Different ß-adrenoceptor subtypes coupling to cAMP or NO/cGMP pathways: implications in the relaxant response of rat conductance and resistance vessels.

BACKGROUND AND PURPOSE: To analyse the relative contribution of ß1 -, ß2 - and ß3 -adrenoceptors (Adrb) to vasodilatation in conductance and resistance vessels, assessing the role of cAMP and/or NO/cGMP signalling pathways. EXPERIMENTAL APPROACH: Rat mesenteric resistance artery (MRA) and aorta were used to analyse the Adrb expression by real-time-PCR and immunohistochemistry, and for the pharmacological characterization of Adrb-mediated activity by wire myography and tissue nucleotide accumulation. KEY RESULTS: The mRNAs and protein for all Adrb were identified in endothelium and/or smooth muscle cells (SMCs) in both vessels. In MRA, Adrb1 signalled through cAMP, Adrb3 through both cAMP and cGMP, but Adrb2, did not activate nucleotide formation; isoprenaline relaxation was inhibited by propranolol (ß1 , ß2 ), CGP20712A (ß1 ), and SQ22536 (adenylyl cyclase inhibitor), but not by ICI118,551 (ß2 ), SR59230A (ß3 ), ODQ (soluble guanylyl cyclase inhibitor), L-NAME or endothelium removal. In aorta, Adrb1 signalled through cAMP, while ß2 - and ß3 -subtypes through cGMP; isoprenaline relaxation was inhibited by propranolol, ICI118,551, ODQ, L-NAME, and to a lesser extent, by endothelium removal. CL316243 (ß3 -agonist) relaxed aorta, but not MRA. CONCLUSION AND IMPLICATION: Despite all three Adrb subtypes being found in both vessels, Adrb1, located in SMCs and acting through the adenylyl cyclase/cAMP pathway, are primarily responsible for vasodilatation in MRA. However, Adrb-mediated vasodilatation in aorta is driven by endothelial Adrb2 and Adrb3, but also by the Adrb2 present in SMCs, and is coupled to the NO/cGMP pathway. These results could help to understand the different physiological roles played by Adrb signalling in regulating conductance and resistance vessels.

[Role of antithrombin iii in cardiac surgery]. / Papel de la antitrombina iii en cirugía cardiaca.

Coagulation of blood is of multidisciplinary interest. Cardiac surgery produces major changes in the delicate balance between pro-and anti-coagulant serum factors. The role of antithrombin iii has been analysed after finding evidence that associated decreased levels of protein activity to postoperative morbidity and mortality. Supplementing exogenous antithrombin is considered with the aim of optimising outcomes. Its intrinsic anticoagulant and anti-inflammatory properties have stimulated a growing interest, and suggests new lines of research.

Multiple actions of glaucine on cyclic nucleotide phosphodiesterases, alpha 1-adrenoceptor and benzothiazepine binding site at the calcium channel.

1. In the present study, the properties of glaucine (an aporphine structurally related to papaverine) were compared with those of papaverine, diltiazem, nifedipine and prazosin. The work includes functional studies on rat isolated aorta contracted with noradrenaline, caffeine or KCl, and a determination of the affinity of glaucine at calcium channel binding sites of alpha-adrenoceptors, by use of [3H]-(+)-cis-diltiazem, [3H]-nitrendipine and [3H]-prazosin binding to cerebral cortical membranes. The effects of glaucine on the different molecular forms of cyclic nucleotide phosphodiesterases (PDE) isolated from bovine aorta were also determined. 2. Contraction evoked by noradrenaline (1 microM) or depolarizing solution (60 mM KCl) were inhibited in a concentration-dependent manner by all the compounds tested. As expected, prazosin showed a greater selectivity of action on NA-induced contraction, whereas nifedipine and diltiazem appeared more potent on KCl-induced contraction. Glaucine had a greater potency on the contraction elicited by noradrenaline whereas papaverine acted non specifically. 3. In Ca(2+)-free solution, prazosin (0.1 microM) and glaucine (0.1 mM) inhibited the contraction evoked by NA; diltiazem (0.1 mM) diminished this contraction whereas nifedipine (1 microM) had no effect. Preincubation of tissues with glaucine, diltiazem, nifedipine and prazosin did not modify the contractile response induced by caffeine. In contrast, papaverine (0.1 mM) significantly inhibited the contractions evoked by NA or caffeine in Ca(2+)-free medium. 4. Glaucine and papaverine show affinity at the [3H]-prazosin binding site and at the benzothiazepine binding site of the Ca(2+)-channel receptor complex, but have no effect at the dihydropyridine binding site in rat cerebral cortex. Glaucine exerts some selectivity as an inhibitor of [3H]-prazosin binding as opposed to [3H]-(+ )-cis-diltiazem binding while papaverine appears to have approximately equal affinity in this respect.5. This study confirms the presence of four phosphodiesterase (PDE) activities in bovine aorta: a calmodulin-activated PDE (CaM-PDE type I) which hydrolyzed preferentially guanosine 3':5'-cyclic monophosphate (cyclic GMP); a cyclic GMP selective form (cGMP-PDE type V); and two low Km adenosine 3':5'-cyclic monophosphate (cyclic AMP) PDEs that are insensitive to the stimulatory effect of CaM, one of which was inhibited by cyclic GMP (CGI-PDE, type III) and the other by rolipram (cAMP-PDE, type IV). Glaucine selectively inhibits one of the two forms of Ca2+-independent low Km cAMP-PDE, the type IV. In contrast, papaverine exerts a non-selective inhibitory effect upon all PDE forms.6. The present work provides evidence that glaucine, a benzyltetrahydroisoquinoline alkaloid, has interesting properties as an alpha l-adrenoceptor antagonist, calcium entry blocker (through the benzothiazepine recognition site in the calcium channel) and as a selective inhibitor of the rolipram-sensitive cAMP-PDE, type IV PDE.

Selective inhibition of calcium entry induced by benzylisoquinolines in rat smooth muscle.

The mechanism of relaxant activity of six benzylisoquinolines was examined in order to determine the minimal structural requirements that enable these compounds to have either a non-specific action like papaverine or an inhibitory activity on calcium entry via potential-operated channels. All the alkaloids tested totally or partially relaxed KCl-depolarized rat uterus and inhibited oxytocin-induced rhythmic contractions. Only glaucine and laudanosine inhibited K(+)-induced uterine contractions more than oxytocin-induced uterine contractions. In Ca(+)-free medium, sustained contractions induced by oxytocin or vanadate were relaxed by the alkaloids tested except for glaucine and laudanosine indicating no inhibitory effect on intracellular calcium release. Those alkaloids containing an unsaturated heterocyclic ring (papaverine, papaverinol, papaveraldine, N-methylpapaverine and dehydropapaverine) exhibited a more specific activity than those with a tetrahydroisoquinoline ring.

Role of intracellular calcium stores in the contractile response of uterus to several agonists.

A comparison was made of contractions produced by submaximal doses of oxytocin, noradrenaline, PGE2 and PGF2 alpha in estrogen-dominated rat uterus after the preparation had been loaded in Ca-free medium supplemented with EDTA 3 mM. The experiments were carried out in the presence of EDTA 1 mM to complex the contaminating Ca. The contraction was sustained as long as the preparation was exposed to the drug and was relaxed by washing. Cumulative concentration-response curves to oxytocin (6.25-100 microM), noradrenaline (0.05-1.6 mM), PGE2 (0.1-1.6 microM) and PGF2 alpha (0.02-0.32 microM) were made. The threshold concentration for PGF2 alpha was much lower than for PGE2, oxytocin and noradrenaline. Isoprenaline (10- -10(-4)M), KCl (56.3 mM) and caffeine (5 mM) were added. The results showed that isoprenaline and KCl did not produce contractile response. Caffeine produces only a small decrease in the resting tension and this effect is not reversible. After addition of noradrenaline, a concentration of oxytocin (6 microM) produced a uterine contraction smaller than the control response of uterus to oxytocin. The response to the oxytocin applied after washing out the caffeine was the same as the control response. All agonists tested that were capable of inducing uterine contraction in Ca-free medium act through specific receptors. This suggests a relation between receptor-operated Ca-channels and intracellular Ca-stores.