title: Effects of alpha- and beta-adrenergic agonists on Trypanosoma cruzi interaction with host cells.
abstract: We studied the effects of adrenergic agonists on the capacity of blood trypomastigote forms of Trypanosoma cruzi to associate with (i.e., bind and/or penetrate) host cells in vitro. The extent of T. cruzi association with mouse macrophages in the presence of the beta-adrenergic agonist L-isoproterenol was significantly decreased with respect to mock-treated controls. Similar results were obtained when the parasite was pretreated with L-isoproterenol and was then allowed to interact with untreated macrophages. In contrast, pretreatment of trypomastigotes with either L-phenylephrine or methoxamine-alpha-adrenergic agonists--enhanced their reactivity with macrophages. Interaction with a nonphagocytic host cell was also decreased and increased by parasite pretreatment with beta- and alpha-adrenergic agonists, respectively. The L-isoproterenol and L-phenylephrine effects were no longer detectable 2 and 3 hr after their removal, respectively, and were therefore reversible. Atenolol, a specific beta 1 adrenoreceptor blocker inhibited the L-isoproterenol effect, whereas butoxamine, a specific beta 2 blocker, did not. Thus, beta 1-like but not beta 2-like binding sites appeared to be expressed on T. cruzi. Both prazosin and yohimbine, preferential alpha 1- and alpha 2-receptor blockers, respectively, abolished the L-phenylephrine effect. The opposite effects of alpha- and beta-adrenergic agonists suggested that the infectivity of T. cruzi may be regulated by activation of surface components comparable to the adreno-receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D005434:Flow Cytometry; D006790:Host-Parasite Interactions / Q000187:drug effects*; D007545:Isoproterenol / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000469:parasitology; D008729:Methoxamine / Q000494:pharmacology*; D051379:Mice; D008808:Mice, Inbred CBA; D008815:Mice, Inbred Strains; D010656:Phenylephrine / Q000494:pharmacology*; D013997:Time Factors; D014349:Trypanosoma cruzi / Q000187:drug effects / Q000472:pathogenicity*
chemical_list: D000317:Adrenergic alpha-Antagonists; D000319:Adrenergic beta-Antagonists; D010656:Phenylephrine; D008729:Methoxamine; D007545:Isoproterenol