[Reconstruction of TMJ condyle cartilage defects with autogenous free periosteal grafts]

How to reconstruct the damaged articular cartilage has been one of the main subjects in treatment of articular disease for a long time. In this experimental study, fullthickness cartilage defects of 4 mm x 5 mm in size were created in rabbit's TMJ condyle cartiage on the left sides. The autogenous free periosteum were transplanted to the defects by using biological gelatin. Postoperatively, the animals were killed at intervals of 1, 2, 4, 8, 12 and 16 weeks. The regenerative cartilage in the defects were examined by gross appearance and histology. The result showed that mesenchymal cells in the cambium layer of periostum can transform into chondroblasts under the mechanical stress.

Alterations of alpha1-adrenoceptor subtypes in the hearts of thyroxine-treated rats

Alterations in the cardiac alpha1-adrenoceptor and its subtypes in thyroxine-treated rats were studied by means of radioligand binding assays, measurement of contractile response and reverse transcription-polymerase chain reaction (RT-PCR). The results showed that in thyroxine-treated rats the cardiac alpha1-adrenoceptor density (Bmax) was reduced from 51.6 +/- 6.0 fmol/mg in control to 40.9 +/- 3.7 fmol/mg (P<0.01); and the percentage of high affinity sites for 5-methyl-urapidil decreased from 23.3 +/- 2.0% in control to 10.8 +/- 2.0% in thyroxine-treated rats (P<0.05). The data indicated that the high-affinity sites for 5-methyl-urapidil (alpha1A-adrenoceptor) were reduced (from 12.0 to 4.4 fmol/mg), but the low-affinity sites for 5-methyl-urapidil (alpha1B- plus alpha1D-adrenoceptor) were not changed (from 39.6 to 36.5 fmol/mg). RT-PCR showed that steady-state levels of mRNA for alpha1A- and alpha1B-adrenoceptors were decreased, while that for alpha1D-adrenoceptor was raised in thyroxine-treated rats. In the isolated electrically driven left atria the phenylephrine-induced maximal contractions were reduced from 258 +/- 17 mg in control to 188 +/- 24 mg in thyroxine-treated rats (P<0.05). The pA2 values of 5-methyl-urapidil were reduced from 8.89 +/- 0.36 in control to the hyperthyroidism of 7.87 +/- 0.43 in thyroxine-treated rats (P<0.05). Chlorethylclonidine preincubation shifted concentration-response curves for phenylephrine to the right and reduced the maximal response to a lesser extent in thyroxine-treated rats than in control rats. Thus we concluded that the total number of cardiac alpha1-adrenoceptors is reduced in thyroxine-treated rats. The change is subtype selective, with alpha1A- and alpha1B-adrenoceptors being reduced in number and alpha1D-adrenoceptor being increased.

Divergent human papillomavirus type 16 variants are serologically cross-reactive

It is not known whether DNA sequence variants of human papillomavirus type 16 (HPV-16) are distinct serotypes. To examine this question, the reactivities of women's sera from Zaire (n = 97) and Denmark (n = 123) were compared in IgG-specific ELISAs based on virus-like particles (VLPs) composed of the L1 major capsid protein derived from an HPV-16 variant common in central Africa (Z-1194) or one common in northern Europe (114K). These L1s differ in seven amino acids. There was a strong correlation between reactivity in the two assays for both sets of sera (correlation coefficients, 0.73 and 0.85 for Zairian and Danish sera, respectively). In only 1 serum was there evidence for a specific reaction to one but not the other VLP variant. The results support the conclusion that the virions of strains Z-1194 and 114K are serologically cross-reactive.

[An experimental study on the effect of operation at one side of the temporomandibular joint on the opposite side]

Condylectomy and menisectomy were performed in left TMJ of 14 rabbits, of them, 7 were treated with periosteal interposition and 7 without. Sixteen weeks after operation, condylar cartilage of the right side were studied and compared with 7 normal rabbits by means of histology and histochemistry. The results show that an operation of high condylectomy and menisectomy with or without interposition on one side of TMJ will result in degenerative changes in the other side (non-operated side). The degenerative changes in the rabbits without any interposition are more serious than those with periosteal interposition.

Strategy for dose escalation using 3-dimensional conformal radiation therapy for lung cancer

PURPOSE

Local failure is a major obstacle to the cure of locally advanced non-small-cell lung cancer. 3-Dimensional conformal radiation therapy (3-DCRT) selects optimal treatment parameters to increase dose to tumor and reduce normal tissue dose, potentially permitting dose escalation. There are several ongoing trials of dose escalation using 3-Dimensional conformal radiation therapy for non-small-cell lung cancer. We performed this analysis to determine if data derived from dose volume histograms could be used as the basis for designing the method of dose escalation in these trials.

METHODS AND MATERIALS

Between 1990 and 1993, 31 patients were treated with 3-DCRT and had complete normal tissue dose volume histograms created as part of the planning process. The stage distribution was stage I/II 13%, stage IIIa in 45%, and stage IIIb in 42%. The median radiation dose to gross disease was 70.2 Gy (52.2-72 Gy). Elective mediastinal irradiation (50.4 Gy) was administered to 52% (16/31) of patients.

RESULTS

The major toxicity encountered in this experience was pulmonary. Dose-volume-histogram data were used to analyze the predictors of toxicity and showed a correlation between risk of pulmonary toxicity and indices of dose to lung parenchyma. Grade 3 or higher pulmonary toxicity occurred in 38% (3/8) of pts with >30%of lung volume receiving > or =25 Gy, versus 4% (1/23) of pts. with < or = 30% lung receiving > or = 25 Gy (p=0.04). Grade 3 or higher pulmonary toxicity occurred in 29% (4/14) of patients with a predicted pulmonary normal tissue complication probability of 12% or higher versus 0% (0/17) in patients with a predicted probability of less than 12% (p=0.03). The single fatality occurred in a patient with a calculated pneumonitis probability of 85% and a high percent (49%) lung volume receiving >= 25 GY.

CONCLUSION

This preliminary experience demonstrates a correlation between lung dose-volume-histogram data and the risk of severe pulmonary toxicity. This provides an opportunity to modify the method of radiation dose escalation. Dose-volume-histogram data can allow escalation according to the risk to the lung parenchyma (which is the major organ of concern) rather than escalation according to tumor dose levels. Because of teh major inter-patient variability of intrathoracic tumor bulk and anatomic distribution, this strategy is intuitively appropriate. This approach may facilitate completion of dose escalation studies and identification of maximum tolerable pulmonary dose levels.

Specific inhibition of the contraction of the rat aorta by estradiol 17 beta

Short-term exposure to estradiol 17 beta is known to inhibit the contraction of vascular smooth muscle preparations that is thought to be mediated by a [Ca++]-dependent mechanism. The purpose of this investigation was to examine the effect of prolonged exposure of vascular preparations to estradiol 17 beta to provide significant time for protein synthesis. We find that treatment of rat aortic rings with estradiol 17 beta (0.37-37 microM) for 15 to 180 min and subsequent removal of the estrogen by washing, attenuated the vasoconstrictor responses to phenylephrine and potassium chloride in a time-dependent manner. The maximum inhibitory effect took 120 min to develop. The inhibitory effect was endothelium independent and not blocked by the cyclooxygenase inhibitor, indomethacin, or by the endothelium derived relaxing factor inhibitor, Nw-nitro-L-arginine methyl ester. This effect was highly stereo-specific in that the 17 alpha isomer was significantly less potent than the 17 beta isomer of estradiol. Further, compared to other steroids, estradiol 17 beta was the most potent. The inhibitory effect of estradiol was blocked completely by pretreatment with the protein synthesis inhibitors, cycloheximide and puromycin, but not by actinomycin D. Electron microscopy showed an increase in ribosomal expression at the rough endoplasmic reticulum after incubation of the rat aorta with estradiol for 120 min. This indicates increased protein synthesis after exposure to estradiol 17 beta. We speculate that the time dependent inhibitory effect of estradiol 17 beta on vascular smooth muscle is related to protein synthesis at the translational level.

beta-Adrenoceptors in endothelium of rabbit coronary artery and alteration in atherosclerosis

The existence of beta-adrenoceptor (beta-AR) in endothelium of rabbit coronary artery and its alteration in atherosclerosis (AS) were determined by relaxation experiments in isolated preparations and in situ hybridization with a digoxigenin-labelled beta 2-AR cDNA probe. The concentration-relaxing response curves for isoproterenol (ISO) and norepinephrine (NE) in the presence of phentolamine were shifted to the right, and the maximal relaxations were reduced by removing the endothelium. Nitric oxide synthase inhibitor L-NG-nitro-arginine reduced the maximal relaxation induced by ISO, while the cyclooxygenase inhibitor indomethacin showed no effect on relaxation. In situ hybridization showed that mRNA for beta-AR was detected not only in smooth muscles, but also in endothelial cells. Coronary artery AS was created by high cholesterol feeding and was confirmed histologically under light microscopy. The relaxation response to acetylcholine (ACh) was abolished or significantly diminished in AS preparations. The relaxation responses to ISO or NE, however, were potentiated in AS arteries, especially in those which showed diminished (but not abolished) ACh response. The relaxation induced by sodium nitroprusside was reduced significantly in the AS arteries. Those results suggest that beta-AR are present in endothelium of rabbit coronary artery, and that endothelium beta-AR-mediated vasorelaxation is potentiated in AS.

Calcitonin gene-related peptide release in endotoxicosis may be mediated by prostaglandins

Three cyclo-oxygenase inhibitors (ibuprofen, indomethacin, and high dose aspirin) and two inhibitors of thromboxane biosynthesis (imidazole and low dose aspirin) were used to evaluate the role of prostaglandins and thromboxane in the release of calcitonin gene-related peptide (CGRP) during endotoxicosis. Endotoxin (lipopolysaccharide B from Salmonella Enteritidis, 5 mg/kg, intravenously) was administered to rats lightly anesthetized with ether during injection. After 3 h, endotoxin significantly elevated plasma CGRP levels by 3-fold. Ibuprofen (50 mg/kg, subcutaneously), indomethacin (10 mg/kg, subcutaneously) and high dose aspirin (100 mg/kg, intraperitoneally (i.p.)), but not imidazole (30 mg/kg, i.p.) or low dose aspirin (15 mg/kg, i.p.), significantly blocked endotoxin-induced CGRP elevations, suggesting that a prostaglandin, but not thromboxane, served as a mediator of CGRP release during endotoxicosis. Because endotoxin-induced production of prostaglandins is greatly diminished in endotoxin-tolerant rats (following multiple exposures to low dose endotoxin), we tested whether endotoxin-induced CGRP release also becomes diminished in tolerant rats. Accumulation of plasma CGRP was greatly diminished in endotoxin-tolerant rats exposed to endotoxin (5 mg/kg, intravenously), consistent with a mediator role for prostaglandins in the CGRP release during endotoxicosis.

Inhibition of oncogene expression by green tea and (-)-epigallocatechin gallate in mice

The effects of tea drinking on the tobacco-specific nitrosamine 4-(methylnitrosamine)-1-(3-pyridyl)-1-butanone (NNK)-induced mouse lung oncogene expression and the effect of topical application of the tea polyphenol component (-)-epigallocatechin-3-gallate (EGCG) on 12-O-tedradecanoylphorbol-13-acetate (TPA)-induced mouse skin oncogene expression were investigated. In the first experiment, mice were treated with NNK (1.3 mg/kg body wt ip) once a day for three days and were given 2% tea in drinking water during the whole experimental period. After four or eight weeks, the lung tissue of the mice treated with NNK displayed a significantly high level of expression in c-myc, c-raf, and c-H-ras oncogenes, and they were all inhibited by tea drinking with inhibitory rates of 50%, 20%, and 50%, respectively. In the second experiment, a single application of 10 nmol of TPA to mouse skin led to a marked increase in the transcripts' level of ornithine decarboxylase (ODC) gene, protein kinase C (PKC) gene, and c-myc oncogene at four hours after TPA administration. Topical application of EGCG (1 or 5 mumol) one hour before the application of TPA inhibited all TPA-induced gene expression in a dose-dependent fashion. These results confirm the anticarcinogenic effects of tea and suggest that a possible mechanism is the effect of tea on carcinogen-induced oncogene expression.

Correlation of the response to nitroglycerin in rabbit aorta with the activity of the mu class glutathione S-transferase

The relationship between the activity of glutathione S-transferases (GSTs), especially the mu isozyme, and the production of responses to nitroglycerin (GTN) was investigated in rabbit aorta. GST mu isozyme activity was measured using trans-stilbene oxide (TSO) as a substrate. Each aorta was divided into four parts, two of which were frozen for enzymatic analyses while the remaining two were used to measure the effects of GTN (0.5 microM), i.e. the increase in cGMP levels and the corresponding relaxation. Thus, all three measures were obtained in each individual rabbit aorta. Eight different rabbits were studied. An excellent correlation was obtained between the rise in cGMP and the mu isozyme activity (r2 = 0.948). A good correlation was also obtained between TSO activity and the relaxation response to GTN. Total GST activity did not correlate well with either cGMP increases or percent relaxation. These observations indicate that the activity of the mu isozyme measured using TSO and not the total GST correlates with the responses to GTN in the in vitro rabbit aorta model.

Selectivity of agonists for cloned alpha 1-adrenergic receptor subtypes

The potencies and intrinsic activities of agonists in activating cloned alpha 1-adrenergic receptor (AR) subtypes were compared. The hamster alpha 1B-, bovine alpha 1C-, or rat alpha 1A/D-ARs were expressed at high levels in human embryonic kidney 293 cells. Catecholamines and phenylethylamines, but not lower efficacy agonists, were more potent in inhibiting radioligand binding to the expressed alpha 1A/D subtype than to the alpha 1B or alpha 1C subtypes; this selectivity remained in the presence of different buffers, nucleotides, and cations. Activation of all three subtypes caused substantial increases in [3H]inositol phosphate formation in cells grown in 96-well plates. Pretreatment with phenoxybenzamine decreased maximal responses to norepinephrine (NE) with only small decreases in apparent potency, suggesting similar small receptor reserves for all three subtypes. The catecholamines NE, epinephrine, and 6-fluoro-NE were full agonists with similar potencies at the three subtypes; alpha-methyl-NE was also a full agonist but was about 20-fold less potent at alpha 1B-ARs than at alpha 1C- or alpha 1A/D-ARs. Phenylephrine had similar potencies at all three subtypes but gave a submaximal response at alpha 1B-ARs. Methoxamine was a full agonist at alpha 1C- and alpha 1A/D-ARs, with about 20-fold greater potency at the alpha 1C subtype, but showed lower intrinsic activity at alpha 1B-ARs. A number of imidazolines, amidephrine, and SKF 89748 had substantial intrinsic activity at alpha 1C-ARs but little or no intrinsic activity at the other two subtypes. We conclude that the potencies of many agonists in competing for radioligand binding sites are related to their potencies in activating functional responses but that this relationship is not the same for all subtypes. NE and epinephrine activate all three cloned alpha 1-AR subtypes with similar potencies and intrinsic activities, but many widely used agonists show significant selectivity for different alpha 1-AR subtypes.

Role of alpha 1A- and alpha 1B-adrenoceptors in phenylephrine-induced positive inotropic response in isolated rat left atrium

We determined the distribution of alpha 1A- and alpha 1B-adrenoceptor subtypes and their functional roles in phenylephrine (PE)-induced positive inotropic responses in rat atrium. Radioligand binding assays in membrane preparations of rat atria showed that 62% of [125I]BE 2254 binding sites were irreversibly inactivated by pretreatment with 20 microM chloroethylclonidine (CEC). Inhibition curves for WB 4101 and 5-methyl-urapidil (5-MU) were better fit by a two-site model, comprising 29-35% high-affinity sites and 65-71% low-affinity sites, suggesting that rat atria contains both alpha 1A and alpha 1B subtypes in a ratio of approximately 1:2. In isolated perfused atria, pretreatment with CEC inhibited the maximum PE-induced positive inotropic response by 55%, and pA2 values for WB 4101 and 5-MU in inhibiting this response were 8.26 +/- 0.4 and 7.85 +/- 0.07, respectively, between the KD values for alpha 1A and alpha 1B subtypes. PE shifted the concentration-contractile response curve for Ca2+ to the left and upward. Pretreatment with CEC completely abolished whereas 1 nM WB 4101 did not alter, the effect of PE on Ca2+ sensitivity. These results demonstrate that both alpha 1A- and alpha 1B- adrenoceptor subtypes are involved in the PE-induced positive inotropic response. Only activation of the alpha 1B subtype potentiates the positive inotropic effect induced by increasing extracellular Ca2+, however, which suggests that the mechanisms involved in the action of the two subtypes may differ at least in part.

[A study on alcohol drinking pattern in freshmen and sophomores]

Alcohol drinking pattern in 871 freshmen and sophomores of Han nationality was studied. Results showed 92.7% of the male and 72.9% of the female students were alcohol drinkers. There were highly significant differences in alcohol drinking pattern and types of alcoholic beverage they drank between males and females (P < 0.0001), and between students specializing in different subjects (P < 0.01). Alcohol drinking pattern of male students was influenced by their academic concerns and the drinking behavior of their fathers and friends.

Role of K+ channels in neuropeptide Y-induced vasoconstriction in rabbit cerebral basilar artery

The role of K+ channels in the direct vasoconstrictive response induced by neuropeptide Y was investigated in isolated basilar arteries of rabbits and in vivo in rats. K+ channel openers, either BRL38227 or diazoxide, caused dose-dependent and complete relaxation of isolated arteries precontracted by neuropeptide Y. Exposure to both BRL38227 and diazoxide shifted the concentration-response curves for neuropeptide Y to the right without changing the maximal response. However, BRL38227 antagonized the angiotensin II-induced vasoconstriction noncompetitively. In vivo, the pressor responses produced by neuropeptide Y were significantly inhibited by pretreatment with BRL38227 in anesthetized rats. These results show that K+ channel openers antagonize neuropeptide Y-induced vasoconstriction in a competitive manner and suggest that blockade of K+ channels contributes, at least in part, to the direct vasoconstrictive effect of neuropeptide Y.

The inhibitory effect of Chinese tea and its polyphenols on in vitro and in vivo N-nitrosation

The objective of this study is to evaluate the possible role of Chinese tea as a natural inhibitor of N-nitrosation, and to compare the relative inhibitory potency of various kinds of Chinese tea in vitro and in vivo. Studies on the inhibitory effect of 145 samples of Chinese tea on the formation of N-nitrosomorpholine (NMOR) showed that the inhibitory potency of the 7 types of Chinese tea differed greatly, the average blocking rate of green tea (89.04%, n = 60), crush, tear, and curl (CTC) black tea (86.99%, n = 13), brick tea (85.40%, n = 7), jasmine tea (84.99%, n = 21), Oolong tea (82.37%, n = 9), sun-dried tea (61.99%, n = 13) and Chinese Gongfu black tea (54.98%, n = 22), were positively correlated with their polyphenols contents. The inhibitory effect of green tea and black tea on endogenous N-nitrosation was also confirmed in 3 human volunteer experiments. Drinking tea after meal had a greater effect than drinking it before meal. It is concluded that Chinese tea can exert a relatively strong inhibitory potency for N-Nitroso compounds (NOC) formation both in vitro and in humans, and the active constituents may be related to their polyphenols contents, especially the tea catechin derivatives. The results also demonstrated that the amounts of NMOR formed in vitro depended on the molecular structure of tea catechin derivatives and their molar ratios to nitrite.

Comparison of alpha 1-adrenergic receptor subtypes and signal transduction in SK-N-MC and NB41A3 neuronal cell lines

We compared the alpha 1-adrenergic receptor subtypes in two neuronal cell lines, SK-N-MC (human neuroepithelioma) and NB41A3 (murine neuroblastoma). 125I-BE 2254 labeled alpha 1-adrenergic receptor binding sites in membranes from both cell lines. Pretreatment with the alpha 1B-selective alkylating agent chloroethylclonidine (CEC) completely eliminated these binding sites in NB41A3 cells but caused only a 50% loss in SK-N-MC cells. Displacement with subtype-selective antagonists suggested that NB41A3 cells express only the alpha 1B subtype, whereas SK-N-MC cells express a pharmacologically heterogeneous receptor population, including both alpha 1A and alpha 1B subtypes. Norepinephrine increased [3H] inositol phosphate formation in both cell lines, but with different sensitivities to pertussis toxin and the presence of extracellular Ca2+. CEC pretreatment eliminated this response in NB41A3 cells but caused a maximal 42% reduction in SK-N-MC cells. Use of subtype-selective antagonists showed that the [3H]inositol phosphate response involved only the alpha 1B subtype in NB41A3 cells but a combination of subtypes in SK-N-MC cells. Norepinephrine induced both transient and sustained increases in intracellular Ca2+ concentrations in both cell lines, as measured with fura-2. CEC pretreatment abolished the Ca2+ response in NB41A3 cells but had little effect in SK-N-MC cells. In SK-N-MC cells the Ca2+ response was potently blocked by alpha 1A-selective antagonists. Chelation of extracellular Ca2+ eliminated the sustained component of the Ca2+ signal in both cell lines. Poly(A)+ RNA from NB41A3, DDT1MF-2, BC3H1, and MDCK-D1 cell lines showed one or more prominent transcripts (2.2-4.2 kilobases) that strongly hybridized to the hamster alpha 1B cDNA probe but not to the bovine alpha 1C or rat alpha 1D cDNA probes. Poly(A)+ RNA from SK-N-MC cells showed multiple transcripts (1.3-5.6 kilobases) that hybridized to both hamster alpha 1B and rat alpha 1D but not bovine alpha 1C cDNA probes. We conclude that NB41A3 cells contain exclusively alpha 1B-adrenergic receptors linked to inositol phosphate formation and mobilization of intracellular Ca2+, whereas at least two alpha 1-adrenergic receptor forms, which resemble the alpha 1A and alpha 1B subtypes, coexist in SK-N-MC cells. The CEC-insensitive alpha 1A-like subtype in SK-N-MC cells is capable of increasing inositol phosphate formation and mobilizing intracellular Ca2+.

Coexisting beta 1- and atypical beta-adrenergic receptors cause redundant increases in cyclic AMP in human neuroblastoma cells

In SK-N-MC human neuroblastoma cells, the cAMP response to 10 nM isoproterenol (ISO) is mediated primarily by beta 1-adrenergic receptors. However, responses to higher concentrations of ISO (100-1000 nM) were only weakly blocked by beta 1- and beta 2-selective antagonists. When beta 1 receptors were blocked with 10 microM CGP 20712A, catecholamines still maximally activated cAMP accumulation, with only small decreases in potency. In the presence of CGP 20712A, beta blockers inhibited the response to ISO stereoselectively but with relatively low potencies. Pindolol derivatives were partial agonists with low potencies, and the atypical agonist BRL 37344 was a partial agonist with an intermediate potency. All binding sites in these cells labeled by 125I-cyanopindolol were of the beta 1 subtype. Nuclease protection assays indicated that SK-N-MC cells contain mRNA for both the human beta 1- and beta 3-adrenergic receptors, with the beta 3 subtype mRNA being expressed 25-50% more abundantly than that for the beta 1 subtype. Northern blot hybridizations showed the presence of two beta 3 mRNA transcripts of 3.1 and 2.4 kilobases. These results suggest that beta 1- and atypical beta-adrenergic receptors coexist in these cells and cause redundant increases in cAMP formation. Although molecular approaches suggest that the atypical subtype is the beta 3, the observed drug specificity differs from that reported for the expressed recombinant human beta 3 receptor.

Improved gas chromatographic assay for the simultaneous determination of nitroglycerin and its mono- and dinitrate metabolites

A sensitive, specific capillary gas chromatographic-electron-capture detection method for the simultaneous determination of nitroglycerin (GTN), 1,2- and 1,3-glyceryl dinitrate (1,2-GDN and 1,3-GDN, respectively) and 1- and 2-glyceryl mononitrate (1-GMN and 2-GMN, respectively) is reported. The minimum quantifiable concentration for GTN, GDNs and GMNs is 0.4 ng/ml in plasma, with extraction recoveries for GMNs greater than 76% and for GTN and the GDNs greater than 95%. Over the full range of quantifiable concentrations the inter-run assay precision and accuracy were less than 13 and 11%, respectively, for all five nitrates. Similar intra-run assay precision and accuracy values were found. The method was employed in the preliminary in vitro examination of GTN, GDN and GMN kinetics in human blood. Following addition of GTN to human blood, the ratio of 1,2-GDN to 1.3-GDN maximum concentrations (Cmax) was ca. 7:1, reflecting preferential denitration of the GTN molecule at the primary positions, while the Cmax ratio for 2-GMN to 1-GMN in this system was ca. 6:1, representing a highly selective if not specific primary denitration of the 1,2-GDN molecule. Following the intravenous administration of 1,2-GDN to five healthy male volunteers, 2-GMN/1-GMN Cmax ratios averaged 8.8:1, representing a highly selective but not specific formation of 2-GMN from the 1,2-GDN molecule. The assay will find utility in in vitro studies attempting to address the molecular pharmacology of GTN and its metabolites, and in in vivo clinical pharmacology studies attempting to address the relationship between pharmacokinetics and pharmacodynamics of GTN and its metabolites.

Inhibition of tobacco-specific nitrosamine-induced lung tumorigenesis in A/J mice by green tea and its major polyphenol as antioxidants

In this study we examined the effects of green tea and its major components, (-)-epigallocatechin gallate (EGCG) and caffeine, on the tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in A/J mice. We also studied the effects of green tea and EGCG on O6-methylguanine and 8-hydroxydeoxyguanosine (8-OH-dGuo) formation in lung tissues caused by NNK treatment. Mice were given 2% tea, 560 ppm EGCG, or 1120 ppm caffeine in drinking water for 13 weeks. During this time, NNK (11.65 mg/kg body weight) was administered by gavage three times weekly for 10 weeks from weeks 3 to 12. The bioassay was terminated 6 weeks after the last NNK treatment. Mice treated with NNK developed 22.5 lung adenomas per mouse, whereas NNK-treated mice that drank green tea or EGCG as drinking water developed only 12.2 (P less than 0.01) and 16.1 (P less than 0.05) tumors per mouse, respectively. Mice that drank green tea or caffeine solution showed lower body weight gains, although little difference in water and diet consumption was noted in these groups. While green tea and EGCG exerted little effect on the formation of O6-methylguanine, a critical DNA lesion in NNK lung tumorigenesis, both treatments suppressed the increase of 8-OH-dGuo levels in mouse lung DNA. The inhibition of 8-OH-dGuo formation in lung DNA by green tea and EGCG is consistent with their ability to inhibit lung tumorigenesis by NNK. Because 8-OH-dGuo is a DNA lesion caused by oxidative damage, these results suggest that the mechanism of inhibition by green tea and EGCG in NNK-induced lung tumorigenesis is due at least partly to their antioxidant properties.

Subtypes of α1-adrenoceptors in DDT1 MF-2 and BC3H-1 clonal cell lines

We examined which subtype(s) of alpha 1-adrenoceptors are expressed in the widely used DDT1 MF-2 and BC3H-1 cell lines. Pretreatment with chloroethylclonidine (CEC) inactivated 76-85% of the specific [125I]BE 2254 binding sites in membrane preparations from both cell lines. Competition with subtype-selective competitive antagonists showed primarily the alpha 1B subtype in both cell lines. However, in BC3H-1 cells 5-methyl-urapidil showed complex behavior suggesting that about half of the binding sites had a lower affinity. Chloroethylclonidine pretreatment eliminated [3H]inositol phosphate responses to norepinephrine in both cell lines. Measurement of intracellular Ca2+ with fura-2 in DDT1 MF-2 cells showed that norepinephrine induced a complex response involving both transient and sustained components. Chloroethylclonidine pretreatment blocked both responses, while chelation of extracellular Ca2+ left the transient response intact but eliminated the sustained component. These results support previous work that these cell lines contain alpha 1B-adrenoceptors linked to inositol phosphate formation and mobilization of intracellular Ca2+. However, these results show that alpha 1B-adrenoceptors can be linked to Ca2+ influx as well as intracellular mobilization, and support the existence of pharmacologically distinct alpha 1B variants.

Inhibition by germanium oxide of the mutagenicity of cadmium chloride in various genotoxicity assays

The effects of germanium oxide on the genotoxicity of cadmium chloride were investigated. The incorporation of [3H]thymidine into testicular DNA was inhibited in mice injected ip with 1.35, 1.80 or 2.70 mg cadmium chloride/kg body weight. Germanium oxide (0.05 or 0.1 mg/kg body weight, sc) alone did not affect [3H]thymidine incorporation into testicular DNA but 0.05 mg germanium oxide/kg antagonized the inhibitory effect of 1.35 mg cadmium chloride/kg. However, combinations of the other doses of the two compounds did not show statistically significant antagonistic effects. Cadmium chloride significantly increased the frequencies of micronucleus formation in polychromatic erythrocytes, and of chromosome aberrations in the bone marrow of mice treated with 0.7, 1.4 or 2.7 mg/kg body weight, in a dose-related manner. These effects were inhibited by germanium oxide at doses of 0.1 or 0.5 mg/kg body weight, although germanium oxide alone did not affect micronucleus formation or the chromosome aberration rate. Cadmium chloride produced a dose-related increase in the frequency of sister chromatid exchanges in cultured human lymphocytes at concentrations of 5, 10 or 50 mumol. This effect was also inhibited by germanium oxide (0.05 or 0.1 mumol), although germanium oxide alone had no effect. There was a dose-related increase in the frequency of sperms with abnormal head morphologies from mice treated with 0.6, 1.1 or 2.2 mg cadmium chloride/kg body weight and this too was antagonized by the injection of germanium oxide (0.1 or 0.5 mg/kg body weight). Germanium oxide alone did not affect the frequency of sperm-head abnormalities.

Lack of effects of selenium on N-nitrosomethylbenzylamine-induced tumorigenesis, DNA methylation, and oncogene expression in rats and mice

The effects of dietary selenium deficiency and excess on N-nitrosomethylbenzylamine-(NMBA) induced esophageal neoplasia in rats and forestomach tumors in mice and the effects of dietary selenium on DNA adduct formation and on the activities of DNA adduct-repairing enzyme and oncogene expression in rat esophagus were investigated. The esophageal and forestomach tumors were induced by administration of NMBA by gavage with a total dose of 39 mg/kg body wt in rats and 12 mg/kg body wt in mice. Neither selenium dietary deficiency (Se < 0.02 ppm) nor selenium excess (2.0 ppm) showed any significant effect on the incidence of tumors or number of tumors per tumor-bearing animal. For the DNA adduct formation studies, rats were given a dose of NMBA intraperitoneally after six weeks on the different selenium-containing diets. No significant difference in the amount of the DNA adduct O6-methyldeoxyguanosine was found among the different selenium-treated groups. In a parallel group of rats that did not receive NMBA, the levels of esophageal O6-methyldeoxyguanosine DNA methyltransferase were not significantly altered by dietary selenium levels. The c-myc oncogene expression in rat esophagus was induced by the administration of NMBA (3 mg/kg body wt) by gavage once a week for eight weeks. Dietary selenium did not show any effects on its expression. On the basis of the results of these studies, dietary selenium has no effects in the NMBA-induced tumor model.

Calcitonin gene-related peptide (CGRP) causes endothelium-dependent cyclic AMP, cyclic GMP and vasorelaxant responses in rat abdominal aorta

Calcitonin gene-related peptide (CGRP), a neuropeptide found in nerves surrounding most blood vessels, is a potent hypotensive agent in both humans and rats. In isolated strips of rat thoracic aorta, CGRP has been reported to cause endothelium-dependent relaxation. To study the cellular and molecular mechanisms involved in CGRP-induced vasodilation, we investigated the roles of two second messengers, cyclic AMP and cyclic GMP, as potential mediators of the signal transduction mechanism leading to vasodilation in response to CGRP in rat aorta. In the present study, the abdominal aorta, rather than thoracic aorta, was used because of its higher content of endogenous CGRP and, therefore, the greater likelihood of regulation by CGRP in vivo. Each abdominal aortic ring was precontracted with norepinephrine (NE) at its EC50 concentration (10-20 nM). CGRP (3-300 nM) caused concentration-dependent relaxations (reducing the NE-induced contractions by 34%) that were completely dependent on endothelium. The relaxations in response to CGRP were correlated in a time- and concentration-dependent manner with increases in aortic levels of both cyclic AMP and cyclic GMP. CGRP (100 nM) caused significant elevations of cyclic AMP levels (1.4 to 3.2 pmol/mg protein, at 1 min) and cyclic GMP levels (1.6 to 3.6 pmol/mg protein, at 30 s). Like the vasorelaxant responses, both cyclic AMP and cyclic GMP responses to CGRP were totally dependent on the endothelium. Pre-incubation with indomethacin (3 microM, 15 min) did not alter cyclic AMP responses to CGRP (100 nM), suggesting that prostaglandins are not involved. Therefore, CGRP-induced vasodilations of abdominal aorta involve an endothelium-dependent mechanism associated with cyclic GMP elevations, similar to the mechanisms of vasodilation in response to acetylcholine and other endothelium-dependent vasodilators. However, CGRP-induced relaxations of aorta involve an additional mechanism (i.e., endothelium-dependent cyclic AMP elevations), which may also contribute to the intracellular mechanism of aortic vasodilation in response to CGRP.

Calcitonin gene-related peptide (CGRP)-induced cyclic AMP, cyclic GMP and vasorelaxant responses in rat thoracic aorta are antagonized by blockers of endothelium-derived relaxant factor (EDRF)

The mechanism of CGRP-induced vasodilation in rat thoracic aorta was investigated using antagonists of the classical endothelium-derived vasorelaxant factor (EDRF) and comparisons with acetylcholine-induced vasodilations. The CGRP-induced relaxations of isolated rings of rat thoracic aorta were completely dependent on the presence of endothelium and were associated with increases in the levels of both cyclic AMP and cyclic GMP, the same as in our previous study using rat abdominal aorta. Maximum relaxations to CGRP, which represented 40-50% reversal of the norepinephrine-induced contractions, occurred with 100 nM CGRP. Addition of acetylcholine (ACh, 1 microM) to aortic rings, which were already maximally relaxed to CGRP, caused further relaxation to 100%, suggesting that CGRP may use a mechanism (or pool of EDRF) different from that of ACh. Both CGRP- and ACh-induced relaxations of aorta were significantly inhibited by the EDRF blocking agents, hemoglobin (10 microM), methylene blue (10 microM), and nordihydroguaiaretic acid (NDGA, 10 microM). In fact, hemoglobin and NDGA were more effective as inhibitors of CGRP-induced relaxations than ACh-induced relaxations. Hemoglobin, methylene blue and NDGA also inhibited the CGRP-induced increases in both cyclic AMP and cyclic GMP levels. On the other hand, indomethacin, a cyclo-oxygenase inhibitor, did not alter CGRP-induced vasorelaxations or increases in either cyclic AMP or cyclic GMP levels, suggesting that prostaglandins are not involved. Therefore, CGRP-induced vasodilations in rat thoracic aorta appear to involve EDRF, leading to cyclic GMP elevations in smooth muscle and ultimately vasorelaxations. However, another previously undescribed mechanism, which involves EDRF-dependent and indomethacin-resistant elevations of cyclic AMP levels, is triggered by CGRP in thoracic aorta. This novel EDRF-dependent cyclic AMP response may contribute to the CGRP-induced vasodilation in rat thoracic aorta.

[Prevention of in vivo formation of NMBz A and the formation of oesophageal tumour by tea in rats]

Five groups of rats (22 per group) were intubated with precursors of N-Nitrosomethylbenzylamine (NMBzA), i.e. methylbenzylamine (1 mmol/kg) and sodium nitrite (0.5 mmol/kg), and five varieties of Chinese tea. One positive control group was intubated with precursors of NM2A without tea and one negative control group with tap water and sodium nitrite. After 12 week's treatment, significantly less lesions and papillomas in esophageal mucosa, examined by naked eye or by microscope, were found in the tea-treated groups than in the non-tea-treated positive control group. The results confirmed the anti-tumour ability of Chinese tea by blocking the in vivo formation of NMBzA in rats.

[Preliminary studies on the inclusion compound of cholate with beta-cyclodextrin]

beta-Cyclodextrin inclusion compound has been proved able to eliminate the bitter taste of cholate and bile. A right amount of beta-cyclodextrin put in aqueous solution of cholate and bile will remove the bitter taste completely, beta-Cyclodextrin doesn't affect the identification or content determination of cholic acid.

Subtypes of alpha 1-adrenoceptors in rat blood vessels

Two alpha 1-adrenoceptor subtypes (alpha 1A and alpha 1B) have been distinguished by competitive antagonists and the alkylating agent chloroethylclonidine. The chloroethylclonidine-insensitive subtype (alpha 1A) has been suggested to selectively activate Ca2+ influx through dihydropyridine-sensitive channels in smooth muscle. We compared the effects of chloroethylclonidine and nifedipine on contractile responses to norepinephrine (NE) in rat blood vessels. Pretreatment with chloroethylclonidine caused a large shift to the right and decrease in maximum for NE-induced contractions of rat aorta, however, nifedipine had no effect in this tissue. Chloroethylclonidine had no effect on NE-induced contractions of rat renal arteries, which were almost completely abolished by nifedipine. Both chloroethylclonidine and nifedipine partially attenuated NE-induced contractions in rat mesenteric artery and portal vein. Addition of nifedipine abolished residual contractions remaining after chloroethylclonidine pretreatment in all four types of vessels. The pA2 for the competitive antagonist WB 4101 was highest in renal artery and lowest in aorta. These results suggest that the sensitivity of rat blood vessels to chloroethylclonidine is inversely related to their sensitivity to nifedipine, and support the existence of two alpha 1-adrenoceptor subtypes in rat blood vessels. Rat aorta appears to contain primarily alpha 1B receptors, renal artery primarily alpha 1A, and mesenteric artery and portal vein mixtures alpha 1A of and alpha 1B.

[Analysis of 38 cases with epilepsy in forensic psychiatric evaluation]

Analysing 38 cases with epilepsy in forensic psychiatric evaluation shown that violence behavior were frequently seen, especially significant difference in psychomotor epilepsy in comparison with the other typical epilepsy (0. 01), and that epileptic psychopathy were frequently seen in intermission. Authors dealt with criminal responsibility in epileptic psychopathy.

Direct observations of ligand dynamics in hemoglobin by subpicosecond infrared spectroscopy

The photodissociation of CO from HbCO at ambient temperature is studied by means of a femtosecond IR technique. The bleaching of the FeCO absorption and the appearance of a new IR absorption near that of free CO are both observed at 300 fs after optical excitation. The bleach does not recover on the time scale of a few picoseconds but does recover by approximately 4% within 1 ns, which suggests that a barrier to recombination is formed within a few picoseconds. The CO spectrum does not change significantly between 300 fs and 1 ns, suggesting that the CO quickly finds some locations in the heme pocket that are not more than a few angstroms from the iron. The de-ligated CO appears in its ground vibrational level. There is evidence that 85 +/- 10% of this CO remains in the heme pocket at 1 ns; it probably resides there for 50 ns. The flow of excess vibrational energy from the heme to the solvent was directly observed in the IR experiments. The heme cools within 1-2 ps while thermal disruption of the surrounding solvent structure requires approximately 30 ps.

Changes in cardiac neuropeptide Y after experimental myocardial infarction in rat

We have investigated the hypothesis that neuropeptide Y (NPY) is released from noradrenergic sympathetic nerves during experimentally induced myocardial infarction. A left thoracotomy was performed, the left main coronary artery ligated, and the animals sacrificed 4 or 48 h later. NPY levels in heart tissue from these rats and sham-operated controls were measured with radioimmunoassay. Levels of NPY in the right atrium were greater than other regions of the rat heart. After ligation of the left coronary artery, the concentration of NPY in the infarcted area of the left ventricle was reduced at 4 and 48 h when compared to a similar area in sham-operated rats. NPY levels in the septum were unchanged. The results suggest that during myocardial infarction, NPY is released from nerves in the infarcted region and may deleteriously affect increased collateral blood flow surrounding the infarcted tissue.

[The effect of Chinese teas on the occurrence of oesophageal tumor caused by N-nitrosomethylbenzylamine in rats]

Five groups of rats were given different varieties of Chinese tea as drinking water and on additional two groups of rats were given water with or without N-nitrosomethylbenzylamine (NMBzA) as controls. Except the control group, all the animals were intubated with NMBzA (5 mg.kg-1/wk) for 6 or 12 weeks. After 6 weeks, the incidence of oesophageal mucosa lesions was significantly lower in the tea-treated rats (16-59%) than the control group with NMBzA (100%). After 12 weeks, the incidence of oesophageal tumor was also significantly lower in the tea-treated groups (42-67%) than the control group with NMBzA (90%). Similar results were obtained in the tumor size and the number of tumors developed. The anti-carcinogenic effects of the 5 varieties of Chinese tea were also not the same the Fujian Oolong tea and Jasmine tea had the strongest effect. The results suggest that Chinese tea can inhibit the carcinogenesis caused by N-nitroso compound.

Effects of neuropeptide Y on contraction, relaxation, and membrane potential of rabbit cerebral arteries

The effects of porcine neuropeptide Y (NPY) on agonist-induced contraction, relaxation, and intracellular membrane potential were studied in isolated ring segments of rabbit cerebral arteries. NPY caused contraction of cerebral arteries with a mean EC50 of 2.7 +/- 0.07 nM. After exposure of cerebral arteries to 1.5 nM NPY, the potencies of norepinephrine (NE) and histamine in causing contraction were increased by approximately twofold, with no change in maximal contraction. In cerebral arteries contracted with histamine, adenosine, and acetylcholine-induced relaxation was inhibited by 7-14-fold in the presence of 1.5 nM NPY, with no change in maximal relaxation. These effects of NPY were not altered by sympathetic denervation of cerebral arteries. Intracellular membrane potential in smooth muscle cells of cerebral arteries was measured using glass microelectrodes and averaged -66 +/- 1 mV. NPY 3 nM, ouabain 3 microM, and K+ Krebs solution 1 mM depolarized cerebral arteries by 15, 22, and 14 mV, respectively. In arteries depolarized by ouabain or 1 mM K+ Krebs solution, 3 nM NPY caused no additional depolarization. The potency of NE in causing contraction of cerebral arteries was increased by 3 microM ouabain (3.8-fold) and 1 mM K+ Krebs solution (1.9-fold); however, 3 nM NPY in the presence of ouabain or 1 mM K+ Krebs solution caused no greater increase in agonist potency. Ouabain 3 microM inhibited adenosine-induced relaxation by 5.1-fold whereas addition of 3 nM NPY to ouabain exposed arteries caused an additional 4.6-fold inhibition of relaxation. Ouabain and ouabain plus NPY also decreased the maximal relaxant effect of adenosine. These results suggest that the ability of NPY to potentiate contraction and inhibit relaxation of cerebral arteries is caused, at least in part, by NPY-induced membrane depolarization.

High levels of NPY in rabbit cerebrospinal fluid and immunohistochemical analysis of possible sources

We have analyzed rabbit cerebrospinal fluid for neuropeptide Y (NPY)-like immunoreactivity, using high performance liquid chromatography (HPLC) and radioimmunoassay (RIA) and examined the anatomical relationship of NPY-containing fibers to the cerebral vasculature and the third cerebral ventricle. Cerebrospinal fluid (CSF) obtained from the cisterna magna of rabbits was injected into a C18 column and subjected to HPLC. The fractions were collected, dried and reconstituted in buffer for NPY radioimmunoassay. A single peak of NPY immunoreactivity was obtained which corresponded in retention time to synthetic porcine NPY. Analysis of CSF samples produced displacement curves parallel to the standard curve. Immunohistochemistry revealed numerous NPY-labeled fibers which penetrated the ependymal lining of the third cerebral ventricle and directly bordered the ventricular lumen. Other fibers were observed in the pia which lines the ventral aspect of the hypothalamus. The basilar artery, its branches and other cerebral vessels were surrounded by NPY-labeled fibers. The results show that: (1) approximately 1 ng/ml of NPY immunoreactivity which corresponds chromatographically to synthetic porcine NPY is present in rabbit CSF; (2) NPY-containing fibers surround the basilar artery and other cerebral vessels; (3) NPY may be released into the CSF from axons in the pia and from axons which penetrate the ependymal lining of the third ventricle. These observations form the basis for our analysis of the vasoconstrictor effects of NPY and its role in cerebrovasospasm after experimental subarachnoid hemorrhage.

Neuropeptide Y: vasoconstrictor effects and possible role in cerebral vasospasm after experimental subarachnoid hemorrhage

The possible role of neuropeptide Y (NPY) as a vasoconstrictor substance contributing to the development of cerebral vasospasm after experimental subarachnoid hemorrhage was studied. Autologous blood was injected into the cisterna magna of control rabbits and rabbits that had received bilateral superior cervical ganglionectomy 2 days before blood injection. Three days after blood injection the concentration of NPY in cerebrospinal fluid (CSF) was 5971 +/- 551 pg/ml while CSF from control animals contained 992 +/- 162 pg/ml of NPY. The effects of porcine NPY on norepinephrine-induced contraction of rabbit cerebral arteries were also studied in vitro. NPY (1.2 nM) caused a 3-fold potentiation of norepinephrine-induced contraction of cerebral arteries. CSF from control rabbits diluted by 50% with Krebs solution had no significant effect on norepinephrine-induced contraction of cerebral arteries when compared to responses in Krebs solution only; however, diluted CSF from denervated blood-injected rabbits potentiated norepinephrine-induced contraction by 2.6-fold. Antiserum containing NPY specific antibodies was used to immunoprecipitate the peptide from CSF taken from denervated blood-injected rabbits. CSF treated with this antiserum contained less than 40 pg/ml of NPY and had no effect on norepinephrine-induced contraction of cerebral arteries. These results show that the concentration of NPY in CSF of rabbits is elevated after experimental subarachnoid hemorrhage. In addition, NPY in CSF can potentiate the vasoconstrictor effect of norepinephrine which may contribute to the development of cerebral vasospasm.

Comparison of alpha 1-adrenergic receptor subtypes distinguished by chlorethylclonidine and WB 4101

We showed previously that subtypes of alpha 1-adrenergic receptors can be differentiated by selective inactivation with chlorethylclonidine (CEC) [Mol. Pharmacol. 32:505-510 (1987)] or by their affinities for the competitive antagonist WB 4101 [Nature (Lond.) 329:333-335 (1987)]. Examining eight rat tissues, the proportions of 125IBE 2254-binding sites sensitive to inactivation by CEC correlated significantly (p less than 0.05) with the proportion having a low affinity for WB 4101. However, the proportion of CEC-sensitive sites was always smaller than the proportion of low affinity WB 4101 sites. Further experiments showed that repetitive pretreatment with CEC or pretreatment under hypotonic conditions caused a larger inactivation of binding sites, suggesting that CEC did not access all sites under the isotonic conditions used previously. The proportions of binding sites inactivated by 10 microM CEC under hypotonic conditions were quantitatively similar to and correlated significantly (p less than 0.01) with the proportion having a low affinity for WB 4101. Pretreatment of hippocampus and vas deferens with CEC caused a loss of all low affinity WB 4101-binding sites, leaving only high affinity sites. In vas deferens, CEC pretreatment decreased the potency of norepinephrine in stimulating 3H-inositol phosphate accumulation but not contractile responses. In rat liver slices, CEC inactivated norepinephrine-stimulated 3H-inositol phosphate accumulation in parallel with 125IBE-binding sites. These results suggest that: 1) the CEC-sensitive and -insensitive 125IBE 2254-binding sites are equivalent to those with a low and high affinity for WB 4101, respectively, and 2) the CEC-sensitive binding sites with a low affinity for WB 4101 are the alpha 1-adrenergic receptors linked to inositol phospholipid hydrolysis.

Heterogeneity of alpha 1-adrenergic receptors revealed by chlorethylclonidine

Chlorethylclonidine (CEC) has previously been shown to inactivate only a subpopulation of the alpha 1-adrenergic receptor binding sites in rat brain. We compared alpha 1-adrenergic receptors in different tissues to determine whether such selective inactivation might reveal the presence of distinct receptor subtypes. Pretreatment of broken cell preparations with 10 microM CEC for 10 min caused a 70-80% decrease in the density of specific 125IBE 2254 binding sites in rat liver and spleen, a 25% decrease in neocortex, but no significant loss in kidney, hippocampus, heart, vas deferens, or caudal artery. The effect of CEC in liver was not reversed by extensive washing, suggesting irreversible inactivation. The selectivity between different tissues was due to differences in the efficacy of CEC inactivating the binding sites and not due to differences in binding affinity. To determine whether the effects on 125IBE 2254 binding reflected selective inactivation of functional receptors, contractile responses of rat spleen and vas deferens were examined. Pretreatment of intact tissues with 100 microM CEC for 30 min caused a large decrease in the potency and maximal contraction to norepinephrine in spleen but had no effect in vas deferens. Inhibition of specific 125IBE 2254 binding by various agonists and antagonists was determined in CEC-sensitive (liver, spleen) and insensitive (hippocampus, vas deferens) tissues. Although many drugs had similar affinities in all tissues, others were substantially less potent in the CEC-sensitive tissues. These experiments suggest that there are at least two subtypes of alpha 1-adrenergic receptors with different pharmacological properties in mammalian tissues, only one of which is inactivated by CEC.

Alpha 1-adrenoceptor subtypes linked to different mechanisms for increasing intracellular Ca2+ in smooth muscle

Receptor-mediated increases in intracellular Ca2+ levels can be caused by release from intracellular organelles and/or influx from the extracellular fluid. Noradrenaline (NA) released from sympathetic nerves acts on alpha 1-adrenoceptors to increase cytosolic Ca2+ and promote smooth muscle contraction. In many cells activation of alpha 1-adrenoceptors causes formation of inositol 1,4,5-trisphosphate which promotes Ca2+ release from intracellular stores. The mechanism by which receptor activation opens cell surface Ca2+ channels is not known, although in some cases it may be secondary to formation of inositol phosphates or release of stored intracellular Ca2+ (ref. 3). However, alpha 1-adrenoceptors have recently been shown to have different pharmacological properties in different tissues, and it has been proposed that different alpha 1-adrenoceptor subtypes may control mobilization of intracellular Ca2+ and gating of extracellular Ca2+ influx. We here report evidence for two subtypes of alpha 1-adrenoceptors which cause contractile responses through different molecular mechanisms. One subtype stimulates inositol phosphate (InsP) formation and causes contractions which are independent of extracellular Ca2+, and the other does not stimulate inositol phosphate formation and causes contractions which require the influx of extracellular Ca2+ through dihydropyridine-sensitive channels. These results suggest that neurotransmitters and hormones may control Ca2+ release from intracellular stores and influx through voltage-gated membrane channels through distinct receptor subtypes.

Neuropeptide Y potentiates contraction and inhibits relaxation of rabbit coronary arteries

The effects of neuropeptide Y (NPY) on contraction and relaxation of isolated rabbit coronary arteries were studied. NPY alone caused a weak contraction of coronary arteries with a mean EC50 value of 29 +/- 2.0 nM. Following exposure of coronary arteries to 30 nM NPY, the potencies of norepinephrine (in the presence of 3 microM timolol) and histamine in causing contraction were increased twofold, with no change in maximal contraction. After half-maximal contraction of coronary arteries with histamine and addition of 30 nM NPY, relaxation produced by norepinephrine (in the presence of 3 microM phentolamine), adenosine, and acetylcholine was inhibited. Concentration-response curves for all vasodilators were shifted to the right 10-22-fold by 30 nM NPY. Maximal relaxation caused by adenosine and norepinephrine was not changed by NPY, whereas the maximal response to acetylcholine was 37% less in the presence of NPY. Correlation of the tension produced by NPY with the shift in agonist contraction or relaxation concentration-response curves indicated that NPY-induced increases in baseline tone had no effect on the degree of shift in agonist concentration-response curves. These results show that NPY causes a modest potentiation of agonist-induced contraction and a dramatic blockade of vasodilator-induced relaxation of rabbit coronary arteries.