1 We examined whether x1-adrenoceptors in various blood vessels can be divided into subtypes by antagonist affinity or by susceptibility to chloroethylclonidine or nifedipine. 2 Noradrenaline or phenylephrine produced concentration-dependent contractions in all the tissues tested, which were competitively inhibited by phentolamine, yohimbine, prazosin, WB4101 and HV723. However, there were large differences between the tissues in the pA2 values for all the antagonists except phentolamine. 3 The blood vessels could be classified into three groups (I, II and III) on the basis of their affinity variation. In group I (dog mesenteric artery and vein, saphenous vein), the pA2 values for HV723 were greater than 9, and those for HV723 and WB4101 were approximately 1 log unit higher than for prazosin.This rank order of affinity reversed in group II (dog carotid artery and rat thoracic aorta), where prazosin was more potent (pA2 values greater than 9.5) than HV723 or WB4101. In group III (rabbit mesenteric artery, thoracic aorta and carotid artery and guinea-pig thoracic aorta), on the other hand, prazosin, HV723 and WB4101 inhibited the noradrenaline response with a similar affinity (pA2 values ranging from 8 to 9). 4 Yohimbine inhibited the responses to noradrenaline and phenylephrine with a lower affinity than prazosin, HV723 or WB4101. The pA2 values for yohimbine were similar in groups I and II (the values greater than 6.5), which were greater than those in group III (values less than 6.4).5 The al-adrenoceptors in group II were selectively affected by chlorethylclonidine, resulting in an irreversible attenuation of noradrenaline responses in the dog carotid artery and a persistent contraction in the rat thoracic aorta.6 Nifedipine either produced no effect or a slight inhibition of al-adrenoceptor-mediated contractions in all the blood vessels; these effects were not correlated to the above groups.7 These results suggest that a,-adrenoceptors of blood vessels can be divided into three subtypes (designated as a1H, 04L and a1N) by antagonist affinity and their susceptibility to chloroethylclonidine but not to nifedipine: the characteristics of each subtype are summarized in Table 3. Subtypes oelH, oL and UlN may be predominantly involved in the contractile responses to noradrenaline or phenylephrine of the blood vessels in groups II, III and I, respectively.

No abstract

Leukocytosis in tobacco smokers has been well recognized; however, the exact cause has not been elucidated. To test the hypothesis that tobacco nicotine stimulates neutrophils in the respiratory tract to produce IL-8, which causes neutrophilia in vivo, we examined whether nicotine induces neutrophil-IL-8 production in vitro; the causative role of NF-kappaB in its production, in association with the possible production of reactive oxygen intermediates that activate NF-kappaB; and the nicotinic acetylcholine receptors (nAChRs) involved in IL-8 production. Nicotine stimulated neutrophils to produce IL-8 in both time- and concentration-dependent manners with a 50% effective concentration of 1.89 mM. A degradation of IkappaB-alpha/beta proteins and an activity of NF-kappaB p65 and p50 were enhanced following nicotine treatment. The synthesis of superoxide and the oxidation of dihydrorhodamine 123 (DHR) were also enhanced. The NOS inhibitor, nomega-Nitro-l-arginine methyl ester, prevented nicotine-induced IL-8 production, with an entire abrogation of DHR oxidation, IkappaB degradation, and NF-kappaB activity. Neutrophils spontaneously produced NO whose production was not increased, but rather decreased by nicotine stimulation, suggesting that superoxide, produced by nicotine, generates peroxynitrite by reacting with preformed NO, which enhances the NF-kappaB activity, thereby producing IL-8. The nAChRs seemed to be involved in IL-8 production. In smokers, blood IL-8 levels were significantly higher than those in nonsmokers. In conclusion, nicotine stimulates neutrophil-IL-8 production via nAChR by generating peroxynitrite and subsequent NF-kappaB activation, and the IL-8 appears to contribute to leukocytosis in tobacco smokers.

These results suggest the presence of at least two distinct alpha 1-adrenoceptor subtypes (presumably an alpha 1C subtype with a high affinity for prazosin and WB4101, and a putative alpha 1L subtype with a low affinity for the antagonists) in the human prostate, in which the latter subtype may be predominantly involved in the contractile response to noradrenaline.