The effects of neosurugatoxin on evoked catecholamine secretion from bovine adrenal chromaffin cells

Abstract

1 The effect of neosurugatoxin (NSTX), a toxin from the Japanese ivory mollusc (Babylonia japonica), on the nicotinic response of bovine adrenal chromaffin cells was examined. 2 NSTX inhibited acetylcholine-and nicotine-induced catecholamine secretion from the cultured cells with an ICO against 5 JLM nicotine of 30 nM. 3 This inhibitory effect was reversible and independent of the presence of agonist. 4 NSTX had no effect on the catecholamine release from cultured cells evoked by 50 mM K+, or 1 J1M histamine. 5 NSTX had no effect on the stimulation of phosphatidylinositol metabolism evoked by 100 tiM muscarine.6 These results suggest NSTX may be useful as a nicotinic receptor probe in tissues such as the adrenal and sympathetic ganglia where a-bungarotoxin is ineffective. IntroductionIn studies of receptor-ionophore function in adrenal chromaffin cells, there is currently a need for a better probe for the nicotinic receptor. Hexamethonium is a weak, non-competitive inhibitor of the nicotinic response (Kilpatrick et al., 1981), while x-bungarotoxin binds with high affinity to the chromaffin cells but does not inhibit the nicotinic response (Kumakura et al., 1980;Quik & Trifaro, 1982).Neosurugatoxin (NSTX) is a novel marine toxin recently isolated from the Japanese ivory mollusc, Babyloniajaponica (Kosuge et al., 1981). The structure ofNSTX is shown in Figure 1 , 1974;Hayashi & Yamada 1975; Hayashi et al., 1984).The high affinity of the toxin for ganglionic nicotinic receptors over ganglionic muscarinic receptors has been demonstrated in the isolated superior cervical ganglion of the rat. Extracts of the Japanese ivory mollusc were shown to depress reversibly orthodromic transmission and antagonize the depolarizing action of carbachol on nicotinic receptors, while failing to reduce the depolarizing effects of muscarine (Brown et al., 1976 (Hayashi et al., 1984;Yamada et al., 1985;Rapier et al., 1985).In the present study, the action of NSTX on nicotine-induced catecholamine secretion and muscarine-induced phosphatidyl inositol (PI) metabolism h to allow incorporation of the label.In the standard protocol to test the ability of NSTX to modify muscarine-induced PI metabolism, the dishes were removed from the incubator and the loading medium removed. Each well then received two consecutive 5 min washes at 37°C with incubation buffer of the following composition (mM): NaCI 149, KCl 2.6, K2HPO4 2.15, KH2PO4 0.85, MgSO4 1.18, LiCI 5, glucose 10, pH 7.4. PI metabolism was then stimulated for 30 min at 37'C by 100 pM muscarine in the same incubation buffer. The effects of NSTX and atropine were determined by including the drug in both the second wash and the stimulation period. The incubation was terminated by replacing the buffer with 1 ml ice cold 15% trichloroacetic acid (TCA) and extracting the cells for I h. This TCA was collected into glass tubes, and the cells were rinsed with a further 0.5 ml of TCA which was collected after 5 min.The extraction and analysis of inositol phosphates was performed using a mo...

Biomedical Potential of Marine Natural Products

“…It is generally accepted that there are two subclasses of nACh receptors in nervous tissue, the socalled high-and low-affinity agonist receptors (Billiar et al, 1988). Neosurugatoxin binds with high selectivity at the high-affinity agonist site, as indicated by the observation that it did not inhibit a-bungarotoxin binding, a known antagonist at the low-affinity site (Billiar et al, 1988;Bourke et al, 1988). The selectivity of neosurugatoxin for specific receptors in nervous tissue illustrated the pharmacological distinction between ganglionic nACh receptors and those at the neuro-…”

The effect of neosurugatoxin on the release of neurohypophysial hormones by nicotine, hypotension and an osmotic stimulus in the rat

“…has an anti-nicotinic action on the guinea-pig ileum about 100 times as potent as that reported for surugatoxin with a pA2 of 9.07 compared with 5.46 for hexamethonium (Kosuge et al, 1982;Hayashi et al, 1983;1984). It also inhibits the secretion of catecholamines from cultured bovine adrenal medullary cells in response to nicotine (Bourke et al, 1988) and carbachol (Wada et al, 1989).…”

Inhibition of nicotinic responses of bovine adrenal chromaffin cells by the protein kinase C inhibitor, Ro 31–8220

“…Although this effect is unrelated to its ability to inhibit PK-C, it is clearly a structurally specific effect since it is not shared by the related compounds bisindolylmaleimides I ore V ( Figures 5-7 clonidine, phentolamine, yohimbine, propranolol, oxymetazoline and neosurugatoxin (Mizobe et al, 1979;Marley et al, 1986;Powis & Baker, 1986;Orts et al, 1987;Bourke et al, 1988;Wan et al, 1988;Cheung et al, 1993 Toullec et al, 1991;Davis et al, 1992a,b;Bit et al, 1993) and many of these are available for further characterization of its structure-activity profile against nicotinic receptors. It will also be of interest to determine the selectivity of Ro 31-8220 for the chromaffin cell form of nicotinic receptor compared with the neuromuscular junction, autonomic ganglia and CNS types of nicotinic receptor.…”