title: Endothelin-1 stimulates NO production and inhibits cAMP accumulation in rat inner medullary collecting duct through independent pathways.
abstract: Endothelin-1 (ET-1) inhibition of vasopressin (AVP)-stimulated cAMP accumulation in the collecting duct has been hypothesized to be mediated, at least in part, by nitric oxide (NO). To examine this, the effect of ET-1 on NO production by acutely isolated rat inner medullary collecting duct (IMCD) cell suspensions and the role of NO in mediating ET-1 effects on AVP-stimulated cAMP accumulation were studied. ET-1 dose dependently (first evident at 100 pM ET-1) increased IMCD NO production as determined by DAF-FM fluorescence. ET(B) receptor (BQ-788), but not ET(A) receptor (BQ-123), antagonism blocked this effect. Nonspecific NO synthase (NOS) inhibitors [N(G)-nitro-L-arginine methyl ester (L-NAME) or N(G)-monomethyl-L-arginine] or NOS-1 inhibitors (SMTC or VNIO) inhibited the ET-1 response, whereas NOS-2 or NOS-3 inhibitors (L-NAA or 1400W) were ineffective. ET-1 also increased cGMP accumulation. ET-1 caused a 35% reduction in AVP-stimulated cAMP levels; however, this response was not affected by L-NAME or SMTC. The addition of L-arginine, NADPH, tetrahydrobiopterin, or tempol (to reduce superoxide-dependent conversion of NO to peroxynitrate) did not affect the response. NO donors (SNAP or spermine NONOate), at concentrations that stimulated DAF-FM fluorescence and increased cGMP levels, did not alter AVP-stimulated cAMP accumulation in the IMCD cell suspensions. In conclusion, ET-1 stimulates IMCD NO production through activation of the ET(B) receptor and NOS-1. However, neither ET-1-mediated NO production nor NO donors inhibit AVP-stimulated cAMP accumulation, indicating that NO does not mediate ET-1 inhibition of cAMP production by the IMCD.
authors.affiliation: Division of Nephrology, Univ. of Utah Health Sciences Center, 1900 East, 30 North, Salt Lake City, UT 84132, USA.
authors.forename: Peter K
authors.initials: PK
authors.lastname: Stricklett
authors.forename: Alisa K
authors.initials: AK
authors.lastname: Hughes
authors.forename: Donald E
authors.initials: DE
authors.lastname: Kohan
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D065130:Endothelin A Receptor Antagonists; D065131:Endothelin B Receptor Antagonists; D019332:Endothelin-1 / Q000494:pharmacology*; D007679:Kidney Medulla / Q000378:metabolism*; D007685:Kidney Tubules, Collecting / Q000378:metabolism*; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis* / Q000502:physiology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology; D052248:Nitric Oxide Synthase Type I; D051381:Rats; D017207:Rats, Sprague-Dawley; D044022:Receptor, Endothelin A / Q000502:physiology; D044023:Receptor, Endothelin B / Q000502:physiology
chemical_list: D065130:Endothelin A Receptor Antagonists; D065131:Endothelin B Receptor Antagonists; D019332:Endothelin-1; D020030:Nitric Oxide Donors; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D001127:Arginine Vasopressin; D009569:Nitric Oxide; D000242:Cyclic AMP; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; C496322:Nos1 protein, rat