Altered response of human umbilical artery to 5-HT in gestational diabetic pregnancy.

The aim of this investigation was to evaluate serotonin (5-HT) action on isolated human umbilical arteries (HUA) from normal and gestational diabetes mellitus (GDM) pregnancies. 5-HT caused HUA contraction in a concentration-dependent manner in both investigated groups but with lower efficacy in GDM. After endothelial denudation or in the presence of indomethacin (cyclooxygenase inhibitor), the 5-HT-evoked response was comparably augmented, but only in arteries from uncomplicated pregnancies. 5-HT contractions were unchanged by L-NOARG (NO-synthase inhibitor) or glibenclamide (K(ATP) channel blocker) in both investigated groups. Whereas nifedipine (Ca(2+) channel blocker) reduced the contractile effect of 5-HT and was more potent in GDM, ouabain (Na(+)/K(+)-ATPase inhibitor) caused the contraction of HUA prior to 5-HT addition in both groups, but with a significantly reduced effect in GDM. In vascular rings from GDM, methiothepin (a 5-HT(1)/5-HT(2) receptor antagonist) significantly reduced 5-HT-induced contraction to a similar extent as compared to uncomplicated pregnancies. Ketanserin (a 5-HT(2A) receptor antagonist) produced a concentration-dependent inhibition of the 5-HT effect in GDM. In conclusion, in normal pregnancies, 5-HT produced a concentration- and endothelium-dependent contraction of HUA, most probably via endothelial prostacyclin. In contrast, the contractile effect of 5-HT in GDM was reduced with apparent endothelial dysfunction. In both normal and diabetic pregnancies, voltage-gated Ca(2+) channels and Na(+)/K(+)-ATPase contribute to the 5-HT-evoked contraction, as well to the regulation of basal vascular tone, but those actions were notably impaired in GDM. In uncomplicated and diabetic pregnancies, the transduction mechanism of 5-HT involves activation of mixed population of 5-HT(1) and 5-HT(2A) receptors in the HUA.

Analysis of the vasorelaxant action of angiotensin II in the isolated rat renal artery.

Taking into consideration that mechanisms involved in the vasodilatator actions of angiotensin II have not yet been completely elucidated, the present study was undertaken in order to examine the mechanisms underlying the angiotensin II-induced relaxation of rat renal artery (RRA). Angiotensin II produced concentration-dependent and endothelium-independent relaxation of isolated RRA. Angiotensin II-induced relaxation was partially reduced by inhibitors of nitric oxide synthase and guanylyl cyclase. The remaining dilatation was inhibited by a potassium channel blocker, charybdotoxin. Precontraction of RRA with high concentration of K(+) partially reduced angiotensin II-evoked relaxation, while indomethacin, glibenclamide, apamin and barium did not alter the angiotensin II concentration-response curve. Losartan had no effect on angiotensin II effect. Oppositely, HOE 140 and PD123319, separately or in combination, partially antagonized vasorelaxation induced by angiotensin II. Complete blockade of RRA response was obtained after simultaneous incubation of all three receptor antagonists HOE-140, PD123319, and losartan; L-NOARG plus HOE-140; or PD123319 plus charybdotoxin. These results indicate that angiotensin II produces endothelium-independent relaxation of RRA, which is most probably mediated by the interaction of the NO-cGMP pathway and K(+) channels. Moreover, we can assume that AT(1), AT(2), and B(2) receptors are involved in the vasorelaxant effect of angiotensin II.

Potassium channel opener pinacidil induces relaxation of the isolated human radial artery.

Taking into consideration that the search for drugs capable of modifying blood flow through human radial artery (RA) is warranted, the present study was designed to examine the vasodilatatory effects of the potassium channel opener, pinacidil on the RA and to define the contribution of different K+ -channel subtypes in the endothelium-independent pinacidil action on this blood vessel. Pinacidil relaxed the RA rings with endothelium and without endothelium with comparable potency. N-nitro-L-arginine methyl ester (L-NAME) and methylene blue did not affect the pinacidil-induced vasorelaxation in rings with endothelium. In the rings without endothelium, the K+ -channel blockers glibenclamide and tetraethylammonium (TEA) moderately antagonized the pinacidil-induced relaxation, while charybdotoxin and 4-aminopiridine did not. In endothelium-denuded rings, precontracted with 100 mM K+, the relaxant responses to pinacidil were highly significantly shifted to the right compared to those obtained in RA precontracted with phenylephrine, but pinacidil-induced maximal relaxation was not affected. Addition of nifedipine did not but addition of nifedipine and nickel (Na+ -Ca2+ exchanger inhibitor) did cause a statistically significant rightward shift of the pinacidil concentration-relaxation curve, although the effect 0.1 mM pinacidil was preserved. Thus, pinacidil induces relaxation of the human RA in endothelium-independent manner, and glibenclamide- and TEA-sensitive vascular smooth muscle K+ channels are probably involved. Its ability to completely relax the RA precontracted with K+ -rich solution suggests that pinacidil has additional K+ channel-independent mechanism(s) of action. It seems that stimulation of the forward mode of the Na+ -Ca2+ exchanger plays a part in this K+ channel-independent effect of pinacidil.

Pharmacological evaluation of bradykinin effect on human umbilical artery in normal, hypertensive and diabetic pregnancy.

The objective of this investigation was to compare bradykinin (BK) action on isolated intact or denuded human umbilical artery (HUA) in normal pregnancy, pregnancy-induced hypertension (PIH) and gestational diabetes mellitus (GDM). Bradykinin contracted HUA in a concentration-dependent manner in all investigated groups. Control BK contractions were unchanged by L-NOARG (NO-synthase inhibitor), glibenclamide (K(ATP) channel blocker), or des-Arg(9)(leu(8))-BK (B(1) antagonist), while were reduced by indomethacin (cyclooxygenase inhibitior) or nifedipine (Ca(2+) channel blocker). After endothelial denudation in GDM, concentration-response curve for BK was shifted to the left in relation to control HUA from normal pregnancy. OKY-046 (thromboxane A(2) -synthase inhibitor) displaced concentration-response curve for BK to the right in PIH, whereas reduction in maximal contraction was obtained in HUA from GDM. Ouabain (Na(+)/K(+)-ATPase inhibitor) contracted HUA prior to BK addition in all groups. Apamin (small conductance K(Ca) channel blocker), TEA (non-selectve K(+) channel blocker) or Ba(++) (K(IR)(+) channel blocker) augmented maximal BK contractions in normal pregnancy, PIH and GDM, respectively. HOE 140 (B(2) antagonist) produced concentration-dependent inhibition of BK effect in all groups. Collectively, in HUA from all groups BK evoked vasoconstriction via smooth muscle B(2) receptors. Intact endothelium provided additional modulation of BK contraction in GDM. Contribution of contractile cyclooxygenase products to BK action was demonstrated, and in PIH and GDM thromboxane A(2) was also involved. Voltage-gated Ca(2+) channels and Na(+)/K(+)-ATPase contribute to the BK contraction, and to the regulation of basal vascular tone, respectively. Diverse K(+) channels modulate BK contraction in HUA by preventing excessive vasoconstriction.

[Endothelial dysfunction: mechanisms of development and therapeutic options].

INTRODUCTION: Vascular endothelial cells play a key role in cardiovascular regulation by producing a number of potent vasoactive agents, including the vasodilator molecule nitric oxide (NO) and the vasoconstrictor peptide endothelin (ET). ENDOTHELIAL DYSFUNCTION: Endothelial dysfunction is recognized as the initial step in the atherosclerotic process. Impairment of NO synthesis, or increased inactivation of NO by superoxide radicals, may account for the increased periferal vascular tone, as well as contribute to the clinical consequences of different pathophysiological conditions which include vascular hypertrophy, increased platelet and monocyte adhesion to the endothelium, atherosclerosis, myocardial infarction and stroke. To date, most interventions attempting to improve endothelial dysfunction have targeted one or more of the numerous risk factors that can cause endothelial damage: hypertension (ACE inhibitors and calcium antagonists), hypercholesterolemia (lipid-lowering agents), cigarette smoking (cessation), sedentary lifestyle (increased physical activity), menopause (estrogen replacement therapy), and diabetes mellitus (control of metabolic abnormalities). Several pharmacologic agents have been suggested to achieve vascular protection through mechanisms that go beyond their primary therapeutic actions (ACE-and HMG-CoA reductase inhibitors). Beneficial changes to the endothelium might result from promotion of vasorelaxation, inhibition of vasoconstriction, reduction in the production of free radicals, or other mechanisms that protect the endothelium from injury. CONCLUSION: This study deals with the results of many experimental and clinical investigations. The possibility of using different classes of drugs was also established, including ACE inhibitors, Ca-antagonists, AT and endothelin receptor antagonists, direct activator of adenyl cyclase, statins, antioxidants, L-arginine, phosphodiesterase inhibitors, beta-blockers and organic nitrates.

Isolated rat inferior mesenteric artery response to adenosine: possible participation of Na+/K+-ATPase and potassium channels.

Adenosine (10(-7)-3 x 10(-4) M) produced concentration-dependent and endothelium-independent relaxation of isolated rat inferior mesenteric artery. Application of indomethacin (10(-5) M) or N(G)-nitro-L-arginine (10(-5) M) did did not alter adenosine-elicited relaxation. Conversely, in the presence of high concentration of K+ (100 mM), ouabain (10(-4)) or combination of tetraethylammonium (5 x 10(-4) M) and glibenclamide (10(-6) M), adenosine-evoked relaxant effect was significantly reduced. In K+-free solution, 1-3 mM potassium induced relaxation, which was partially reversed by ouabain (10(-4) M). 1,3-Dipropyl-8-cyclopentylxanthine (10(-9) M), an A1-receptor antagonist, did not affect adenosine-evoked relaxation. Oppositely, 8-(3-chlorostyryl)-caffeine (3 x 10(-7)-10(-6) M), a selective A2A receptor antagonist, significantly inhibited adenosine-induced relaxation in a concentration-dependent manner (pA2 = 6.74). These results indicate that in the isolated rat inferior mesenteric artery, adenosine produces endothelium-independent relaxation, which is partly induced by activation of smooth muscle adenosine A2A receptors, and further mediated by the activation of smooth muscle Na+/K+-ATPase and opening of mixed population of K+ channels.

[Therapeutic use of glucocorticoids and immunosuppressive agents].

Pharmacotherapy of autoimmune thyroid disease (AITD) is complex. Apart from the replacement hormone therapy, antithyroid agents, beta adrenoceptor blockers and other drugs, in regard to the present symptoms, it also includes the administration of glucocorticoids and immunosuppressive agents. Physiological actions of glucocorticoids are significant in number, well known and described in details. The most prominent pharmacological properties of glucocorticoids, that are important fortheir clinical use, are antiinflammatory and immunosuppressive actions. In this article, the most notable clinical pharmacology aspects of glucocorticoids have been presented, including the basic principles of their therapeutic use, as well as the most important indications with the examples of dosing regiments (rheumatic disorders, renal diseases, allergic reactions, bronchial asthma, gastrointestinal inflammatory diseases, thrombocytopenia, organ transplantation, and Graves' ophthalmopathy). In addition, adverse and toxic effects of glucocorticoids as well as their interactions with other drugs have been described. Immunosuppressive agents have important role in treatment of immune disorders, including the reduction of immune response in autoimmune diseases and organ transplantation. Apart from glucocorticoids, immunosuppressive agents consist of calcineurin inhibitors (cyclosporine, tacrolimus), antiproliferative and antimetabolic agents (sirolimus, azathioprine, mycophenolate mofetil, methotrexate, cyclophosphamide), monoclonal antibodies: anti-CD3 antibody (muromonab-CD3), anti-CD25 antibody (daclizumab), anti-TNF-alpha antibody (infliximab). In this part, the most updated facts about mechanism of action, rational therapeutic use, as well as adverse and toxic effects of immunosuppressive agents have been reviewed.

Effect of the vascular endothelium on contractions induced by noradrenaline and phenylephrine in perforating branch of the human internal mammary artery.

The effects of noradrenaline (Nor) and phenylephrine (Phe) on the isolated, non-precontracted perforating branch of the human internal mammary artery (HIMA) were investigated. Nor and Phe induced concentration-dependent contractions of intact and endothelium-denuded arterial rings with no statistically significant differences between the pEC(30) and maximal response values. The pretreatment of arterial rings with indomethacin had no effect on Nor- and Phe-induced contractions of both, intact and endothelium-denuded preparations. The pre-addition of L-NMMA did not affect contractions of perforating branch of the HIMA evoked by Nor, but provoked significant potentiation of Phe-induced contractions of perforating branch of the HIMA both intact and denuded of endothelium only at Phe concentration higher than 3 x 10(-6)M. The effects of selective alpha1-adrenoceptor antagonist, prazosin and selective alpha2-adrenoceptor antagonist, rauwolscine were concentration-dependent, and they induced a significant shift to the right (for both studied antagonists) of the concentration-response curves for Nor in both preparations with or without endothelium. The effects of prazosin and rauwolscine on the concentration-response curves for Phe were similar. In conclusion, this study has shown that Nor and Phe induce concentration-dependent contractions of the perforating branch of the HIMA. Removal of the endothelium did not modify this effect. Products of cyclooxygenase pathway had no influence on Nor and Phe action. Endothelium derived nitric oxide (NO) had no modulatory effect of Nor-induced contractions, but inhibition of NO synthesis provoked potentiation of Phe-induced contractions either in intact or endothelium-denuded preparations. The mechanism of this effect remains still unclear. On the basis of differential affinity of the antagonists and affinities of Nor and Phe themselves, we suggest that alpha1-adrenoceptor subtype is probably involved in the Nor- and Phe-induced contraction of the perforating branch of the HIMA both intact or denuded of endothelium.

Analysis of adenosine vascular effect in isolated rat aorta: possible role of Na+/K+-ATPase.

The present experiments were undertaken in order to examine the effect of adenosine in isolated rat aorta, to investigate the possible role of intact endothelium and endothelial relaxing factors in this action and to determine which population of adenosine receptors is involved in rat aorta response to adenosine. Adenosine (0.1-300 microM) produced concentration-dependent (intact rings: pD2=4.39+/-0.09) and endothelium-independent (denuded rings: pD2=4.52+/-0.12) relaxation of isolated rat aorta. In the presence of high concentration of K+ (100 mM) adenosine-evoked relaxation was significantly reduced (maximal relaxation in denuded rings: control - 92.1+/-9.8 versus K+- 54.4+/-5.0). Similar results were obtained after incubation of ouabain (100 microM) or glibenclamide (1 microM). In K+-free solution, K+ (1-10 mM)-induced rat aorta relaxant response was significantly inhibited by ouabain (100 microM). Application of indomethacin (10 microM), NG-nitro-L-arginine (10 microM) or tetraethylammonium (500 microM) did not alter the adenosine-elicited effect in rat aorta. 8-(3-Chlorostyril)-caffeine (0.3-3 microM), a selective A2A-receptor antagonist, significantly reduced adenosine-induced relaxation of rat aorta in a concentration-dependent manner (pKB=6.57). Conversely, 1,3-dipropyl-8-cyclopentylxanthine (10 nM), an A1-receptor antagonist, did not affect adenosine-evoked dilatation. These results indicate that in isolated rat aorta, adenosine produces endothelium-independent relaxation, which is most probably dependent upon activation of smooth muscle Na+/K+-ATPase, and opening of ATP-sensitive K+ channels, to a smaller extent. According to receptor analysis, vasorelaxant action of adenosine in rat aorta is partly induced by activation of smooth muscle adenosine A2A receptors.

Influence of the endothelium on the vasorelaxant response to acetylcholine and vasoactive intestinal polypeptide in the isolated rabbit facial artery.

The aim was to examine the influence of the endothelium on acetylcholine (ACh) and vasoactive intestinal polypeptide (VIP) functional responses in the isolated glandular branch of rabbit facial artery precontracted with phenylephrine as well as the potential contribution of nitric oxide (NO) and prostanoids in the ACh- and VIP-induced effects. Acetylcholine caused endothelium-dependent and VIP endothelium-independent relaxations of facial artery. The effect of ACh was partly inhibited by NG-monomethyl-l-arginine (l-NMMA, a non-selective NO synthase inhibitor) or by indomethacin (a cyclooxygenase inhibitor) while being completely blocked after concomitant addition of l-NMMA and indomethacin. The relaxation of the facial artery caused by ACh was unaffected by 65 mm KCl. The VIP-induced vasodilation was potentiated by forskolin (an adenylate cyclase stimulator) and partly reduced by l-NMMA or S-methyl-l-thiocitrulline (l-SMTC, a neuronal NO synthase inhibitor), whereas it was unaffected by indomethacin. These results suggest that ACh effects on the rabbit facial artery are mediated through release of endothelium-derived NO and cyclooxygenase products, while the effect of VIP is most probably mediated by an increase of cyclic adenosine 3',5'-monophosphate (cAMP) in vascular smooth muscles and by VIP-induced release of NO from perivascular nerve fibers.