Browsing by Author "LLONA, I"

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    BRADYKININ MODULATES THE RELEASE OF NORADRENALINE FROM VAS-DEFERENS NERVE-TERMINALS
    (1991) LLONA, I; GALLEGUILLOS, X; BELMAR, J; HUIDOBROTORO, JP
    To assess whether bradykinin influences the release of noradrenaline from the adrenergic varicosities of the vas deferens, tissues were loaded with 3H-noradrenaline. Upon electrical depolarization bradykinin increased in a concentration-dependent fashion, the overflow of tritium from the mouse or rat vas deferens. The 3H-overflow is dependent on the external Ca2+ concentration suggesting neuronal release of 3H-noradrenaline. The present results add evidence to the hypothesis that bradykinin modulates the release of noradrenaline from peripheral sympathetic nerve terminals via the activation of a presynaptic mechanism.
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    HEPARIN-ACETYLCHOLINESTERASE INTERACTION - SPECIFIC DETACHMENT OF CLASS I-A FORMS AND BINDING OF CLASS I AND CLASS-II-A FORMS TO HEPARIN-AGAROSE
    (1986) BRANDAN, E; LLONA, I; INESTROSA, NC
    This study describes the specificity, time-course and characteristics of the solubilization of class I-A forms of AChE by heparin, from the endplate regions of rat diaphragm muscle. Heparin fractions which differed in charge size, anticoagulant activity and capacity to bind type I collagen, were probed in their ability to extract AChE. No differences were found among all the fractions tested. Affinity chromatography on heparin-agarose of class I- and class II-A forms of esterase showed that both classes were able to bind to the column with the same relative affinity. Our results establish the use of heparin, as a solubilizing agent for the class I-A. The existence of a heparin-binding domain in class I- and class II-A forms of AChE, opens the possibility, that heparan sulfate proteoglycans could be involved in the anchorage of both types of esterase to synaptic regions. Finally, our results suggest that class I and class II-A do not correspond to intrinsically distinct molecules, but rather to identical molecules engaged in different interactions in the tissue.
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    IDENTIFICATION OF PRESYNAPTIC AND POSTSYNAPTIC BRADYKININ RECEPTOR-SITES IN THE VAS-DEFERENS - EVIDENCE FOR DIFFERENT STRUCTURAL PREREQUISITES
    (1987) LLONA, I; VAVREK, R; STEWART, J; HUIDOBROTORO, JP
    The effect of bradykinin on the neuroeffector junction of the isolated rat vas deferens was studied in tissues stimulated transmurally at a frequency of 0.15 Hz. Bradykinin caused two distinct and independent actions: it potentiated the magnitude of the muscular response to the electrically driven twitches and, in addition, contracted the smooth muscle generating an increased muscular tone. The former action is referred to as the neurogenic or presynaptic effect, whereas the latter effect is called the musculotropic or postjunctional action. The neurogenic effect was abolished by tetrodotoxin or tissue denervation either by cold storage or chemical sympathectomy after 6-hydroxydopamine administration. However, these procedures did not significantly modify the musculotropic potency of bradykinin. Both actions of the peptide are receptor-mediated, as minor structural modifications in the amino acid sequence caused significant changes in biological potency. In addition, the peptide analog, [Thi5,8-D-Phe7]-bradykinin, behaved as an agonist at the presynaptic site but as an antagonist at the muscular site. The most potent peptide analog to produce the neurogenic effect was Met-Lys-bradykinin followed by Lys-bradykinin and [Tyr8]-bradykinin. In contrast, the potency of these peptide analogs acting at the postsynatpic site was about the same. des Arg9 bradykinin and des Arg9-[Leu8]-bradykinin were inactive at the pre- and postjunctional site. The neurogenic action of bradykinin was not mimicked by angiotensin II, neurotensin, substance P or vasopressin. In terms of the musculotropic effect, angiotensin II was as potent as bradykinin and substance P had 1/25 the potency neurotensin and vasopressin were inactive. It is concluded that the rat vas deferens contains bradykinin receptors on the nerve endings and on the smooth muscle membrane. The structural prerequistes for the activation of these receptor sites appear to be slightly different.