Endothelin-1, superoxide and adeninediphosphate ribose cyclase in shark vascular smooth muscle.
In vascular smooth muscle (VSM) of Squalus acanthias, endothelin-1 (ET-1) signals via the ET(B) receptor. In both shark and mammalian VSM, ET-1 induces a rise in cytosolic Ca(2+) concentration ([Ca(2+)](i)) via activation of the inositol trisphosphate (IP(3)) receptor (IP(3)R) and subsequent release of Ca(2+) from the sarcoplasmic reticulum (SR). IP(3)R-mediated release of SR Ca(2+) causes calcium-induced calcium release (CICR) via the ryanodine receptor (RyR), which can be sensitized by cyclic adeninediphosphate ribose (cADPR). cADPR is synthesized from NAD(+) by a membrane-bound bifunctional enzyme, ADPR cyclase. We have previously shown that the antagonists of the RyR, Ruthenium Red, high concentrations of ryanodine and 8-Br cADPR, diminish the [Ca(2+)](i) response to ET-1 in shark VSM. To investigate how ET-1 might influence the activity of the ADPR cyclase, we employed inhibitors of the cyclase. To explore the possibility that ET-1-induced production of superoxide (O(2)*-) might activate the cyclase, we used an inhibitor of NAD(P)H oxidase (NOX), DPI and a scavenger of O(2)*-, TEMPOL. Anterior mesenteric artery VSM was loaded with fura-2AM to measure [Ca(2+)](i). In Ca(2+)-free shark Ringers, ET-1 increased [Ca(2+)](i) by 104+/-8 nmol l(-1). The VSM ADPR cyclase inhibitors, nicotinamide and Zn(2+), diminished the response by 62% and 72%, respectively. Both DPI and TEMPOL reduced the response by 63%. The combination of the IP(3)R antagonists, 2-APB or TMB-8, with DPI or TEMPOL further reduced the response by 83%. We show for the first time that in shark VSM, inhibition of the ADPR cyclase reduces the [Ca(2+)](i) response to ET-1 and that superoxide may be involved in the activation of the cyclase.
Fellner
Susan K
SK
Mount Desert Island Biological Laboratory, Salisbury, Maine 04672, USA. sfellner@med.unc.edu
Parker
Laurel
L
D036541:ADP-ribosyl Cyclase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D000818:Animals; D001267:Atlantic Ocean; D001896:Boron Compounds / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002395:Catecholamines / Q000494:pharmacology; D003497:Cyclic N-Oxides / Q000494:pharmacology; D019332:Endothelin-1 / Q000378:metabolism*; D016257:Fura-2 / Q000031:analogs & derivatives*; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D048288:Imidazolines / Q000494:pharmacology; D053496:Inositol 1,4,5-Trisphosphate Receptors; D009131:Muscle, Smooth, Vascular / Q000201:enzymology* / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors; D019255:NADPH Oxidases; D009536:Niacinamide / Q000494:pharmacology; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D013113:Spin Labels; D048251:Squalus acanthias / Q000378:metabolism* / Q000502:physiology; D013481:Superoxides / Q000378:metabolism*; D015032:Zinc / Q000494:pharmacology
D001896:Boron Compounds; D015220:Calcium Channels; D002395:Catecholamines; D003497:Cyclic N-Oxides; D019332:Endothelin-1; D048288:Imidazolines; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D019837:Ryanodine Receptor Calcium Release Channel; D013113:Spin Labels; C049925:fura-2-am; D013481:Superoxides; D009536:Niacinamide; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; C011775:(3,4-dihydroxyphenylamino)-2-imidazoline; C109986:2-aminoethoxydiphenyl borate; D009247:NADH, NADPH Oxidoreductases; D019255:NADPH Oxidases; D036541:ADP-ribosyl Cyclase; D015032:Zinc; D002118:Calcium; D016257:Fura-2; C001803:tempol