significantly associated with acute exacerbation of asthma (p < 0.01). We identified Picornavirus RNA, which include 113 of Human rhino virus serotypes and enterovirus, from the samples of 16 of 52 (30.8%) patients who had acute exacerbation. It was significantly higher than the detection rate of viral RNA from patient without asthma attack. Furthermore, we analyzed Human rhino virus RNA from the same samples by RT-PCR and 93.7% of Picornavirus were identified as Human rhino virus. Taken together, these findings suggest that common cold is significantly associated with the exacerbation of bronchial asthma. Human rhino virus infection might be one of important virus in this procedure.

Growth hormone secreting adenoma with unusual extension: coexisting pituitary cyst and its clinical significance

A 58 year old man showed acromegalic features. The serum growth hormone (GH) level was 7.3 ng/ml and SMC (somatomedin-C) 637 U/ml. Triple stimulation test showed abnormal response compatible with a GH secreting tumour. The conventional enhanced MRI revealed a less enhanced hemisphere-shaped lesion at the right corner of the sella turcica. In addition, dynamic MRI demonstrated an elongated lesion extending to the left beyond the midline. The patient underwent transsphenoidal surgery. Besides the soft and suckable tumour at the right corner, we entered into a small cavity loosely filled with the tumour, which was subsequently also removed. The operative finding corresponded to the lesion shown in dynamic MRI. Postoperative GH and SMC levels became 2.3 ng/ml and 326 U/ml respectively. Incidental pituitary cystic lesions in autopsied cases have been reported to be 6-33%. This case had a GH secreting adenoma with coexisting pituitary cyst. The coexisting pituitary cyst supposedly influenced the unusual shape and extension of the pituitary adenoma. Coexistence of such lesion should be kept in mind for microadenoma on neuroradiological evaluation and on intraoperative inspection surrounding the tumour.

The neural basis of perceptual and conceptual word priming--a PET study

Positron emission tomography scans were obtained in 13 normal subjects during perceptual and conceptual word priming tasks with the aim to investigate the neural system specific to the two priming conditions. In the prescan phase, subjects were primed perceptually or conceptually with two separate procedures, while in the scan phase, they performed the same stem completion task. Therefore we could compare the results of the two priming tasks in a direct manner. A fixation control task and a baseline task (completion of stems that did not correspond to previously seen words) were also given. A specific blood flow decrease was found in the left inferior temporal cortex in the perceptual word priming condition and in the left superior temporal / inferior parietal cortex in the conceptual word priming condition. Each blood flow change may reflect transient changes in the cortical areas subserving the processing of the perceptual and conceptual components of word priming.

Sodium-dependent calcium release from vascular smooth muscle mitochondria

Interest in mitochondrial calcium (Ca2+) uptake and release waned as it became apparent that sarcoplasmic reticulum calcium stores dominate the control of cytoplasmic calcium concentration. Our recent demonstration of a very large rise in vascular smooth muscle (VSM) cytoplasmic sodium (Na+) concentration after inhibition of the sodium, potassium-ATPase (sodium pump) led us to several questions. Do VSM mitochondria show Na(+)-dependent Ca2+ release? Are the documented changes in cytoplasmic Na+ concentration sufficient to cause Ca2+ release? Do features of the cardiac mitochondrial exchange system, including differential sensitivity to a number of calcium antagonists and cation specificity, apply to VSM? We isolated mitochondria from bovine aorta and mesenteric arteries and employed arsenazo III as the Ca2+ indicator. Mitochondria from arterial vessels accumulated added calcium (up to 50 nmol Ca2+/mg protein) and released Ca2+ on exposure to Na+. This concentration-dependent relationship was linear from 0 to 10 mM of Na+, and it plateaued between 20 mM and 40 mM of Na+. VSM mitochondria exposed to 20 mM Na+ released 118 +/- 25 nmol Ca2+ per mg mitochondrial protein in 20 min, when a new equilibrium was reached. Lithium (Li+), in contrast to Na+, produced much smaller amounts of Ca2+ release from the VSM mitochondria. Na+-dependent Ca2+ release was antagonized in a concentration-dependent manner by diltiazem (0-320 microM) with a Ki of 10.2 microM. Nifedipine had a lesser effect, and verapamil produced almost no inhibition. VSM mitochondria responses resemble those from heart mitochondria in that Na+-dependent Ca2+ release is present with a similar range of sensitivity to Na+ and a similar pattern of influence of diltiazem, nifedipine and verapamil. However, the influence of Li+ on Ca2+ release was much smaller and the amount of the Ca2+ released was much greater for VSM mitochondria compared with that reported for heart mitochondria. The large amount of Ca2+ released and the range of Na+ concentration that provoked Ca2+ release being within the physiologically achievable range raise the interesting possibility that these mechanisms may modify intramitochondrial cytosolic Ca2+ concentration, and hence could potentially contribute to the contractile response that follows inhibition of the sodium pump.