Neurogenic chloride secretion induced by scorpion venom and veratrine in rabbit colon.
In earlier reconstitution experiments the venom of the scorpion Leiurus quinquestriatus, LQV, was shown to block Ca(2+)-activated high-conductance K+ channels from the basolateral cell membrane of rabbit colonocytes (Turnheim K, Costantin J, Chan S, Schultz SG (1989) J Membrane Biol 112:247-254). These LQV-sensitive K+ channels do not seem to be involved in active Na+ transport across rabbit colon, as absorptive Na+ fluxes were not significantly affected by serosal addition of LQV to isolated epithelia of rabbit descending colon. While Na+ absorption was not changed, LQV and veratrine caused electrogenic Cl- secretion in this tissue by a neural (tetrodotoxin sensitive) mechanism. The secretory effect of LQV was partly inhibited by atropine, suggesting the involvement of m-cholinoceptors, and by a VIP-antagonist. In contrast to the neurogenic secretion in the small intestine of guinea pig, rat and cat, 5-hydroxytryptamine (5-HT) does not seem to be involved in neurogenic secretion in rabbit colon, as 1) several 5-HT receptor antagonists did not inhibit the LQV effect with the exception of high concentrations of tropisetron, 2) exogenous 5-HT had no secretory effect, and 3) there was no significant release of 5-HT from the tissue during neurogenic secretion. The inhibitory effect of tropisetron on intestinal Cl- secretion seems to be unrelated to its property as a 5-HT3 receptor antagonist.
Plass
H
H
Pharmakologisches Institut, Universität Wien, Vienna, Austria.
Wachter
C
C
Turnheim
K
K
D000818:Animals; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism*; D003106:Colon / Q000187:drug effects* / Q000294:innervation / Q000378:metabolism; D004848:Epithelium / Q000187:drug effects / Q000294:innervation / Q000378:metabolism; D066298:In Vitro Techniques; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D011817:Rabbits; D012604:Scorpion Venoms / Q000494:pharmacology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D013779:Tetrodotoxin / Q000633:toxicity; D014702:Veratrine / Q000494:pharmacology*
D015220:Calcium Channels; D002712:Chlorides; D015221:Potassium Channels; D012604:Scorpion Venoms; D012702:Serotonin Antagonists; D013779:Tetrodotoxin; D012964:Sodium; D014702:Veratrine