Sergio Pablo Sardi

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.

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

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.

Characterization of α1‐adrenoceptor subtypes mediating vasoconstriction in human umbilical vein

The present study attempted to characterize pharmacologically the subtypes of α‐adrenoceptors mediating contractions in human umbilical vein (HUV). HUV rings were mounted in isolated organ baths and cumulative concentration‐response curves were constructed for the α‐adrenoceptor agonists phenylephrine and adrenaline. Adrenaline was more potent than phenylephrine (pD2=7.29 and 6.04 respectively). Isoproterenol exhibited no agonism on KCl pre‐contracted HUV rings. Propranolol (1 μM) and rauwolscine (0.1 μM) did not affect the concentration‐response curves to adrenaline. These results demonstrate the lack of involvement of functional β‐ or α2‐adrenoceptors in adrenaline‐induced vasoconstriction. The non subtype selective α1‐adrenoceptor antagonist prazosin was evaluated on phenylephrine and adrenaline concentration‐response curves. The effects of the competitive α1A and α1D‐adrenoceptor antagonists, 5‐methyl urapidil and BMY 7378 and the irreversible α1B selective compound chloroethylclonidine (CEC) were also evaluated on adrenaline concentration‐response curves. The potencies of prazosin against responses mediated by adrenaline (pA2=10.87) and phenylephrine (pA2=10.70) indicate the involvement of prazosin‐sensitive functional α1‐adrenoceptor subtype in vasoconstriction of the HUV. The potencies of 5‐methyl urapidil (pA2=6.70) and BMY 7378 (pA2=7.34) were not consistent with the activation of an α1A‐ or α1D‐adrenoceptor population. Exposure to a relatively low CEC concentration (3 μM) abolished the maximum response to adrenaline suggesting that this response was mediated by an α1B‐adrenoceptor subtype. We conclude that HUV express a prazosin‐sensitive functional α1‐adrenoceptor resembling the α1B‐subtype according with the low pA2 values for both 5‐methyl urapidil and BMY 7378 and the high sensitivity to CEC.

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.