Endothelin and a Ca2+ ionophore raise cyclic GMP levels in a neuronal cell line via formation of nitric oxide.
1. The vasoconstrictor peptide endothelin-1 caused a fast, transient rise in guanosine 3':5'-cyclic monophosphate (cyclic GMP) levels in a neuronal cell line (mouse neuroblastoma x rat glioma hybrid cells 108CC15). The mechanism of activation of guanylate cyclase by endothelin-1 was investigated. The endothelin-1-induced rise depended on the release of internal Ca2+. 2. The stimulation of cyclic GMP synthesis induced by endothelin-1 was suppressed after preincubating the cells in medium containing haemoglobin (IC50 3 microM). Similarly, pretreatment of the cells with the L-arginine analogues, L-canavanine (IC50 60 microM) or NG-monomethyl-L-arginine (IC50 2.5 microM), inhibited the cyclic GMP response to endothelin-1. Therefore, endothelin-1 activates guanylate cyclase most probably via formation of nitric oxide, which is released from L-arginine. 3. The Ca2+ ionophore ionomycin induced a transient rise in cyclic GMP levels, which was also suppressed by preincubation in the presence of either haemoglobin or the L-arginine analogues L-canavanine or NG-monomethyl-L-arginine. Therefore, we conclude that ionomycin can activate guanylate cyclase by a mechanism involving nitric oxide formation, similar to that induced by endothelin-1. 4. The alkaloid veratridine, which activates Na+ channels and also causes influx of Ca2+ induced a transient rise of cyclic GMP levels in the neuronal cell line. This stimulation was blocked by pretreating the cells with L-canavanine, NG-monomethyl-L-arginine or haemoglobin. 5. Loading the cells with the Ca2+ chelator BAPTA suppresed the cyclic GMP response to application of endothelin-1, ionomycin, or veratridine. Thus, in the neuronal cell line a rise in cytosolic Ca2 + activity seems to be sufficient to stimulate the nitric oxide forming enzyme which synthesizes the activator of soluble guanylate cyclase.
Reiser
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Physiologisch-Chemisches Institut der Universität Tübingen, F.R.G.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D006152:Cyclic GMP / Q000378:metabolism*; D016232:Endothelins / Q000494:pharmacology*; D006822:Hybrid Cells / Q000187:drug effects / Q000378:metabolism; D015759:Ionomycin / Q000494:pharmacology; D008751:Methylene Blue / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D014701:Veratridine / Q000494:pharmacology
D016232:Endothelins; D009569:Nitric Oxide; D015759:Ionomycin; D014701:Veratridine; D006152:Cyclic GMP; D002118:Calcium; D008751:Methylene Blue