Lymph flow and lymph node metastasis in esophageal cancer

This paper delineates which lymph nodes should be dissected due to the high frequency of metastasis associated with different types of primarily lesions of the thoracic esophagus. In cancer involving the upper third of the esophagus (Iu), lymph flow was found to be primary from the superior mediastinal area to the cervical area; in that involving the middle third (Im), it was broadly distributed from the superior, middle, and inferior mediastinal region to the cervical and abdominal regions; and in that involving the lower third (Ei), it tended to extend from the inferior mediastinal region to the abdominal region, with single primary metastatic nodes also being noted in this area. The significance of the "top" nodes, namely, the nodes located along the right recurrent laryngeal nerve in the upper portion of the thorax, was also investigated, and it was confirmed that the prognosis for patients with metastases to both the top nodes and other nodes was unfavorable. An immunohistochemical study on mediastinal lymph flow using the anti-Su-Ps antibody demonstrated interactions between top nodes and cervical and/or thoracic nodes.

Impaired high-shear-stress-induced platelet aggregation in patients with chronic renal failure undergoing haemodialysis

We investigated shear-induced platelet aggregation (SIPA) in 30 patients with chronic renal failure (CRF) undergoing haemodialysis. 26 patients showed a significant decrease in SIPA at high shear stress but no change in SIPA at low shear stress. The former reaction reflects the interaction between plasma von Willebrand factor (vWF) and its platelet receptors, glycoprotein (GP) Ib-IX and IIb/IIIa complex, whereas the latter is assumed to involve the binding of plasma fibrinogen to GP IIb/IIIa complex. These SIPA profiles in CRF patients after haemodialysis showed almost no change compared to those before haemodialysis. The ratio of ristocetin cofactor/vWF antigen in plasma was slightly lower in CRF patients than in controls (P < 0.01). However, the level of GPIb antigen in the platelets of these patients was significantly reduced (42.1 +/- 20.3% of normal platelets), with partial destruction of GPIb antigen. The number of vWF receptors on the GPIb molecule was quantitated using the GPIb-binding protein alboaggregin-B (AL-B), purified from the snake venom of Trimeresurus albolabris. AL-B bound to GPIb at a total of 48,760 +/- 9944 molecules per normal platelet and a Kd of 85.44 +/- 15.70 nM at saturation. In contrast, binding in CRF platelets was 22,980 +/- 6395 molecules per platelet and Kd was 50.08 +/- 13.83 nM. Taking these results together, we conclude that the impaired SIPA found in CRF patients is due to both abnormalities in plasma vWF and in its platelet GPIb receptor.

Intraarterial infusion of dibutyryl cyclic adenosine monophosphate plus mitomycin C for unresectable hepatocellular carcinoma: long-term survival and response to tumor growth inhibition

RATIONALE AND OBJECTIVES

Dibutyryl cyclic adenosine 3',5'-monophosphate (dBcAMP) has the capacity to promote morphologic differentiation and to inhibit tumor growth in vitro, but it has not been well researched in the clinical setting. In this study we examined the effects of intraarterial infusion of dBcAMP plus mitomycin C (MMC) on long-term survival and growth inhibition of tumors.

METHODS

Thirty-one previously untreated patients with unresectable hepatocellular carcinoma (HCC) received intraarterial infusion of dBcAMP plus MMC. According to the International Union Against Cancer staging system, three patients had stage T3, eight had stage T4a, and 20 had stage T4b cancer. Growth inhibition was defined as no computed tomography (CT) scan evidence of increase in tumor diameter for at least 6 months after treatment.

RESULTS

In all 31 patients with HCC, the cumulative survival rate was 34% at 1 year, 14% at 3 years, and 9% at 5 years. The median survival was 5.0 months, with the longest survival period being 92 months. Among 21 patients in whom a tumor response could be evaluated on the basis of follow-up CT studies, two had complete regression of their primary tumors. Overall, the response rate was 43% (9 of 21). Among the 12 stage T4b patients who had HCC that included the main trunk and its major branches of the portal vein, portal thrombi had disappeared in four (33%). Among eight patients who survived more than 1 year and were evaluated for tumor response using follow-up CT scan studies, six (75%) had growth inhibition of tumor.

CONCLUSION

Chemotherapy combined with dBcAMP and MMC showed a favorable response in approximately one third of 31 patients who had unresectable HCC. Because of our results, combined therapy should be strongly considered in the treatment of patients with HCC including occlusion of the main portal vein.

Metabolic profile of opioid peptides differs in the hippocampus and striatum of seizure-susceptible E1 mice

We previously suggested that a deficit of anticonvulsant endogenous methionine enkephalin, in the cerebral cortex, septal area, hippocampus, and striatum of seizure-susceptible El mice plays a role in the pathogenesis of seizures. To determine whether a hypofunction of enkephalinergic neuron may be due to metabolic abnormalities of opioid peptides in the El mouse brain, we measured methionine enkephalin-like immunoreactivity (ME-LI) of 50 fractions eluted by high performance liquid chromatography obtained from those four regions of the brain of El and seizure-nonsusceptible ddY mice (the mother strain of El mice). We observed the same ME-LI patterns of 50 fractions in the cerebral cortex and septal area in El and ddY mice, whereas exhibited differing ME-LI patterns in the hippocampus and striatum in the two stains. Different ME-LI patterns may imply the difference in the metabolic profile of opioid peptides. Thus, an abnormal metabolism of opioid peptides in the hippocampus and striatum of the El mouse may be involved in the pathogenesis of seizures.

Comparison of therapeutic efficacies of type A and F botulinum toxins for blepharospasm: a double-blind, controlled study

Type F botulinum toxin can be used for treating patients with dystonia who become refractory to type A toxin injection due to antibody development. We compared the therapeutic efficacy of type F botulinum toxin to that of type A toxin in a self-controlled, double-blind clinical trial. In nine patients with blepharospasm, we injected type A toxin on one side and the same units of type F toxin on the other side. Although the onset of clinical effect, maximal benefit, and adverse reactions were similar between type A and F toxins, the duration of the clinical effect was significantly shorter on the side injected with type F toxin. Although type F toxin proved its promise as an alternative to type A toxin, its usefulness is limited by the shorter duration of action.

Inhibition of endothelial nitric oxide synthase activity by protein kinase C

Nitric oxide (NO) is an important molecular messenger accounting for endothelium-derived relaxing factor. Recently, NO synthase (NOS) from cultured endothelial cells has been purified and molecularly cloned. To evaluate the effect of phosphorylation by protein kinase C (PKC) and cyclic AMP-dependent protein kinase (PKA) on endothelial constitutive NOS catalytic activity, we incubated purified endothelial NOS with PKC or PKA. Endothelial NOS was stoichiometrically phosphorylated by PKC and PKA. In intact bovine aortic endothelial cells (BAECs), NOS was phosphorylated by stimulation with 12-O-tetradecanoylphorbol-13-acetate (TPA). NOS activity measured by the conversion of [3H]arginine to [3H]citrulline in homogenates of BAECs treated with TPA or phorbol 12,13-dibutyrate was reduced by 30%, whereas dibutylyl cyclic AMP did not affect NOS activity. Moreover, we measured NO release from cultured BAECs by a chemiluminescence method to examine the effect of PKC and PKA on endothelial NOS activity. In cultured BAECs, ATP gamma S and A23187 induced NO release in time- and dose-dependent manners. Phorbol esters such as TPA and phorbol 12,13-dibutyrate dose dependently inhibited NO release stimulated by A23187 as well as ATP gamma S. Reduction of NO release by TPA was almost completely prevented by pretreatment with staurosporine, an inhibitor of PKC. NO release by A23187 was increased in PKC-downregulated BAECs. In contrast, dibutylyl cyclic AMP or 8-bromo cyclic GMP had no effect on NO release from BAECs induced by A23187 or ATP gamma S. These results indicate that phosphorylation of NOS by PKC is associated with a reduction of its catalytic activity in vascular endothelial cells.

Fibronectin and 130-kDa molecule complex mimics snake venom botrocetin-like structure potentially modulating association between von Willebrand factor and vascular vessel wall

We established seven hybridomas secreting monoclonal antibodies (MoAbs) against the venom from Bothrops jararaca. Six of them were demonstrated to specifically recognize botrocetin, a venom protein which binds with von Willebrand factor (vWf) and induces platelet agglutination. Two of them, BCT4-3 and BCT115-2 MoAbs, could significantly inhibit botrocetin binding with plasma vWf. BCT4-3 could react slightly with a monolayer of human endothelial cells (ECs), and BCT4-3 binding to ECs was drastically enhanced by the coexistence of human plasma in a dose-dependent manner, indicating that a biological modulator structurally resembling botrocetin is created initially on the EC surface complexed with some plasma proteins. Botrocetin-like components could be immuno-purified only by immobilized BCT4-3, but not by the other immobilized MoAbs, from umbilical vein extracts. Interestingly, the immunoisolated materials were identified to consist essentially of fibronectin (Fn) and a 130 kDa molecule, and this complex bound to vWf in the extracts. Depletion of Fn from plasma decreased BCT4-3 binding to ECs. The epitope of BCT4-3 expressed on the endothelial surface, comprising plasma Fn and the coisolated 130 kDa molecule, is proposed to be a physiological modulator structurally mimicking botrocetin, and essentially supporting vWf-binding to injured endothelium and subsequently to circulating platelets.

A comparison of hard and soft copies processed with linear conversion and nonlinear conversion of skeletal fractures--a preliminary study

To compare hard copies and soft copies processed with linear and nonlinear conversion of skeletal fractures, we performed a receiver-operating characteristics study of 25 digital radiographs. There was no statistical difference between hard copies with linear and nonlinear conversion. However, it may be difficult to detect small fractures on images processed by nonlinear conversion. No significant difference was seen between CRT diagnosis and that on a hard copy processed with linear conversion and frequency enhancement.

A case of an intra-atrial tumor thrombus from hepatocellular carcinoma (HCC), first indicated by 67Ga-citrate scintigraphy

We encountered a very rare case of an intra-atrial tumor thrombus from hepatocellular carcinoma (HCC). Conventional XCT and US gave evidence of HCC. In nuclear medicine studies performed incidentally, the first study with 99mTc-phytate liver scintigraphy showed 2 SOLs and evidence of chronic liver disease, and the second study with 67Ga-citrate scintigraphy demonstrated 2 hot lesions within the liver parenchyma, and also another unexpected hot area just above the left lobe of the liver, seemingly beyond the diaphragm. When echocardiography was performed, in addition to ECG, because the patient began to complain of dyspnea, an oblong mass lesion was detected within the right atrium. Reexamination with XCT and angiography clearly proved the existence of an intraatrial tumor thrombus. These results indicate the need for routine examination by echocardiography for HCC patients complaining of dyspnea.

[A case of mixed connective tissue disease associated with gastric cancer and cancer of the uterine cervix]

We report here a very rare case of MCTD complicating double cancer. A 43-year-old woman with suspected MCTD was admitted because of high fever and lymphadenopathy. The laboratory findings indicated high titers of speckled ANA, anti-RNP, DNA and Scl-70, but anti-Sm. SS-A and SS-B was not detected. Chest CT and Spirogram revealed lung fibrosis, restrictive ventilatory impairment, and decreased diffusion capacity. Biopsy specimen by gastric fiberscope s screening indicated II c advanced type of poorly differentiated adenocarcinoma. After subtotal gastrectomy, she had high fever, pleuritis, leukopenia, butterfly erythema and hypoxemia, which were improved by 30 mg/day of oral prednisolone. One year after from the last operation, she had contact bleeding, and squamous cell carcinoma of the uterine cervix was diagnosed. She had Raynaud's phenomenon 6 months after from hysterectomy.

Effect of indomethacin on lung development in postnatal rats: possible role of prostaglandin in alveolar formation

We administered 1.3 mg ip of indomethacin, a prostaglandin synthetase inhibitor, per 100 g body wt to male rat pups daily on postnatal days 4-13 and examined their lungs on day 14. Indomethacin administration produced abnormal lung structure with diminished alveolar air, increased alveolar duct air, increased mean linear intercept (gas-exchanging wall distance), diminished gas-exchanging surface area and surface-to-volume ratio, increased septal wall thickness, diminished the number of alveolar crests, and increased the number of lamellar bodies in alveolar type II cells. However, this procedure did not alter quantitative lung growth (normal lung weights, volumes, and DNA and protein contents). Tissue prostaglandin content was decreased. The total amount of lung collagen or elastin was unchanged, but when collagen was analyzed into soluble and insoluble components, soluble collagen was increased. Supplementation with 1.0 g of prostaglandin E2 per 100 g body wt to animals treated with indomethacin reduced the abnormalities in pulmonary architecture. We conclude that indomethacin affects lung structure in growing rats and that it is an unusual model in that lung growth is normal, but lung development is abnormal. We also suggest that prostaglandins may play a significant role in alveolar formation in postnatal lung development in rats.

Effects of bifemelane hydrochloride on plasma neuropeptide Y, 3-methoxy-4-hydroxyphenylethylene glycol and 5-hydroxy-indole acetic acid concentrations in patients with cerebral infarction

Bifemelane hydrochloride (BH) is widely employed in Japan in the treatment of cerebral infarction patients with depressive symptoms and its antidepressant action is considered to be caused by the normalizing effects of neurotransmitters. The relationship between the normalizing effects of neurotransmitters of BH and the depressive state of patients with cerebral infarction was examined. BH 150 mg/day was administered for three months to 13 cerebral infarction patients with depressive state. We measured the plasma neuropeptide Y (NPY), 3-methoxy-4-hydroxyphenylethylene glycol (MHPG) and 5-hydroxy-indole acetic acid (5-HIAA), and assessed the depressive symptoms using the 21-item Hamilton's Rating Scale for Depression (HRSD) before and after administration of BH. After treatment, the plasma NPY concentration was significantly increased, the plasma MHPG concentration and total score of HRSD were significantly decreased, and the plasma 5-HIAA concentration showed no changes. These findings suggest that the antidepressant effect of BH is caused by the normalizing effects of NPY and noradrenalinergic neurons.

Inositol 1,4,5-trisphosphate formation and ryanodine-sensitive oscillations of cytosolic free Ca2+ concentrations in neuroblastoma x fibroblast hybrid NL308 cells expressing m2 and m4 muscarinic acetylcholine receptor subtypes

Intracellular free Ca2+ concentrations ([Ca2+]i) were measured in subclones of NL308 neuroblastoma x fibroblast hybrid cells expressing each of the individual muscarinic acetylcholine receptor (mAChR) subtypes m1, m2, m3 and m4. Application of 100 microM acetylcholine (ACh) increased [Ca2+]i in all four subclones. The increased [Ca2+]i levels were significantly higher in m1- and m3-transformed cells than those in m2- and m4-transformed cells. In more than 95% of m2- and m4-transformed cells, [Ca2+]i showed sinusoidal oscillations. ACh-induced increases in [Ca2+]i were not observed in cells treated with an intracellular Ca2+ chelator, 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA). Removal of extracellular Ca2+ with ethylene-glycol-bis-(beta- aminoethyl)-N,N,N',N'-tetraacetate (EGTA) did not affect the initial [Ca2+]i increases, but reduced the late phases of delta [Ca2+]i in ml- and m3-transformed cells by 20-30%. Oscillations in m2- and m4-transformed cells persisted in EGTA solution (though sometimes slowed in frequency), suggesting that they were of intracellular origin. ACh-induced delta [Ca2+]i and inositol 1,4,5-trisphosphate formation was completely suppressed by pre-treatment with 50-100 ng ml-1 Pertussis toxin (PTX) for 12 h in m2- and m4-transformed cells, but not in m1- and m3-transformed cells. In all cells, extracellular application of caffeine and ryanodine, or intracellular application of cyclic adenosine diphosphate ribose (cAD-PR) produced a rise in [Ca2+]i. ACh-induced [Ca2+]i oscillations were not observed in ryanodine-treated m2-transformed cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Alternative treatment may lower the need for use of extracorporeal membrane oxygenation

Access to artificial surfactant and high frequency oscillatory ventilation (HFO) in Japan seems to affect the actual indications for extracorporeal membrane oxygenation (ECMO). The relation between the methods of treatment and survival and/or neurological sequelae of 27 neonates with severe respiratory failure who would have met the US ECMO entry criteria in the Neonatal Intensive Care Unit of National Children's Hospital, Tokyo between January 1988 and May 1992 were retrospectively analyzed. Out of 27 neonates, conventional treatment including artificial surfactant was successful in 6 cases (22%). High frequency oscillatory ventilation was used for the 21 cases who did not respond to conventional treatment and it was effective in 5 cases (19% of total). Extracorporeal membrane oxygenation was used on 11 (40% of total) of 16 cases who did not respond to HFO. Eight (29% of total or 73% of ECMO cases) of these cases survived and 3 cases (11% of total) died. The remaining 5 cases (19% of total) who met the exclusion criteria of ECMO died. No patient with respiratory distress syndrome (RDS) became ill enough to meet the US ECMO entry criteria. Six out of 8 congenital diaphragmatic hernia cases were saved on a delayed surgery protocol with HFO. Only about 1% of the neonates who were admitted to our NICU during the last 4 years needed ECMO treatment. Forty-one per cent of the patients who would have met the US ECMO entry criteria were treated successfully without ECMO. The necessity for ECMO is less in Japan than in the US because other methods can often be used successfully to treat severe respiratory disorders.

[Thyroid scintigraphy in patients with thyroid tumors using 99mTc-hexakis 2-methoxy isobutyl isonitrile]

Early and delayed thyroid scintigraphy with 99mTc-hexakis 2-methoxy isobutyl isonitrile (99mTc-MIBI) was performed in 18 patients with thyroid tumor, including 8 with papillary carcinoma, 1 each with follicular carcinoma, anaplastic carcinoma, and malignant lymphoma, and 7 with thyroid adenoma. Scintigrams obtained were compared with those taken with other radionuclides. In all 11 patients with malignant tumors, increased 99mTc-MIBI uptake was noted in the tumors on early images, although anaplastic carcinoma and malignant lymphoma had mild uptake. On delayed images, 99mTc-MIBI washout was noted in 45.4% (5/11). In one patient with extensive cervical lymph node metastasis, 99mTc-MIBI concentration was evident in the metastatic foci. In the 4 where, the thyroid adenoma consisted mainly of cystic degeneration, a focal defect was noted, but two of the three patients whose thyroid adenoma consisted mainly of a solid component had an intense tracer uptake in the tumors on early and delayed images. In conclusion, there were increased 99mTc-MIBI accumulations in all of the 14 solid thyroid tumors. The quality of 99mTc-MIBI scintigraphic images of thyroid tumors was equal or slightly superior to that taken with 201Tl scintigraphy. 99mTc-MIBI thyroid scintigraphy may be useful in detecting a solid thyroid tumor and its metastasis, although it cannot be used to differentiate between benign and malignant tumors.

Immunoenzymometric analysis for expression and shedding of intercellular adhesion molecule-1 on human endothelial cells stimulated with cytokines or lipopolysaccharide

Unstimulated endothelial cell (EC) cultures express low levels of intercellular adhesion molecule-1 (ICAM-1) and their expression can be enhanced by inflammatory cytokines such as tumor necrosis factor alpha (TNF). Three monoclonal antibodies (MoAbs) highly reactive with TNF-stimulated human ECs were established and defined to recognize a 95 kDa cell surface protein specifically expressed on cytokine-activated ECs, which was immunochemically identified as ICAM-1. The quantitative immunoassay of soluble and insoluble ICAM-1 could be performed with two different MoAbs. Secretion of fibronectin or the von Willebrand factor, was not significantly enhanced with TNF stimulation. Cellular expression of ICAM-1 was drastically induced by TNF or interleukin-1 stimulation, and the moderate expression with delayed-action was observed only by lipopolysaccharide stimulation. A maximal amount of soluble ICAM-1 was released from ECs stimulated only by TNF, apparently in a dose dependent manner, but no significant release of ICAM-1 was induced by thrombin interleukin-2, or lipopolysaccharides. Released levels of soluble ICAM-1 from interleukin-1-stimulated ECs were apparently diminished as compared with those from TNF-stimulated cells. These results suggest that release of soluble ICAM-1 from EC surfaces can be most significantly enhanced by TNF-specific signaling, and prospectively, should be a sensitive indicator of intravascular inflammation in acute endothelium injury.

Alternatively spliced isoform of P-selectin is present in vivo as a soluble molecule

To demonstrate the presence of a soluble isoform of P-selectin predicted from cDNA sequencing (Johnston, G.I., Bliss, G.A., Newman, P.J., and McEver, R.P. (1990) J. Biol. Chem. 265, 21381-21385), we immunoisolated and compared structurally P-selectin from fresh frozen human plasma with that from washed intact platelets. Plasma P-selectin was reactive with rabbit antiserum to a synthesized peptide (residues 762-774 of mature P-selectin) but was significantly less reactive with antibody to a peptide (residues 747-760). In contrast, platelet P-selectin reacted with both antibodies. S-Pyridylethylated plasma P-selectin was fractionated by reversed phase-high performance liquid chromatography into two major species. From platelets, two virtually identical species were separated. Sequential digestion with Achromobacter protease I and then Staphylococcus V8 protease produced peptides assigned to the tail region of the protein including the putative spliced site. From the more hydrophilic species in both plasma and platelets, a peptide completely lacking the sequence of the putative spliced site was identified. In contrast, the more hydrophobic species yielded a peptide with an intact transmembrane sequence. Hence, these results provide direct evidence that the previously predicted soluble isoform of P-selectin is actually synthesized in vivo and is present as a circulating molecule.

2-Mercaptoethanol-independent survival of fetal mouse brain neurons cultured in a medium of human serum

In primary cultures of fetal mouse brain neurons, medium supplemented with fetal calf serum required 2-mercaptoethanol to support the survival and maturation of neurons, while medium containing human serum did not require the drug. These findings suggest that human serum is more active than fetal calf serum in reducing oxidative stress of neurons.

Effect of ketone bodies on hyperglycemia and lactic acidemia in hemorrhagic stress

BACKGROUND

To investigate the effect of hyperketonemia on altered glucose metabolism under stress conditions, we infused sodium D-3-hydroxybutyrate (3-OHB) into rats in hemorrhagic hypotension and evaluated the plasma concentration of substrates related to glucose metabolism.

METHODS

Three groups of anesthetized rats (weight, 280 g to 320 g) were bled acutely, and their mean arterial pressures were maintained at 40 mm Hg. From 1 hour before hemorrhage to the end of the experiment, rats in the first group (n = 10) were infused with 3-OHB at a rate of 30 mumol/kg.min (3-OHB group), those in the second group (n = 10) received glucose and sodium bicarbonate (glucose group), and the remaining 10 rats received only sodium bicarbonate and no energy substrates (control group). Sodium bicarbonate was used to control the alkalizing effect of 3-OHB.

RESULTS

Hyperketonemia (1158 +/- 30 mumol/L - 1618 +/- 154 mumol/L) occurred only in the 3-OHB group. Hyperglycemia and lactic acidemia during hemorrhagic shock were suppressed significantly compared with the control group. Plasma concentration of alanine was also lower compared with the control group. In the glucose group, although plasma lactate concentration was lower, plasma glucose concentration was not suppressed, and plasma alanine concentration was higher in comparison with the control group during hemorrhagic shock. There was no significant difference in plasma insulin concentration among the three groups.

CONCLUSIONS

These results suggest that administered 3-OHB may suppress glycolysis during hemorrhagic shock.

Neuroprotection by glial cells through adult T cell leukemia-derived factor/human thioredoxin (ADF/TRX)

Adult T cell leukemia-derived factor (ADF) is a human homologue of thioredoxin (TRX) with many biological functions and is induced by various stimuli and stress. In the central nervous system (CNS), expression of ADF/TRX occurs in glial cells during ischemia and reperfusion. We showed that ADF/TRX was actively released from U251 astrocytoma cells upon exposure to a low concentration of H2O2. The addition of conditioned medium from H2O2-stimulated U251 cells or recombinant ADF (rADF) to the culture medium promoted the survival of neurons from embryonic mouse cortex and striatum, but the addition of mutant ADF (mADF), which has no reducing activity, did not. In addition to rADF, incubation with two other thiol compounds, 2-mercaptoethanol (2-ME) and N-acetyl-L-cysteine (NAC), also increased the neuronal cell survival rate. In contrast, L-buthionine-(S,R)-sulfoximine (BSO), which inhibited the synthesis of glutathione (GSH), decreased the neuronal cell survival rate. Intracellular GSH was increased by incubation with rADF for 24 h, as it is with 2-ME and NAC. Redox active molecules such as thiol compounds may be survival factors for central neurons in vitro, and this capacity may be supplied by endogenous molecules, such as ADF/TRX and glutathione, under certain pathologic conditions in vivo.

Nitric oxide-related inhibition of carotid chemosensory nerve activity in the cat

The hypothesis that endogenous nitric oxide may play a physiological role in the regulation of carotid chemosensory activity was tested in this study. The nitric oxide synthase (NOS) inhibitors, L-nitro-arginine-methyl ester (L-NAME, 25-200 microM) and NG-monomethyl-L-arginine acetate (L-NMMA, 50 and 100 microM) were used to study its effects on the chemosensory activity of perfused and superfused cat carotid bodies (n = 21) in vitro at 37-37 degrees C. L-NAME elicited slow excitation of the sensory activity as did L-NMMA. The peak-response was dose-dependent, and approached saturation around 200 microM. The excitation by L-NAME showed the following characteristics (mean +/- SEM): latency of response, 2.2 min +/- 0.3 min; time to peak response, 5.5 min +/- 1.0 min and the peak response increased to 407 +/- 42 imp/sec from 88 +/- 13 imp/sec. The peak response was significantly different (P < 0.05) from the baseline activity. L-arginine (50-500 microM) only briefly reversed the stimulation. Hypoxia enhanced the excitation by L-NAME. On the other hand, sodium nitroprusside (SNP, 0.5-10 microM) which supplies NO, terminated the excitatory effect of L-NAME. The results provide evidence in favor of an inhibitory role of endogenous NO in the carotid body, and exogenous application of NO confirms the inhibitory effect.