Figure 6 Pressor effect of infusions of Ligaria cuneifolia. Change of mean arterial pressure (MAP) induced by infusions of L. cuneifolia (1.25, 2.5 and 5.0% P/V) by intravenous injection in Wistar rats (each point is the mean ± SEM of four experiments). Host tree: □ A. cavens, O S. polygamus, D G. decorticans (*p<0.05).
the extract suggests that the effect is of adrenergic origin (Lefkowitz et al., 1991). Cholinergic blockade brought about by atropin evidence that both hypotension and bradicardia are related to muscarinic receptors (Lefkowitz et al., 1991).
In the Argentine mistletoe specimen parasiting A. caven, an a-adrenergic compound with pressor effect is also present. Unlike the S. polygamus sample, the hypotensive effect may be observed after adrenergic blockade, but the nature of the hypotensive agent is unknown. High concentrations of the extract also produce a drop in heart rate. L.cuneifolia collected from G. decorticans only exerts a minor pressor effect and no changes in heart rate are observed.
On the basis of these results, it may be posited that the host tree is capable of modulating the profile of vasoactive components produced by the mistletoe.
A wide range of biological activities has been reported for various mistletoes including antiviral, antitumoural, immunomodulating and inflammation modifying effects. V. album extracts specifically have been popular in Europe for seven decades as an unconventional approach to cancer treatment (Bloksma et al., 1982, Hajto, 1986, Jurin et al., 1993). Tumour-reducing or modulating components have been identified as lectins, viscotoxins, proteins, peptides, oligosaccharides, alkaloids, polyphenolic compounds and flavonoids (Khwaja et al., 1986; Hostanska et al., 1995; Kuttan et al., 1997; Stein and Berg, 1997; Beuth et al., 1996; Büssing et al., 1996; Gabius et al., 1992; Zee Cheng, 1997). Anti-cancer activity may not only be due to inhibition of cellular proliferation but also to cytokine induction and immunoadjuvant effects (Hostanska et al., 1995; Männel et al., 1991; Müller and Anderer, 1990).
To study the possible immunomodulating effect exerted by L. cuneifolia extracts, parameters of cell proliferation and function have been evaluated. When variable concentrations of plant extract are added to normal murine splenocytes, their growth
Table 2 Effect of L. cuneifolia on the proliferation of murine splenocytes.
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