Cyclic nucleotide-mediated effects of ANF and VIP on flounder intestinal ion transport.
The purpose of this study was to compare the effects of atriopeptin III (AP-III), vasoactive intestinal peptide (VIP), and ionomycin on Na and Cl influx and to correlate changes in transport with effects on intracellular adenosine 3',5'-cyclic monophosphate (cAMP) and guanosine 5'-cyclic monophosphate (cGMP) content of the tissue. In addition, the question of whether AP-III inhibits ion transport directly by acting on enterocyte receptors for AP-III or indirectly by stimulation of enteric nerves in the submucosa was also addressed. The results showed that AP-III, ionomycin, and bumetanide all inhibited the initial rate of Na and Cl influx, suggesting that they directly block Na-K-2Cl cotransport activity. VIP had no effect on unidirectional influx of Na and Cl. AP-III caused a fourfold increase in intracellular [cGMP] without any significant effect on [cAMP]. VIP stimulated [cAMP] by fourfold but had no effect on [cAMP]. Ionomycin had no effect on either [cAMP] or [cGMP]. Inhibition of transport by AP-III could not be blocked by tetrodotoxin (TTX), indicating that enteric nerves in the submucosa are not directly involved in mediating the effects of AP-III on epithelial ion transport. The observation that two classes of neuronal depolarizing agents (veratrine and scorpion venom) cause TTX-sensitive inhibition of basal ion transport establishes that NaCl absorption in flounder intestine is subject to regulation by enteric nerves located in the submucosa.
O'grady
S M
SM
Department of Veterinary Biology, University of Minnesota, St. Paul 55108.
D000818:Animals; D000838:Anions; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D001692:Biological Transport / Q000187:drug effects; D002034:Bumetanide / Q000494:pharmacology; D002414:Cations, Monovalent; D002712:Chlorides / Q000378:metabolism*; D000242:Cyclic AMP / Q000502:physiology*; D006152:Cyclic GMP / Q000502:physiology*; D004553:Electric Conductivity; D004987:Ethers / Q000494:pharmacology; D005412:Flatfishes / Q000378:metabolism*; D005432:Flounder / Q000378:metabolism*; D007408:Intestinal Absorption / Q000187:drug effects*; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects / Q000294:innervation; D015759:Ionomycin; D007700:Kinetics; D012604:Scorpion Venoms / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism*; D013779:Tetrodotoxin / Q000494:pharmacology; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*; D014702:Veratrine / Q000494:pharmacology
D000838:Anions; D002414:Cations, Monovalent; D002712:Chlorides; D004987:Ethers; D012604:Scorpion Venoms; D002034:Bumetanide; D014660:Vasoactive Intestinal Peptide; D013779:Tetrodotoxin; D015759:Ionomycin; D009320:Atrial Natriuretic Factor; D012964:Sodium; D000242:Cyclic AMP; D014702:Veratrine; D006152:Cyclic GMP