Pathophysiology and therapeutic possibilities of calcitonin gene-related peptide in hypertension.

Calcitonin gene related peptide (CGRP), a 37 amino acid neuropeptide, is the most potent vasodilator known. Participation of CGRP in hypertension and related diseases, such as preeclampsia or vasospasm after subarachnoid haemorrage, is one of the most studied topics. In this review we summarize the published roles of CGRP in pathophysiology of hypertension in humans and in experimental models. We also discuss the effects of direct administration of CGRP in the treatment of hypertension and of anti-hypertensive drugs that enhance the release or response of endogenous calcitonin gene-related peptide: angiotensin converting enzyme inhibitors, selective antagonists for the angiotensin II receptor, beta-blockers, magnesium sulphate for preeclampsia and rutaecarpine, as well as the possibilities using CGRP in gene therapy for prevention of vasospasm after subarachnoid haemorrage.

Pathophysiology and therapeutic possibilities of calcitonin gene-related peptide in hypertension

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Calcitonin gene related peptide (CGRP), a 37 amino acid neuropeptide, is themost potent vasodilator known. Participation of CGRP in hypertension and relateddiseases, such as preeclampsia or vasospasm after subarachnoid haemorrage, is one ofthe most studied topics. In this review we summarize the published roles of CGRPin pathophysiology of hypertension in humans and in experimental models. We alsodiscuss the effects of direct administration of CGRP in the treatment of hypertensionand of anti-hypertensive drugs that enhance the release or response of endogenouscalcitonin gene-related peptide: angiotensin converting enzyme inhibitors, selectiveantagonists for the angiotensin II receptor, beta-blockers, magnesium sulphate forpreeclampsia and rutaecarpine, as well as the possibilities using CGRP in gene therapyfor prevention of vasospasm after subarachnoid haemorrage

Human umbilical vein: involvement of cyclooxygenase-2 pathway in bradykinin B1 receptor-sensitized responses.

In isolated human umbilical vein (HUV), the contractile response to des-Arg9-bradykinin (des-Arg9-BK), selective BK B1 receptor agonist, increases as a function of the incubation time. Here, we evaluated whether cyclooxygenase (COX) pathway is involved in BK B1-sensitized response obtained in 5-h incubated HUV rings. The effect of different concentrations of indomethacin, sodium salicylate, ibuprofen, meloxicam, lysine clonixinate or NS-398 administrated 30 min before concentration-response curves (CRC) was studied. All treatments produced a significant rightward shift of the CRC to des-Arg9-BK in a concentration-dependent manner, which provides pharmacological evidence that COX pathway is involved in the BK B1 responses. Moreover, in this tissue, the NS-398 pKb (5.2) observed suggests that COX-2 pathway is the most relevant. The strong correlation between published pIC50 for COX-2 and the NSAIDs' pKbs estimated further supports the hypothesis that COX-2 metabolites are involved in BK B1 receptor-mediated responses. In other rings, indomethacin (30, 100 micromol/l) or NS-398 (10, 30 micromol/l) produced a significant rightward shift of the CRC to BK, selective BK B2 agonist, and its pKbs were similar to the values to inhibit BK B1 receptor responses, suggesting that COX-2 pathway also is involved in BK B2 receptor responses. Western blot analysis shows that COX-1 and COX-2 isoenzymes are present before and after 5-h in vitro incubation and apparently COX-2 does not suffer additional induction.

Retinoids inhibit bradykinin B1 receptor-sensitized responses in human umbilical vein.

Bradykinin B1 receptors are not expressed under physiological conditions but are induced under inflammatory conditions. In isolated human umbilical vein, a spontaneous bradykinin B1 receptor sensitization process has been demonstrated. On the other hand, retinoids have been shown to exert anti-inflammatory and immunomodulatory actions. We have now examined the effects of all-trans-retinoic acid and 9-cis-retinoic acid on the bradykinin B1 receptor-sensitized responses in human umbilical vein. Both retinoids produced a concentration-dependent rightward shift of the concentration-response curves for the bradykinin B1 receptor agonist, des-Arg(9)-bradykinin. Retinoid treatment did not modify the responses to bradykinin B1 receptor-unrelated agonists, bradykinin or serotonin. In conclusion, retinoids inhibit bradykinin B1 receptor-sensitized responses and this action could participate in their anti-inflammatory and immunomodulatory effects.

Bradykinin B1 receptor in isolated human umbilical vein: an experimental model of the in vitro up-regulation process.

Bradykinin (BK) B1 receptors are not normally expressed in physiological conditions but could be induced in immunopathological states. Molecular approaches have confirmed that BK B1 receptor gene is transcriptionally induced in injured tissues. In these situations, the cytokine network and other proinflammatory mediators are close linked to BK B1 receptor expression. In this article, we describe the functional characterization of the BK B1 receptor up-regulation process in the isolated human umbilical vein and the pharmacological tools employed to demonstrate the de novo synthesis of these receptors. BK B1 receptors are up-regulated in a time- and protein synthesis-dependent process. Furthermore, in this tissue we have demonstrated the close link between the BK B1 receptor sensitization and proinflammatory cytokines, such as interleukin-1 beta and tumor necrosis factor-alpha. We also discuss the possible relationship between nuclear factor-kappa B and BK B1 receptor induction in human umbilical vein.

[Quinolones: historic review]. / Quinolonas. Revisión histórica.

The pharmacotherapeutic development of quinolones was produced in the last three decades. In 1965, the first commercial product was nalidixic acid (first-generation quinolone) an then, chemists have been able to synthesize several thousands of quinolone molecules's derivatives modifying primarily at the N-1 position and at the C-6, C-7 and C-8 positions. The structural changes incorporated into these new compounds enhanced pharmacodynamic characteristics and pharmacokinetic profiles. Third-generation quinolones (levofloxacin, clinafloxacin, sparfloxacin, grepafloxacin, DU-6859a and trovafloxacin) have several advantages over first-generation quinolones (nalicixic acid, cinoxacin and oxolinic acid) and second-generation quinolones (norfloxacin, enoxacin, ciprofloxacin, pefloxacin, ofloxacin, lomefloxacin and fleroxacin). The new fluroquinolones are well absorbed in the duodenum and jejunum. They have large volumes of distribution and their penetration into different tissues and body fluids in humans has been demonstrated, reaching concentrations equal to or greater than those observed in plasma. The third-generation quinolones are broad-spectrum antimicrobials with an improved in vitro potency against gram-positive and gram-negative bacteria, including anaerobes and intracellular pathogens.

Further pharmacological characterization of bradykinin B1 receptor up-regulation in human umbilical vein.

Previous reports have provided evidence to support the view that the de novo synthesis of bradykinin (BK) B(1) receptor is involved in the induction of vascular responses in human umbilical vein (HUV). In the present study, we evaluated different pharmacological tools to further analyze this up-regulation process in HUV. Concentration-response curves to des-Arg(9)-BK, a selective BK B(1) receptor agonist, were performed after 5 h of incubation. Tumor necrosis factor-alpha potentiated BK B(1) receptor responses at 5 h without modifying the maximal response to des-Arg(9)-BK. Pyrrolidine dithiocarbamate, an inhibitor of nuclear factor-kappaB activation, produced a concentration-dependent decrease of the BK B(1) receptor sensitization. When tissues were continuously exposed to actinomycin D, a transcription inhibitor, or cycloheximide, a protein synthesis inhibitor, concentration-response curves to des-Arg(9)-BK were markedly diminished. On the other hand, transitory exposure to cycloheximide allowed the full recovery of BK B(1) receptor-sensitized responses at 5 h. Finally, continuous incubation with the N-linked glycosylation inhibitor, tunicamycin, almost completely abolished des-Arg(9)-BK-mediated responses. In summary, this sensitization process is potentiated by tumor necrosis factor-alpha and is selectively inhibited by pyrrolidine dithiocarbamate, suggesting that BK B(1) receptor up-regulation in HUV involves nuclear factor-kappaB activation. The effects of actinomycin D and tunicamycin provide evidence that the de novo synthesis of a transmembrane glycoprotein has an obligatory role in the BK B(1) up-regulation. The reversion of the cycloheximide effect on BK B(1) response indicates that the time necessary for synthesis, trafficking, and functional membrane expression of this receptor would be less than 1 h.

Characterization of alpha1-adrenoceptor subtypes mediating vasoconstriction in human umbilical vein.

1. The present study attempted to characterize pharmacologically the subtypes of alpha-adrenoceptors mediating contractions in human umbilical vein (HUV). 2. HUV rings were mounted in isolated organ baths and cumulative concentration-response curves were constructed for the alpha-adrenoceptor agonists phenylephrine and adrenaline. Adrenaline was more potent than phenylephrine (pD2=7.29 and 6.04 respectively). 3. Isoproterenol exhibited no agonism on KCl pre-contracted HUV rings. Propranolol (1 microM) and rauwolscine (0.1 microM) did not affect the concentration-response curves to adrenaline. These results demonstrate the lack of involvement of functional beta-or alpha2-adrenoceptors in adrenaline-induced vasoconstriction. 4. The non subtype selective alpha1-adrenoceptor antagonist prazosin was evaluated on phenylephrine and adrenaline concentration-response curves. The effects of the competitive alpha1A and alpha1D-adrenoceptor antagonists, 5-methyl urapidil and BMY 7378 and the irreversible alpha1B selective compound chloroethylclonidine (CEC) were also evaluated on adrenaline concentration-response curves. 5. The potencies of prazosin against responses mediated by adrenaline (pA2= 10.87) and phenylephrine (pA2= 10.70) indicate the involvement of prazosin-sensitive functional alpha1-adrenoceptor subtype in vasoconstriction of the HUV. 6. The potencies of 5-methyl urapidil (pA2 = 6.70) and BMY 7378 (pA2= 7.34) were not consistent with the activation of an alpha1A- or alpha1D-adrenoceptor population. 7. Exposure to a relatively low CEC concentration (3 microM) abolished the maximum response to adrenaline suggesting that this response was mediated by an alpha1B-adrenoceptor subtype. 8. We conclude that HUV express a prazosin-sensitive functional alpha1-adrenoceptor resembling the alpha1B-subtype according with the low pA2 values for both 5-methyl urapidil and BMY 7378 and the high sensitivity to CEC.

Quinolonas. Revisión histórica. / [Quinolones: historic review]

The pharmacotherapeutic development of quinolones was produced in the last three decades. In 1965, the first commercial product was nalidixic acid (first-generation quinolone) an then, chemists have been able to synthesize several thousands of quinolone moleculess derivatives modifying primarily at the N-1 position and at the C-6, C-7 and C-8 positions. The structural changes incorporated into these new compounds enhanced pharmacodynamic characteristics and pharmacokinetic profiles. Third-generation quinolones (levofloxacin, clinafloxacin, sparfloxacin, grepafloxacin, DU-6859a and trovafloxacin) have several advantages over first-generation quinolones (nalicixic acid, cinoxacin and oxolinic acid) and second-generation quinolones (norfloxacin, enoxacin, ciprofloxacin, pefloxacin, ofloxacin, lomefloxacin and fleroxacin). The new fluroquinolones are well absorbed in the duodenum and jejunum. They have large volumes of distribution and their penetration into different tissues and body fluids in humans has been demonstrated, reaching concentrations equal to or greater than those observed in plasma. The third-generation quinolones are broad-spectrum antimicrobials with an improved in vitro potency against gram-positive and gram-negative bacteria, including anaerobes and intracellular pathogens.

Bradykinin B1 receptors in human umbilical vein: pharmacological evidence of up-regulation, and induction by interleukin-1 beta.

Bradykinin B1 receptor-mediated responses increase as a function of in vitro incubation in the human umbilical vein. When tissues were continuously treated with the protein synthesis inhibitor, cycloheximide, or with the protein trafficking inhibitor, brefeldin A, pEC50 and maximal response to the selective bradykinin B1 receptor agonist, des-Arg9-bradykinin, were significantly diminished. The anti-inflammatory steroid, dexamethasone, produced a rightward shift of the concentration-response curve to des-Arg9-bradykinin, without affecting the maximal response. Furthermore, lipopolysaccharide or recombinant human interleukin-1 beta potentiate the bradykinin B1-sensitized responses, showing a leftward shift of the concentration-response curve to des-Arg9-bradykinin, without modifying the maximal response. On the other hand, bradykinin B2 receptor-mediated responses were unaffected by continuous exposure to cycloheximide, dexamethasone or lipopolysaccharide. These results provide pharmacological evidence to support the view that the de novo synthesis of bradykinin B1 receptors is involved in the induction of vascular responses in the human umbilical vein. This up-regulation process seems to be selective for bradykinin B1 receptors. The inhibitory effect of dexamethasone and the potentiating actions of lipopolysaccharide and exogenous human recombinant interleukin-1 beta on des-Arg9-bradykinin-mediated responses, suggest the possible role of interleukin-1 beta in the bradykinin B1 receptor up-regulation phenomenon in human umbilical vein.

Bradykinin B1 receptors in human umbilical vein.

The present study was undertaken to demonstrate the presence of bradykinin B1 receptors mediating contraction of human umbilical vein. The bradykinin B1 receptor selective agonist, des-Arg9-bradykinin, produced a dose-dependent contractile response of human umbilical vein rings. Furthermore, des-Arga-bradykinin-mediated response increased in a time-dependent manner in vitro. The maximal response to des-Arg9-bradykinin, expressed as percentage of the maximum elicited by serotonin, was: 10 +/- 2 at 15 min, 55 +/- 5 at 120 min and 80 +/- 3 at 300 min. Des-Arg9-bradykinin-mediated contractions were inhibited by the specific bradykinin B1 receptor antagonist des-Arg9-[Leu8]bradykinin which produced parallel shifts in the dose-response curve to the selective bradykinin B1 receptor agonist. Schild regression analysis of data established a pA2 value of 6.16 +/- 0.06. Kinin-induced contraction was not modified by pre-treatment with indomethacin (10 microM), a cyclo-oxygenase inhibitor. On the other hand, continuous exposure to the anti-inflammatory steroid dexamethasone (100 microM) or to the protein synthesis inhibitor cycloheximide (70 microM) largely prevented the sensitization to des-Arg9-bradykinin in incubated human umbilical vein rings. These results confirm the presence of bradykinin B1 receptors which mediate contraction in isolated human umbilical vein. These responses are up-regulated in a time- and protein synthesis-dependent process.

[Amplification of contractile response by serotonin on noradrenaline in the human umbilical artery]. / Amplificación de la respuesta contractil a noradrenalina por serotonina en la arteria umbilical humana.

A progressive increase in plasma levels of serotonin (5-HT) during pregnancy has been reported. Furthermore, an increase in the concentration of noradrenaline (NA) has been described during labor. On the other hand, in different arteries it has been observed that minimal effective concentrations of 5-HT are able to produce an increase or "amplification" of the contractile response to a second agonist. From these reports, it seemed interesting to determine the existence of a synergistic interaction between 5-HT and NA in the human umbilical artery (HUA), and the probable mechanisms involved. Therefore, strips of HUA were incubated in Krebs solution at 37 degrees C and gassed with a mixture of CO2 (5%) and O2 (95%). The contractile isometric response was assessed. After a period of two hours, complete cumulative concentration-response curves to 5-HT and to NA were obtained. The maximal contractile response to NA was approximately 20% of the maximal response to 5-HT. In another series of experiments, the response to NA was enhanced by previous treatment with minimal effective doses of 5-HT (control response 0.24 +/- 0.06 g; "amplified" response 0.53 +/- 0.06 g, P < 0.01). This "amplified" response to NA was correlated with the degree of previous contraction with 5-HT, when the last was between 3 and 30% of the maximal response. However, precontractions higher than 40% abolished the responses to NA. In other experiments, the artery strips were incubated during thirty minutes with diltiazem 1 microM before agonists addition. In this condition, a decrease in the control and amplified response was observed. Therefore, we have shown the existence of an amplifying effect of 5-HT over the response to NA in the HUA, and we discuss the possible mechanisms involved and the possible clinical relevance in preeclampsia.

Amplificación de la respuesta contractil a noradrenalina por serotonina en la arteria umbilical humana. / [Amplification of contractile response by serotonin on noradrenaline in the human umbilical artery]

A progressive increase in plasma levels of serotonin (5-HT) during pregnancy has been reported. Furthermore, an increase in the concentration of noradrenaline (NA) has been described during labor. On the other hand, in different arteries it has been observed that minimal effective concentrations of 5-HT are able to produce an increase or [quot ]amplification[quot ] of the contractile response to a second agonist. From these reports, it seemed interesting to determine the existence of a synergistic interaction between 5-HT and NA in the human umbilical artery (HUA), and the probable mechanisms involved. Therefore, strips of HUA were incubated in Krebs solution at 37 degrees C and gassed with a mixture of CO2 (5

) and O2 (95

). The contractile isometric response was assessed. After a period of two hours, complete cumulative concentration-response curves to 5-HT and to NA were obtained. The maximal contractile response to NA was approximately 20

of the maximal response to 5-HT. In another series of experiments, the response to NA was enhanced by previous treatment with minimal effective doses of 5-HT (control response 0.24 +/- 0.06 g; [quot ]amplified[quot ] response 0.53 +/- 0.06 g, P < 0.01). This [quot ]amplified[quot ] response to NA was correlated with the degree of previous contraction with 5-HT, when the last was between 3 and 30

of the maximal response. However, precontractions higher than 40

abolished the responses to NA. In other experiments, the artery strips were incubated during thirty minutes with diltiazem 1 microM before agonists addition. In this condition, a decrease in the control and amplified response was observed. Therefore, we have shown the existence of an amplifying effect of 5-HT over the response to NA in the HUA, and we discuss the possible mechanisms involved and the possible clinical relevance in preeclampsia.

Decrease of extracellular pH associated with the secretion of catecholamines induced by barium in perfused bovine adrenal medulla.

1. The possible modifications of extracellular pH produced during buffer-free 5 mM Ba2+ stimulation was studied in decorticated perfused bovine adrenal glands. 2. A significant and reversible drop of pH accompanied the release of catecholamines each time the tissue was exposed to a buffer-free 5 mM Ba2+ solution. 3. A progressive declination of the magnitude of this acidification associated with a gradual attenuation of the secretory response was observed consecutive to successive periods of Ba(2+)-stimulation. 4. D-600 (methoxyverapamil), in a concentration of 3 x 10(-4) M, markedly antagonized both Ba(2+)-induced secretory response and extracellular pH drop. 5. Perfusion of adrenal medulla for 4 min period with Locke solution buffered at pH 6.9, significantly and reversibly reduced the secretory response to 5 mM Ba2+ (pH 6.9) compared to a first control response obtained 35 min before at pH 7.4. 6. These results are compatible with the view that Ba(2+)-induced secretory activity is accompanied by the release of protons which could be involved in a local negative automodulatory mechanism of adrenomedullary secretion.

Acute effects of doxorubicin on chronotropic and inotropic mechanisms in guinea pig atria.

This study was designed to test the possible acute effects of doxorubicin (DOX) on isolated guinea pig atria incubated in Locke's solution. Different concentrations of DOX (10(-6) to 10(-4) M) were added to the medium 30 minutes before the concentration-response curves to noradrenaline and histamine were carried out. DOX (10(-4) M) significantly reduced spontaneous atrial rate. Atropine (10(-6) g/ml) was unable to modify this cardiodepressant effect. DOX (10(-4) M) produced a competitive beta blocking effect, shifting to the right the concentration-response curve to noradrenaline without altering the maximal chronotropic response. On the other hand, this anthracycline (10(-4) M) not only antagonized chronotropic responses to histamine, but significantly reduced the maximal effect mediated by this amine. Isolated left guinea pig atria electrically paced were used to determine the effects of DOX on positive inotropic activity promoted by noradrenaline and histamine. Similarly to what was observed in chronotropic experiments, DOX (10(-4) M) produced a competitive beta blocking action and a noncompetitive inhibition of the positive inotropic action developed by histamine. Lower concentrations of DOX failed to modify the chronotropic responses to both amines. However, after 60 minutes of incubation with DOX, 10(-5) M of this drug produced a shift to the right of the concentration-response curves to noradrenaline and histamine and depressed the maximal chronotropic response to these amines. These effects were not observed with 3 X 10(-6) M DOX. These results are compatible with the idea that a nonspecific interaction of DOX with cardiac beta and histaminergic receptors could be involved in the acute cardiotoxic mechanism produced by this anthracycline.