Evidence for the absorption and synthesis of 5-hydroxytryptamine in perfused muscle and intestinal tissue and whole worms of adult Ascaris suum

Abstract

The metabolites of 5-hydroxytryptamine (5-HT, serotonin) namely, L-tryptophan, 5-hydroxytryptophan, 5-hydroxyindole acetic acid and 5-hydroxytryptophol were measured in perfused tissue and whole worms from adult female Ascaris suum using reversed-phase liquid chromatography with electrochemical detection. The intracellular levels of each metabolite were quantitated in response to several physiological effectors but only L-tryptophan (TRP) caused dose-dependent changes in these metabolites. Serotonin itself could also be absorbed by perfused A. suum muscle and intestinal tissue. When live A. suum were tied at the anterior and posterior regions to restrict TRP absorption by the intestine, TRP was absorbed through the cuticle and converted into 5-HT by the muscle tissue. In united live parasites TRP absorption was observed in both muscle and intestinal tissue. Collectively, the data indicated that 5-HT may be either absorbed directly or synthesized de novo from absorbed TRP in the isolated tissue of A. suum. The 5-HT, in the adult female A. suum, can be synthesized de novo from TRP, or 5-HT can be absorbed from the environment both through the cuticle and by the intestine of living parasites. Data also indicated that there was preferential sequestering of 5-HT and the metabolites of 5-HT in the anterior tissues of the worms.

Immunocytochemical demonstration of peptidergic and serotoninergic components in the enteric nervous system of the roundworm,Ascaris suum(Nematoda, Ascaroidea)

“…Note the extensive fine branched nerve processes in this region of the enteric nervous system. be synthesized by intestinal tissue and that serotonin receptors are present on membrane preparations from the intestine and ordinary muscle tissue (Chaudhuri, Martin & Donahue, 1988;Chaudhuri & Donahue, 1989;Williams et al 1992). The serotonin receptor is linked to a cyclic AMP system in Ascaris and differs both pharmacologically and biochemically from its mammalian counterparts.…”

Neuronal localization of serotonin inAscaris suum

“…The cellular basis of the serotonin effects on feeding, locomotion and defecation is not yet clear. The possibility that exogenous 5-HT may also play a role is raised by the demonstration that 5-HT can cross the cuticle (Chaudhuri et al, 1988a). Further studies on the cellular location and kinetic properties of the 5-HT biosynthetic and degradative enzymes and of transmernhrane transporters in Ascaris are needed.…”

Metabolism and inactivation of neurotransmitters in nematodes

“…5-Hydroxytryptamine (serotonin, 5-HT) was found in Dipetalonema viteae and Acantocheilonema viteae but not in Dipetalonema dessetae, Molinema dessetae or Litomosoides (Jacquot et al 1986;Barreteau et al 1991). In addition to de novo synthesis by tissues of A. suum, 5-HT can be absorbed from the host via the gut (Chaudhuri, Martin & Donahue, 1988) and can possibly be synthesised by gut bacterial flora (Shahkolahi & Donahue, 1993). When these observations are combined with the aforementioned analytical problems, any interpretation of amine levels in helminth parasites is speculative at best.…”

“…Evidence for the oxidative deamination of biogenic amines in nematodes comes from analytical studies that have detected MAO metabolites in tissue extracts and from biochemical studies on MAO-like activity in some, but not all, nematodes studied. 5-Hydroxyindoleacetic acid (HIAA) is a major end-product of the oxidative deamination pathway ( Fig.l) and has been chromatographically identified in S. cervi (Agarwal et al 1990), Ascaridia galli (Smart, 1988a, b), Ascaris suum (Chaudhuri, Martin & Donahue, 1988), Trichostrongylus colubriformis (Frandsen & Bone, 1987) and Nippostrongylus brasiliensis (Barreteau et al 1991;Grosclaude et al 1994) (Barreteau et al 1986) nor was MAO activity detected histochemically in Prionchulus punctatus, Panagrellus redivivus, Aphelencus avenae and C. elegans or biochemically in P. redivivus and A. avenae (Wright & Awan, 1978). MAO activity has been found in Ascaris lumbricoides (Mishra, Sen & Ghatak, 1978), N. brasiliensis (Agarwal et al 1985), A. galli (Mishra et al 1983) and S. cervi (Agarwal et al 1990).…”