[Molluscicidal effect of suspension concentrate of niclosamide ethanolamine salt]

Objective To evaluate the molluscicidal effect of suspension concentrate of niclosamide ethanolamine salt (SCNE) against Oncomelania hupensis snails in laboratory and field. Methods The experiment of SCNE against the snails by using the immersing and spraying methods was performed in laboratory and field, with control groups of wettable powder of niclosamide ethanolamine salt (WPN). Results In the laboratory, LC_50(s) of SCNE for 24, 48 h and 72 h by using the immersion method were 0.092 6, 0.062 9 mg/L and 0.054 9 mg/L, respectively. The mortality rates of snails for 24, 48 h and 72 h by using the immersion method were all 100% with the concentrations of 0.25 mg/L. The mortality rates of snails were all 100% while spraying SCNE for 3 d in the laboratory with the concentrations of 0.25 g/m². In Jiangling County, except 0.5 g/m³ SCNE immersing the snails for 24 h, the mortality rates of snails by using SCNE with the immersing method were all 100%. While the concentration of SCNE was 0.5 g/m³ or above, the mortality rates were all 100% after the use of it with the immersion method for 2 d in Gong'an County. In Jiangling County, the mortality rates of snails by using SCNE 0.5 g/m³ for 1 d, 3 d, and 7 d with the spraying method were 87.5%, 92.82% and 97.40% respectively. While the concentration of SCNE was 0.5 g/m³, the mortality rates were 85.94%, 86.78% and 94.21% respectively after the use of it with the spraying method for 1 d, 3 d, 7 d in Gong'an County, and the molluscicidal effect of SCNE (1.0 g/m²) was higher than that of WPN. Conclusion SCNE has a high molluscicidal effect in the laboratory and field, and it is a novel and simple formulation of niclosamide.

Double-antigen sandwich ELISA for detection of antibodies to SARS-associated coronavirus in human serum

The study presented here was conducted to evaluate the performance of a double-antigen sandwich ELISA to detect antibodies in human serum against the coronavirus associated with severe acute respiratory syndrome (SARS). A recombinant partial nucleocapsid protein of SARS-associated coronavirus was used as a serodiagnostic antigen in the ELISA. A total of 2892 clinical serum samples were tested with the ELISA kit, which positively identified 25 of 35 (71.4%) samples of patients with confirmed SARS infection, 286 of 407 (70%) samples of patients suspected of having SARS, 229 of 302 (75.8%) samples of convalescent SARS patients, and 0 of 544 samples obtained from healthcare workers; only 1 of 1604 clinical samples obtained from patients with other diseases demonstrated a weakly positive result. These results indicate that the double-antigen sandwich ELISA is an effective screening method for the serodiagnosis of SARS-associated coronavirus.

Tumour necrosis factor alpha impairs function of liver derived T lymphocytes and natural killer cells in patients with primary sclerosing cholangitis

BACKGROUND

Primary sclerosing cholangitis (PSC) is considered to be a chronic autoimmune disease where infiltrating T lymphocytes have been implicated in the destruction of bile ducts. Altered function of these T cells may reflect abnormalities in the immune response leading to tissue damage.

AIM

We investigated the proliferative and functional capacity of freshly isolated liver derived T lymphocytes (LDLs) and natural killer (NK) cells from PSC patients.

METHODS

The proliferative responses to common mitogens such as phytohaemagglutinin (PHA), concanavalin A (Con A), and lipopolysaccharide (LPS) were studied, and the cytotoxic function of T lymphocytes was measured using allogeneic target cells. NK (CD56(+)/16(+)) cytotoxic function was measured using the two cell lines K562 (NK sensitive) and Raji lymphoma cells (NK resistant).

RESULTS

Compared with patients with primary biliary cirrhosis (PBC), autoimmune hepatitis (AIH), and normal controls (without liver disease), in PSC: (1) LDLs contained a low percentage of T cells; (2) there was significantly decreased expression of interleukin (IL)-2 receptor (p<0.001) on activated T cells (HLA-DR(+)); (3) LDLs but not peripheral blood lymphocytes had significantly impaired proliferative responses to mitogens such as PHA, Con A, and LPS (p< 0.001); (4) no cytotoxic activity of PSC liver T and NK cells was recorded; (5) significantly higher levels of tumour necrosis factor alpha (TNF-alpha) and IL-1beta but lower levels of IL-2, IL-10, and interferon gamma were found in the supernatants of mitogen stimulated LDL cultures (p<0.001); (6) higher percentages of freshly isolated PSC LDLs contained intracytoplasmic TNF-alpha and IL-1beta; and (7) pretreatment of PSC LDLs in vitro with neutralising TNF antibodies significantly enhanced proliferative responses and allowed IL-2 receptor expression following stimulation. In addition, the impaired cytolytic activity of both NK and T cells was partially restored. Impaired proliferative or functional capacity of liver derived T cells was not observed in either PBC or AIH patients.

CONCLUSIONS

We suggest that reduced T cell reactivity in liver infiltrating cells obtained from patients with PSC is due to high local production of TNF-alpha. Our findings indicate that the use of anti-TNF antibodies as an alternative treatment for PSC patients should be evaluated.

Molecular cloning and characterization of a novel ATP P2X receptor subtype from embryonic chick skeletal muscle

We have cloned a new P2X ligand-gated ion channel receptor from embryonic chick skeletal muscle, which is tentatively named as chick P2X(8) (cP2X(8)) receptor. The cloned cDNA encodes a protein with 402 amino acids. Electrophysiological study of the recombinant cP2X(8) receptor expressed in Xenopus oocytes showed that 10 microm ATP induced a fast inward current followed by rapid and long lasting desensitization in medium containing 1.8 mm Ca(2+). In medium with 0. 3 mm Ca(2+) ATP induced a bi-phasic response as follows: a slower inward current succeeded the initial fast one. 2-Methylthio-ATP, alpha,beta-methylene-ATP, and adenosine 5'-O-(thio)triphosphate were potent agonists, whereas ADP was a very weak agonist. ATP-induced currents were blocked by 100 microm suramin and pyridoxal phosphate 6-azophenyl-2',4'-disulfonic acid. Northern blot analysis and reverse transcription-polymerase chain reaction showed that cP2X(8) RNA transcripts were mainly expressed in skeletal muscle, brain, and heart of Day 10 chick embryos. A moderate level of expression was also detected in gizzard and retina. Whole mount in situ hybridization showed that cP2X(8) RNA transcripts were expressed mainly in neurotube, notochord, and stomach in Day 3 embryos. In Day 4 and Day 6 embryos, the cP2X(8) RNA transcripts were highly expressed in the myotome and premuscle mass. The physiological role of this receptor in the establishment of the skeletal muscle innervation will be studied.

Impact of respiratory movement on the computed tomographic images of small lung tumors in three-dimensional (3D) radiotherapy

PURPOSE

Three-dimensional (3D) treatment planning has often been performed while patients breathe freely, under the assumption that the computed tomography (CT) images represent the average position of the tumor. We investigated the impact of respiratory movement on the free-breathing CT images of small lung tumors using sequential CT scanning at the same table position.

METHODS

Using a preparatory free-breathing CT scan, the patient's couch was fixed at the position where each tumor showed its maximum diameter on image. For 16 tumors, over 20 sequential CT images were taken every 2 s, with a 1-s acquisition time occurring during free breathing. For each tumor, the distance between the surface of the CT table and the posterior border of the tumor was measured to determine whether the edge of the tumor was sufficiently included in the planning target volume (PTV) during normal breathing.

RESULTS

In the sequential CT scanning, the tumor itself was not visible in the examination slice in 21% (75/357) of cases. There were statistically significant differences between lower lobe tumors (39.4%, 71/180) and upper lobe tumors (0%, 0/89) (p < 0.01) and between lower lobe tumors and middle lobe tumor (8.9%, 4/45) (p < 0.01) in the incidence of the disappearance of the tumor from the image. The mean difference between the maximum and minimum distances between the surface of the CT table and the posterior border of the tumor was 6.4 mm (range 2.1-24.4).

CONCLUSION

Three-dimensional treatment planning for lung carcinoma would significantly underdose many lesions, especially those in the lower lobe. The excess "safety margin" might call into question any additional benefit of 3D treatment. More work is required to determine how to control respiratory movement.

Localization of ATP-gated P2X2 and P2X3 receptor immunoreactive nerves in rat taste buds

P2X receptors have been suggested to play a role in the transduction of sensory signals such as pain and sound. In the present study, polyclonal antibodies against P2X1 to P2X6 receptors were used to localize P2X receptors in circumvallate and fungiform papillae of rats. Nerve fibres innervating the taste buds stained intensely with P2X3 receptor antibodies. P2X3 receptor-positive nerves were observed in the intra- and subgemmal regions. The nerve fibres were also stained with P2X2 receptor antibodies, but the intensity was much lower. The distribution of P2X2 receptor immunoreactivity overlaps with that of P2X3. These results suggest that ATP might be a neurotransmitter in taste reception cells in the taste buds, where it transducts the taste signals to the afferent taste nerves by activating P2X receptors at the synapses. This is the first experiment indicating such a role for ATP, although supplementary functional studies are required.

P2X receptor immunoreactivity in the rat cochlea, vestibular ganglion and cochlear nucleus

P2X receptors have been reported to be involved in neurotransmission in both central and peripheral nerves. In the present study, polyclonal antibodies against P2X1, P2X2, P2X3, P2X4, P2X5, and P2X6 were used to study the distribution of P2X receptors in rat cochlea and vestibulocochlear nerve pathways. It was found that in the vestibular ganglion all six types of antibodies stained the neurons to different intensities. The strongest signal was obtained with the P2X2 antibodies, followed by P2X3 antibodies. The other four antibodies produced weak signals, of approximately the same intensity. In the spiral ganglion, the six types of antibodies also stained almost all neurons. However, the rank order of intensity was different from that in the vestibular ganglion: the strongest signal was still obtained with P2X2 antibodies, followed by P2X4, P2X1, and P2X3 antibodies. The immunolabelling was much weaker with P2X5, and P2X6 antibodies compared with the other four types of antibodies. In the cochlea, besides the spiral ganglion neurons, other tissues such as stria vascularis, the organ of Corti and the tectorial membrane were labelled intensively with P2X2 antibodies only. High density P2X2 immunoreactivity was also observed in the vestibulocochlear nerve fibres. In the cochlear nucleus, neurons and nerve fibres were stained with the P2X2 antibodies, as were the neurons in the trapezoid body. These results suggested that P2 receptors, especially the P2X2 receptors, may play important roles in the signal transduction involved in the perception of sound and balance.

Localization of ATP-gated P2X2 receptor immunoreactivity in the rat hypothalamus

Previous pharmacological studies have indicated that ATP receptors may be involved in the regulation of physiological functions in hypothalamus. In the present study, the distribution of P2X2 receptor in the rat hypothalamus was studied with immunohistochemistry. It was shown that P2X2 immunoreactivity-positive neurons and nerve fibres were localized in many hypothalamic nuclei. Intense labelling of both neuronal cell bodies and nerve fibres was observed in the paraventricular nucleus, arcuate nucleus, retrochiasmatic area, periventricular nucleus, and the ventral part of tuber cinereum area. In supraoptic, circular, and ventral tuberomammillary nuclei the neuronal cell bodies were strongly positive, but few nerve fibres were positive. Axons with strong P2X2 immunoreactivity were found in the organum vasculosum of the lamina terminalis and median eminence. Some scattered positive neurons and nerve fibres were found in many hypothalamic nuclei including preoptic nucleus. The results of the present study demonstrated the existence of P2X receptors in hypothalamus, as a basis for detailed studies of the roles of P2X receptors in the regulation of hypothalamic functions.

Localization of ATP-gated P2X receptor immunoreactivity in rat sensory and sympathetic ganglia

The distribution of P2X1, P2X2, P2X3, P2X4, P2X5 and P2X6 receptors, a family of ATP-gated cation channels, in rat trigeminal, dorsal root, nodose, superior cervical, and coeliac ganglia was studied immunohistochemically. It was found that polyclonal antibodies for the six P2X receptor subtypes could label over 90% of neurones in these ganglia to different intensities. There was also considerable variation in intensity of immunoreactivity in individual neurones within each ganglion. In dorsal root and trigeminal ganglia expression of the P2X3 receptor was much higher than for the other five subtypes. P2X3 immunoreactivity was much more intense in the small-diameter neurones than in the large-diameter neurones. In nodose ganglion, both P2X2 and P2X3 antibodies labelled the neurones intensely. In sympathetic superior cervical and coeliac ganglia, immunoreactivity to five P2X receptor subtypes were detected (exception, P2X5), with P2X2, P2X4 and P2X6 showing higher intensity. Low level expression of P2X3 receptor in sympathetic ganglia indicates that this receptor subtype is not limited to the sensory ganglia where it was highly expressed. The results have demonstrated that both sensory and sympathetic ganglia express a variety of P2X receptor subtypes and that different subtypes are expressed to different levels and by different subpopulations of neurones.

Pharmacological and molecular characterization of P2X receptors in rat pelvic ganglion neurons

1. The presence and characteristics of P2X receptors on neurons of the rat major pelvic ganglia (MPG) have been studied using whole cell voltage-clamp, in situ hybridization and immunohistochemistry. 2. Rapid application of ATP (100 microM) to isolated rat MPG neurons induced moderately large inward currents (0.33-5.3 nA) in 39% of cells (108/277). The response to ATP occurred very rapidly, with an increase in membrane conductance, and desensitized slowly. 3. The concentration-response curve for ATP yielded an EC50 of 58.9 microM. The agonist profile was ATP> or =2MeSATP=ATPgammaS>BzATP, while alpha,beta-MeATP, beta,gamma-MeATP, UTP and ADP were all inactive at concentrations up to 100 microM. 4. The response to ATP was antagonized by suramin (pA2=5.6), reactive blue-2 (IC50=0.7 microM) and pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS). 5. Lowering the pH from 7.4 to 6.8 produced a marked potentiation (to 339% of control) of the responses to ATP (30 microM), while raising the pH to 8.0 attenuated the responses (to 20% of control). The EC50s for ATP were 28.8, 58.9 and 264 microM at pH 6.8, 7.4 and 8.0, respectively. 6. Co-application of ATP with Zn2+ produced a marked enhancement of the responses to ATP, with an EC50 of 9.55 microM. In the presence of Zn2+ (30 microM), the EC50 for ATP was decreased to 4.57 microM. 7. In situ hybridization revealed that the P2X receptor transcripts levels in rat MPG neurons are P2X2>P2X4>P2X1, P2X3, P2X5 and P2X6. The immunohistochemical staining revealed a small number of neurons with strong P2X2 immunoreactivity. 8. In conclusion, our results indicate that there are P2X receptors present on MPG neurons. The pharmacological characteristics of these receptors, the in situ hybridization and immunohistochemical evidence are consistent with them being of the P2X2 subtype, or heteromultimers. with P2X2 being the dominant component.

A comparative observation on treatment of heart failure due to diastolic insufficiency of the left ventricle--a report of 43 cases

43 cases of heart failure due to diastolic insufficiency of the left ventricle were treated with TCM differential treatment as the treatment group, the total effective rate being 86.0%. Statistically significant difference (P < 0.05) in the therapeutic effects was found between the treatment group and control (25 cases) group. Improvement of the left ventricular diastole in the treatment group was more obvious than that of the control group (P < 0.01), while contractility of the left ventricle was also improved to a certain extent.

Pharmacological and histochemical evidence for P2X receptors in human umbilical vessels

The presence of P2X purinoceptors in human umbilical vessels were studied with organ bath recording, radioligand binding assays, autoradiography, and immunohistochemistry. In isolated umbilical arteries and veins from normal term pregnancy, both ATP and alpha,beta-methylene ATP caused concentration-dependent contractions. ATP-induced responses were blocked by desensitisation with alpha,betamethylene ATP. However, both the ATP- and alpha,beta-methylene ATP-induced responses were not antagonised by suramin. No significant difference in responses was observed in the vessels with or without endothelial cells. Radioligand binding assays using [3H]alpha,beta-methylene ATP showed the presence of a population of high-affinity binding sites in both the arteries and veins. The Kd values of the binding sites were 2.77 + 1.10 nM for the arteries, and 3.23+/-1.22 nM for the veins. The maximum binding site densities were 634+/-237 and 947+/-308 fmol/mg protein for the arteries and the veins, respectively. Autoradiographic localisation with [3H]alpha,beta-methylene ATP demonstrated that the specific binding sites were only distributed over the smooth muscle cells of the vessels. Immunohistochemical studies with specific polyclonal antibodies against P2X1-6 receptors showed that positive immunostaining was also restricted to smooth muscle cells. Antibodies against P2X1 receptors produced the strongest signals, while antibodies against the other five P2X subtypes produced much weaker signals. The results in the present study indicate the existence of P2X purinoceptors in the smooth muscle of human umbilical vessels. Their physiological functions remain to be studied.

Inhibition of fibroblast-like cell proliferation by interleukin-1 blockers, CK-119 and CK-122

AIM

To study potent and nontoxic agents to inhibit fibroblast proliferation.

METHODS

Fibroblast-like corneal and conjunctival cells were cultured and inhibited by interleukin-1 (IL-1) blockers, dihydropyridazino-pyridazines CK-119 and CK-122. The cell growth and syntheses of DNA, RNA, and protein after IL-1 blocker incubation were determined.

RESULTS

CK-119 and CK-122 inhibited cell growth of corneal fibroblast at 30 mg.L-1. DNA and RNA syntheses in corneal fibroblasts were markedly inhibited by CK-119 and CK-122 whereas protein synthesis was either unaffected or mostly enhanced at 30-100 mg.L-1 and 100-300 mg.L-1, respectively. Similar results were obtained in conjunctival cell cultures by CK-119 and CK-122 at 3-10 mg.L-1 and 30-100 mg.L-1, respectively.

CONCLUSION

CK-119 and CK-122 are potent IL-1 blockers to inhibit cell growth of fibroblast-like corneal and conjunctival cells mainly through the inhibition of DNA and RNA syntheses but not protein synthesis.

Coexpression of mRNAs for P2X1, P2X2 and P2X4 receptors in rat vascular smooth muscle: an in situ hybridization and RT-PCR study

The expression of mRNAs for three P2X receptor subtypes (PX21, P2X2, P2X4) in the rat vascular system was studied by in situ hybridization and RT-PCR. In heart sections mRNAs transcripts for all three receptors were colocalized in smooth muscle cells of coronary vessels, while no specific positivity was apparent in myocardium. Coexpression of P2X receptor mRNA transcripts were also observed in other peripheral vessels, including aorta, pulmonary artery, internal and external iliac arteries, renal artery and femoral artery. By contrast, no mRNA transcripts of the above receptors were found in the superior mesenteric artery. RT-PCR performed on microdissected tissues (coronary arteries, aorta and myocardium from various heart areas) confirmed the presence of P2X1, P2X2 and P2X4 receptor mRNAs. Furthermore, in the same tissues two splice variants of the P2X2 receptor were identified. These results reveal an important molecular heterogeneity of P2X receptors, thus substantiating the possibility of a heteropolymeric assembly of ATP-gated ion channels in the cardiovascular system.

P2X purinoceptors in postmortem human cerebral arteries

Pharmacological studies have demonstrated that various purinoceptors are involved in the control of the cerebral vascular tone in many species. In this study, the existence of P2X purinoceptors in the postmortem human cerebral arteries was investigated with organ-bath pharmacology, autoradiography, and immunohistochemistry. Specimens were obtained from the M2 region of the middle cerebral arteries from human cadavers with an age range of 53-91 years and postmortem time of 37-54 h. Application of alpha,beta-methylene adenosine triphosphate (ATP) produced concentration-dependent contraction in the arterial ring, whereas transmural nerve stimulation and noradrenaline did not elicit contraction. Autoradiography using [3H]alpha,beta-methylene ATP (a radioligand for P2X purinoceptors) showed specific [3H]alpha,beta-methylene ATP binding sites in the smooth-muscle cells of the postmortem human cerebral arteries. Immunohistochemistry with specific P2X1 purinoceptor antibodies revealed positive staining exclusively in the smooth muscle of the same specimens. All these results demonstrate the existence of P2X purinoceptors in human cerebral arteries, which were still functionally active despite the long postmortem time. The results from this study suggest that the postmortem human cerebral arteries can be useful specimens for studying the P2X purinoceptor-mediated responses.

P2Y purinoceptors in gastric gland plasma membranes

This autoradiographic study of sections of the rabbit stomach fundus labelled with [35S]dATP alpha S, a radioligand for P2Y purinoceptors, has demonstrated a discrete pattern of distribution of the binding sites, i.e., the specific binding was only over the mucosa, but not over the muscular layer. Radioligand binding assays carried out on gastric gland plasma membranes showed that the binding process was saturable and a high density of a homogeneous population of binding sites was observed. These binding sites presented high affinity with a value of Kd = 4.1 +/- 0.8 nM and the maximum density of the binding sites was 16.8 +/- 1.6 pmol/mg protein. The displacement by purinoceptor ligands showed the following order of potency: ATP = 2-methylthio ATP > > alpha, beta-methylene ATP > > adenosine. Neither UTP nor pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS) were able to displace the binding. The data support the presence of P2Y purinceptors in rabbit gastric glands.

Clinical application of the computer picture archiving and communicating system to stereotactic radiosurgery

Stereotactic radiosurgery, a rapidly evolving technology, provides precise high-dose irradiation to brain lesions and tumors. A new method using digital subtraction angiographic images of a personal computer-image display terminal interfaced to our picture archiving and communication system (PACS) performs measurements and calculations of the coordinates of the location of the center of the lesion to be treated. The time required to calculate the coordinates was performed by three methods: hand calculation, digitizer method, and PACS method. These three coordinates were compared in 10 cases. The hand calculation method required approximately 50 minutes, the digitizer method required approximately 10 minutes, and the PACS method approximately 3 minutes. The difference is statistically significant (P < .001). The three methods were equally accurate. This type of PACS application using inexpensive personal computers interfaced more directly to a PACS is an emerging trend that facilitates wider access to images and to manipulating them for specialized applications.

P2X purinoceptors in the feline pulmonary vascular bed: distribution and selective in vivo pharmacological probes

The distribution and identification of selective pharmacological probes for P2X purinoceptors in the pulmonary vascular (PV) bed of the cat have been investigated with autoradiographic and pharmacological techniques. Autoradiographic localization of the selective P2X purinoceptor ligand alpha, beta-[3H]methylene ATP (alpha, beta-MeATP) binding sites in cat lung shows that P2X purinoceptors are present in all vessels in the bed; high densities were present in large (2-mm diam) and small (0.5-mm diam) pulmonary arteries, bronchial arterioles (0.1-mm diam), and large pulmonary veins, whereas low density is characteristic of parenchymal arterioles and alveolar walls. Most of the binding is displaced with the P2X-purinoceptor agonist beta, gamma-methylene ATP and the putative selective P2X-purinoceptor antagonist pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS) in all vessels; however, the binding is further displaced with the, P2Y-purinoceptor agonist 2-methylthio ATP (2-MeS-ATP), which suggests the presence of P2Y as well as P2X purinoceptors. P2X purinoceptors mediate potent vasoconstrictor actions in the PV bed. alpha, beta-MeATP is a selective agonist for P2X purinoceptors and does not act via serotonergic, histaminergic, adrenergic, or leukotriene vasoconstrictor receptors to produce an increase in PV resistance. The vasoconstrictor responses of alpha, beta-MeATP are attenuated by PPADS. However, PPADS has no effect on the vasodilation induced by ATP, adenosine, or 2-MeS-ATP. The diadenosine nucleotide AP5A also produced dose-dependent vasoconstrictor responses of the PV bed, which were approximately three times less potent than those of alpha, beta-MeATP and significantly reduced by PPADS. These data support that vasoconstrictor P2X purinoceptors are present on pulmonary vessels. The functional significance of these vascular P2X purinoceptors in the PV bed is not known; however, alpha, beta-MeATP, AP5A, and PPADS may be used in vivo to define their physiological role in health and disease in the lung.

Distribution of [3H] alpha, beta-methylene ATP binding sites in pulmonary blood vessels of different species

Purinergic neurotransmission has been reported to take part in the regulation of pulmonary vascular resistance in many species. The receptor which mediates the contraction of blood vessels by ATP was defined as P2X-purinoceptors in pharmacological studies. In the present study, autoradiographic localization of P2X-purinoceptors was carried out in pulmonary blood vessels from rat, guinea-pig, rabbit, piglet and human by using [3H] alpha, beta-methylene ATP ([3H] alpha, beta-MeATP) as the radioligand. Autoradiographs showed that all the pulmonary arteries had been labelled with [3H] alpha, beta-MeATP. The specific binding sites were only associated with the smooth muscle of the blood vessels. Semi-quantitation of the autoradiographs revealed significant differences in the densities of P2X-purinoceptors amongst the vessels studied, both regional and interspecific. Generally, intrapulmonary arteries were labelled more heavily than the main pulmonary arteries, and the medium- and small-sized arteries had higher densities of P2X-purinoceptor than the large muscular arteries. The veins were sparsely labelled, except that rat intrapulmonary veins were labelled moderately. The results from this study provide: (1) direct evidence for the existence of P2X-purinoceptors in pulmonary vasculature, (2) a semi-quantitative estimation of the relative density of P2X-purinoceptors in pulmonary vessels of different sizes; and (3) a comparison of the P2X-purinoceptor densities among the species studied. Furthermore, the distribution of the P2X-purinoceptors is consistent with known pharmacological responses elicited by ATP in these vessels.

Characterization and autoradiographic localization of [3H] alpha,beta-methylene ATP binding sites in cat urinary bladder

1. The characteristics and distribution of [3H] alpha,beta-methylene ATP ([3H] alpha,beta-MeATP), a radioligand for P2X-purinoceptors, binding sites in cat urinary bladder detrusor were examined. 2. Saturation analysis revealed that, in cat bladder membrane preparations, only one population of binding sites with high affinity (Kd = 1.8 nM) was present, in contrast to other species where both high-and low-affinity binding sites are present. Another feature is that the density of the binding sites in the cat bladder (Bmax = 21.2 pmol/mg protein) is considerably higher (about 2-fold) than the high-affinity binding component in the rat bladder membrane preparations. 3. Displacement experiments with unlabelled purinoceptor ligands indicate that [3H] alpha,beta-MeATP mainly binds to P2X-purinoceptors. The order of binding displacement activity was: alpha,beta-methylene ATP, beta,gamma-methylene ATP > 2-methylthioATP > ATP > suramin and L-beta,gamma-methylene ATP > > adenosine. 4. Autoradiographic study demonstrated dense specific binding sites of [3H] alpha,beta-MeATP on detrusor smooth muscle of cat bladder. 5. The results of this study are consistent with pharmacological studies for the existence of P2X-purinoceptors in cat bladder.

A P2X purinoceptor cDNA conferring a novel pharmacological profile

We have cloned P2X4, a member of the P2-purinoceptor family, which has a new pharmacological profile. Rat P2X4 is distantly related to P2X1, P2X2 and P2X3 and is expressed in brain, spinal cord, lung, thymus, bladder, adrenal, testis and vas deferens. This ligand gated ion channel is activated by ATP and analogs with the potency order of ATP > ATP gamma S > 2-methylthio ATP > ADP approximately alpha beta-methylene ATP. However, none of the currently used P2X purinoceptor antagonists suramin, reactive blue 2 and PPADS blocked ATP evoked currents; in contrast their application resulted in potentiation of the agonist response. Due to lack of any known antagonist for P2X4 it is unlikely that native P2X4 has previously been recognized as a P2X purinoceptor.

Characterization and autoradiographic localization of [3H] alpha, beta-methylene adenosine 5'-triphosphate binding sites in human urinary bladder

OBJECTIVES

To characterize [3H] alpha, beta-methylene adenosine 5'-triphosphate ([3H] alpha, beta-MeATP, a radioligand for P2x-purinoceptors) binding sites in the washed homogenates and membrane preparations of human urinary bladder and, using autoradiography, to localize [3H] alpha, beta-MeATP binding sites in human bladder.

MATERIALS AND METHODS

Specimens were obtained from the fundus of the urinary bladder of male patients aged 56-79 years. The washed homogenates or membrane preparations of the bladder specimens were incubated with [3H] alpha, beta-MeATP and the bound and free radioligand separated by filtration. For autoradiography, cryostat sections were incubated with 10 nM [3H] alpha, beta-MeATP, washed, dried and exposed for 2 weeks to emulsion-coated coverslips. In both experiments, 100 microM beta, gamma-methylene ATP was used to determine non-specific binding.

RESULTS

Six of 16 specimens in the binding assay and three of seven specimens in the localization study showed specific [3H] alpha, beta-MeATP binding. The binding process was saturable and the specific binding sites were composed of a high- and low-affinity component. The specific binding to membrane preparations was reduced in the presence of Mg2+ in the incubation medium. Competitive displacement experiments showed that the order of potency of the unlabelled ligands to displace the [3H] alpha, beta-MeATP binding was alpha, beta-methylene ATP > beta, gamma-methylene ATP > suramin > 2-methylthio ATP > ATP > ADP >> adenosine, which indicates that the binding sites are, or are linked to, P2x-purinoceptors. Autoradiography showed that the specific [3H] alpha, beta-MeATP binding sites were located only over the smooth muscle of the bladder.

CONCLUSIONS

The results suggest that P2x-purinoceptors exist in human urinary bladder, although at a lower density than reported for rodent urinary bladder.

Autoradiographic labelling of P2 purinoceptors in the guinea-pig cochlea

Two different radioligands were used to identify extracellular ATP binding sites specific to P2 purinoceptors in guinea-pig cochlear tissue. Deoxyadenosine 5'-(alpha-[35S]thio)triphosphate ([35S]dATP alpha S; 10 nM) provided a high activity probe for the P2y purinoceptor subtype on the basis of selective block by 2-methylthio-ATP (2MeSATP; 100 microM). [3H]alpha, beta-methylene-ATP (10 nM), a high affinity probe for a P2x purinoceptor subtype was selectively blocked by inclusion of the related compound beta, gamma-methylene-ATP (100 microM). Both probes labelled the organ of Corti, stria vascularis and spiral prominence regions. The P2x purinoceptor probe also bound to lateral wall tissue below the spiral prominence and insertion point of the basilar membrane within the scala tympani compartment, a region which failed to show significant binding using [35S]dATP alpha S. Frozen sections of whole cochlea permitted analysis of radioligand binding to the cell body region (spiral ganglion in Rosenthal's canal) of the primary auditory afferents and the auditory nerve itself, which lies within the central region of the modiolus of the cochlea. Both these regions exhibited 2MeSATP blockable [35S]dATP alpha S binding whereas specific [3H]alpha, beta-methylene-ATP binding was absent from spiral ganglion and minimal in the auditory nerve region. These results demonstrate a mixed P2 purinoceptor distribution in cochlear tissues and suggest that complex purine-mediated neurohumoral mechanisms may influence cochlear function at a number of sites.

Distribution of [3H]alpha,beta-methylene ATP binding sites in rat brain and spinal cord

The distribution of [3H]alpha,beta-methylene ATP ([3H]alpha,beta-MeATP) binding sites in rat brain and spinal cord was examined using autoradiography. It was shown that many structures in the CNS are densely labelled, and that the binding is displaced by both beta,gamma-methylene ATP and the P2X-purinoceptor antagonist, pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), indicating that the binding sites are P2X-purinoceptors. Image analysis revealed that the nuclei of the thalamus have the highest density of labelling. Other densely labelled structures include: the amygdaloid, substantia nigra, cerebral cortex, hypothalamus, caudate putamen, geniculate nuclei, medial habenula and the intermediate zone of grey matter in the spinal cord. These results are consistent with the limited amount of electrophysiological evidence for the existence of P2X-purinoceptors in the CNS, and provoke the need for extensive physiological studies to establish the roles of P2X-purinoceptors in the CNS.

Comparative studies on the affinities of ATP derivatives for P2x-purinoceptors in rat urinary bladder

1. Radioligand binding assays have been used to determine the affinities of a series of ATP derivatives with modifications of the polyphosphate chain, adenine and ribose moieties of the ATP molecule for [H]-alpha,beta-methylene ATP ([3H]-alpha,beta-MeATP) binding sites in rat urinary bladder. 2. The replacement of the bridging oxygen in the triphosphate chain of ATP (pIC50 = 5.58) with a methylene or imido group markedly increased the affinity (691 fold in IC50 values for beta,gamma-imidoATP, 15 fold for beta,gamma-methylene ATP), and the replacement of an ionized oxygen on the gamma-phosphate with a sulphur (ATP gamma S) also led to increased affinity (5623 fold in IC50 values). 3. Modifications at N6, N1, and C-8 positions on the purine base usually reduced the affinity of ATP (a decrease of 2.8 fold in IC50 values for N6-methylATP and 8.9 fold for 8-bromo ATP), while the attachment of an alkylthio group to the C-2 position greatly increased the affinity for P2x-purinoceptors (from 3.5 to 98 fold increase in IC50 values). 4. Replacement of the 3'-hydroxyl group on the ribose with substituted amino or acylamino groups produced more potent P2x-purinoceptor agonists (an increase of 447 fold in IC50 values for 3'-deoxy-3'-benzylamino ATP and 28 fold for 3'-deoxy-3'-(4-hydroxyphenylpropionyl)amino ATP. 5. Diadenosine polyphosphates (Ap[n]A) were also shown to displace the [3H]-alpha,beta-MeATP binding. The rank order of potency was Ap6A > Ap5A > Ap4A >> Ap3A >> Ap2A. 6. Suramin, PPADS, and reactive blue 2 could competitively displace the binding of [3H]-alpha,beta-MeATP toP2X-purinoceptors, with pIC50 values of 6.26, 5.35, and 6.22, respectively.

PPADS selectively antagonizes P2X-purinoceptor-mediated responses in the rabbit urinary bladder

1. Pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS), an inhibitor of P2X-purinoceptor-mediated responses in rabbit vas deferens, was investigated for its ability to antagonize contractions evoked by alpha,beta-methylene ATP (alpha,beta-MeATP), carbachol and electrical field stimulation in the rabbit urinary bladder detrusor muscle. 2. PPADS. (1-30 microM) caused concentration-dependent inhibition of contractions to the stable P2X-purinoceptor agonist, alpha,beta-MeATP, decreasing the maximum response to alpha,beta-MeATP (30 microM) at concentrations of 3-30 microM. The pD2 value for alpha,beta-MeATP in the absence of PPADS was 6.52 +/- 0.10 (8). In the presence of PPADS at concentrations of 1, 3, 10 and 30 microM the negative log concentrations of alpha,beta-MeATP that cause the same contractile response as the pD2 value were significantly different from control, being respectively 6.17 +/- 0.09 (8), 5.64 +/- 0.12 (7), 5.15 +/- 0.23 (7) and 4.78 +/- 0.22 (5). 3. PPADS (1-30 microM) caused concentration-dependent inhibition of contractions to stimulation of intramural purinergic nerves (1-32 Hz). There was a greater inhibition at lower frequencies (1-8 Hz) than at higher frequencies (16-32 Hz). PPADS, 30 microM, did not produce significantly greater antagonism than 10 microM. 4. PPADS (30 microM) had no significant influence on the contractile potency of carbachol: the pD2 values of carbachol in the absence and presence of PPADS were not significantly different being 6.42 +/- 0.16 (5) and 6.33 +/- 0.18 (5), respectively. However, PPADS caused a small, but significant, suppression of the maximal response of carbachol, reducing it by approximately 9%. 5. Radioligand binding studies carried out on rabbit bladder membranes with [3H]-alpha,beta-methylene ATP([3H]-alpha,beta-MeATP) showed that PPADS concentration-dependently inhibited the binding of [3H]-alpha,beta-MeATP to P2X-purinoceptors, while the binding of [3H]-quinuclidinyl benzilate to muscarinic cholinoceptors was not affected.6. Thus, PPADS (1-30 microM) antagonized responses mediated via P2X-purinoceptors in the rabbit urinary bladder. It was selective for P2-purinoceptor-mediated contractions rather than those mediated via muscarinic receptors. Binding studies demonstrated that the antagonistic effect of PPADS is via a direct interaction with P2x-purinoceptors.

Triphosphate, the key structure of the ATP molecule responsible for interaction with P2X-purinoceptors

1. A radioligand binding assay was carried out to explore the key structure in molecules of ATP and its analogues responsible for the binding to P2x-purinoceptors. 2. It was found that adenosine, adenine and xanthine had no significant effect on [3H]alpha, beta-methylene ATP binding to membrane fractions prepared from rat urinary bladder, while pentasodium triphosphate and disodium pyrophosphate could effectively displace the binding. Sodium orthophosphate was shown to displace the binding only at much higher concentration. 3. Apart from ATP, several other nucleotides could also fully displace the specific binding, but with potencies lower than that of ATP. 4. The results indicate that the phosphate side chain in molecules of ATP and its analogues is the key structure responsible for the binding to P2x-purinoceptors.

Heterogeneous distribution of [3H]alpha,beta-methylene ATP binding sites in blood vessels

A radioligand binding assay and autoradiographic localisation of P2X-purinoceptors were carried out in several different blood vessels from rat, guinea-pig and rabbit by using [3H]alpha,beta-methylene ATP ([3H]alpha,beta-MeATP) as the radioligand. The radioligand binding assay on rabbit ear artery showed that the binding process was saturable, and a high density of P2X-purinoceptors was observed. Autoradiographic localisation showed that the specific [3H]alpha,beta-MeATP binding sites were only associated with the smooth muscle of the blood vessels. Semi-quantitation of the autoradiographs revealed significant differences in the densities of P2X-purinoceptors amongst the vessels studied. Generally the medium- and small-sized arteries had higher densities of P2X-purinoceptor than the elastic and large muscular arteries. In some large muscular arteries, such as the rabbit carotid, renal, hepatic and mesenteric, the outer region of vessel had a higher density of receptors than the inner region. The veins in this study were sparsely labelled, except portal veins where the longitudinal and circular layers of muscles were found to have different densities of P2X-purinoceptors. The results from this study provide direct evidence for the existence of P2X-purinoceptors in blood vessels; furthermore, the distribution of the P2X-purinoceptors is consistent with known pharmacological responses elicited by ATP in these vessels.

Solubilization and molecular size determination of the P2x purinoceptor from rat vas deferens

Membranes of the rat vas deferens were shown to contain a high density of binding sites for [3H] alpha, beta-methylene ATP ([3H] alpha, beta-MeATP), a ligand selective for the P2X purinoceptor. Analysis demonstrated two classes, of high affinity (Kd = 1.8 nM, Bmax (maximum density) = 9.3 pmol/mg of protein) and of low affinity (Kd = 34 nM, Bmax = 29 pmol/mg of protein). The high affinity [3H] alpha, beta-MeATP binding sites were successfully solubilized with 2% digitonin: the Kd was then 1.6 nM. Both the association and dissociation of the receptor-ligand complex were rapid (half-time for association = 6.5 min). The rank order of potency of purinergic ligands in displacing [3H] alpha, beta-MeATP binding from the solubilized preparation was in accord with the pharmacological criteria for P2X purinoceptors. The receptor-detergent complex was separated by sucrose gradient ultracentrifugation from the ATPase enzymes also present in the preparation. The sedimentation coefficient of the receptor-detergent complex was 12.1 S. It was shown that [3H] alpha, beta-MeATP can function as a photoaffinity labeling reagent upon exposure to ultraviolet light; in the rat vas deferens membranes, it thus became cross-linked in a specific manner to a polypeptide of apparent molecular mass = 62,000 daltons, proposed to be the ligand-binding subunit of the functional P2X purinoceptor.

Species differences in characteristics and distribution of [3H] alpha,beta-methylene ATP binding sites in urinary bladder and urethra of rat, guinea-pig and rabbit

The characteristics and distribution of [3H] alpha,beta-methylene ATP ([3H] alpha,beta-MeATP, a radioligand for P2x-purinoceptors) binding sites in the urinary bladder of rat, guinea-pig and rabbit were examined. Autoradiographic localization of [3H] alpha,beta-MeATP binding sites was also carried out on the urethra of the three species. Receptor binding assay showed that the rat bladder possesses the highest density of specific binding sites, followed by rabbit and guinea-pig bladder. Semi-quantitative analysis of autoradiograms showed that the grain densities in the bladders of rat, guinea pig, and rabbit were parallel to those obtained from receptor binding assay. The grain densities were greatly reduced in the presence of beta,gamma-methylene ATP (beta,gamma-MeATP). No significant specific binding was detected in the smooth muscle of rat and guinea-pig urethra, while a very low level of specific binding was observed in the rabbit urethra. Differences of grain densities in different regions (dome, body, and trigone) of the same bladder were also observed, but they were not as remarkable as those between species. The results of this study demonstrate species differences of P2X-purinoceptor densities in the urinary bladder, which may reflect differing degrees of purinergic neurotransmitter control of the bladder detrusor muscle.