The inhibitory role of nitric oxide in the control of porcine and human sphincter of Oddi activity

Abstract

Background-The possible role of nitric oxide in the regulation of the sphincter of Oddi is not known in species with a resistor-like sphincter of Oddi such as humans and pigs. Methods-Sphincter of Oddi perfusion manometry and simultaneous electromyography (EMG) were recorded transduodenally in eight anaesthetised pigs. Acetylcholine (4 µg/kg) was given intraarterially, with or without sodium nitroprusside (10-100 µg/kg), an exogenous nitric oxide donor. For in vitro studies the sphincter was removed from the eight pigs and from six patients undergoing pancreaticoduodenectomy, cut into rings, and the amplitude of contraction was measured in an ex vivo bath. Each ring was stimulated with acetylcholine (100 µM) and KCl (125 mM). The stimulation was repeated after incubation with L-NAME (a stereospecific competitive inhibitor of nitric oxide synthase), with L-NAME plus L-arginine (a substrate for nitric oxide synthase), and with sodium nitroprusside. The sphincter rings were then submersed in liquid nitrogen and stored. Immunohistochemical analysis was used to localise nitric oxide synthase in the pig and human sphincter specimens. Results-In vivo EMG revealed 2-3 phasic bursts per minute with the basal pressure variation 6-40 mm Hg. Acetylcholine induced a large electrical burst and the pressure increased by (mean (SE)) 20 (10) mm Hg (p <0.01) for 17 (4) seconds. After sodium nitroprusside (10 µg/kg) acetylcholine did not induce pressure changes and electrical activity was almost abolished. In vitro, L-NAME increased the KCl induced sphincter contraction in both pig and human specimens (p<0.01). In human, but not in pig, specimens L-NAME increased the amplitude of acetylcholine induced contraction (p<0.01). L-Arginine partly reversed the eVect of L-NAME in both pig and human specimens. Sodium nitroprusside decreased the acetylcholine and KCl induced contractions in both pig and human specimens. Immunohistochemical studies localised nitric oxide synthase to rich plexi of nerve fibres in the mucosa and the muscle in both pig and human sphincter of Oddi. Conclusions-The sphincter of Oddi in both pigs and humans has endogenous nitric oxide synthase activity and immunoreactivity. Inhibition of endogenous nitric oxide production enhances contractility while exogenous nitric oxide decreases sphincter contractility and electrical activity. (Gut 1997; 41: 375-380) Keywords: NO; nitric oxide synthase; nitroprusside; sphincter of Oddi; pig; human The sphincter of Oddi (SO) regulates bile flow into the duodenum by behaving either as a pump (category I) or as a passive resistor (category II), depending upon the species of animal.1 2 The physiological control of the SO is complex and includes both neural and humoral factors. In recent years much attention has been focused on the role of nitric oxide (NO), a potent smooth muscle relaxant produced by enteric nerves, in the regulation of gastrointestinal smooth muscle function. NO is known to cause relaxation of the SO in category I species (with a pump-like sphincter) s...

Distribution of nitric oxide synthase and vasoactive intestinal polypeptide immunoreactivity in the sphincter of Oddi and duodenum of the possum

“…Excitatory innervation is primarily cholinergic, whereas inhibitory innervation is predominantly non-adrenergic and non-cholinergic (NANC; Helm et al 1989;Toouli and Baker 1991;Baker et al 1993). Nitric oxide (NO) is an important NANC inhibitory neurotransmitter in the SO of several species (Allescher et al 1993;Lonovics et al 1994;Tanobe et al 1995;Thune et al 1995), including the Australian possum (Baker et al 1993) and human (Sand et al 1997). NO has also been implicated in NANC inhibitory innervation in the duodenum in several species (Bayguinov et al 1992;Elbrond et al 1994;Konomi et al 2000).…”

“…In the SO of the Australian possum and in several species including the human, NO synthase (NOS)-containing nerves have been identified in neural plexuses by using either NOS immunohistochemistry or β-nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) staining (Baker et al 1993;De Giorgio et al 1994;Wells and Mawe 1993;Sand et al 1997). The distribution of NOS-immunoreactive (NOS-IR) neurons within different regions of the SO and duodenum has not been fully described and reports of NOS-containing nerves in the various layers of the SO and duodenum, unlike that of the ileum, are limited (Belai et al 1992;Ekblad et al 1994;Furness et al 1994).…”

Gastrointestinal Function Regulation by Nitrergic Efferent Nerves

“…NO is a major transmitter of NANC neurogenic relaxation of the sphincter of Oddi in the guinea pig Pauletzki et al, 1993), opossum (Allescher et al, 1993), Australian possum (Baker et al, 1993), rabbit (Lonovics et al, 1994), dog (Tanobe et al, 1995), pig, and human (Sand et al, 1997). Nitrergic nerve stimulation induced relaxation in association with an increase in the tissue cyclic GMP content in the rabbit sphincter of Oddi (Szilvassy et al, 1998).…”

Comparative relaxant effects of YC-1 and DEA/NO on the sheep sphincter of Oddi

“…Topical administration of a NO donor induces SO relaxation in humans, and intrasphincteric injection of sodium nitroprusside (SNP) decreases sphincter contractility in pig SO [20,21] . SNP and DEA/NO are NO donors, but SNP and recently developed DEA/NO do not share the same mechanism for NO release.…”