title: A thromboxane A(2) system in the Atlantic stingray, Dasyatis sabina.
abstract: Thromboxane B(2)(TXB(2)) is the stable metabolite of thromboxane A(2)(TXA(2)) and thromboxane B(2)-like immunoreactivity (iTXB(2)) has been identified in the plasma of the Atlantic stingray, Dasyatis sabina (0.57+/-0.03 ng/ml). Plasma levels of iTXB(2) increase if the blood is allowed to clot (3.0+/-0.27 ng/ml). When clotting occurs in the presence of indomethacin, this increase is partially inhibited (1.5+/-0.17 ng/ml), indicating the presence of a cyclooxygenase activity. Radioligand binding analysis using the TXA(2) analog [125I]BOP in isolated kidney membranes revealed a receptor of K(d)=2.88+/-0.51 nM and B(max)=25.6+/-5.9 fmol/mg protein. [125I]BOP binding was displaced by the TXA(2) receptor (TP receptor) agonists U46619 (IC(50)=106.4+/-15.7 nM) and U44069 (IC(50)=88.7+/-13.0 nM), and the antagonist SQ29548 (IC(50)=51.0+/-12.9 nM). Binding was also displaced stereoselectively by the antagonists (-)L657925 (IC(50)=18.9+/-3.8 nM) and (+)L657926 (IC(50)=2025+/-280 nM). Tissue bath studies revealed that U46619, a stable TXA(2) mimetic, elicited concentration-dependent contractions in the ventral aorta which were inhibited in a concentration-dependent manner by the TP receptor antagonist SQ29548. Using a human TP receptor riboprobe, Northern blotting of mRNA isolated from the stingray kidney identified transcripts of 2.8 and 6kb. The 2.8kb transcript is similar to a 2.8kb transcript found in human cells or tissues, but the 6kb transcript may be unique. These data indicate the presence of a TXB(2)-like substance in the blood, a TP receptor in the kidney, TXA(2) biological activity in the ventral aorta, and expression of a TP receptor-like gene.
authors.affiliation: Grice Marine Laboratory, College of Charleston, Charleston, South Carolina, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Cabrera
authors.forename: Michael G
authors.initials: MG
authors.lastname: Janech
authors.forename: Thomas A
authors.initials: TA
authors.lastname: Morinelli
authors.forename: Donald H
authors.initials: DH
authors.lastname: Miller
mesh_terms: D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000378:metabolism*; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D018940:Elasmobranchii / Q000502:physiology*; D005260:Female; D066298:In Vitro Techniques; D007213:Indomethacin / Q000494:pharmacology; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D009119:Muscle Contraction / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D017482:Receptors, Thromboxane / Q000378:metabolism; D013928:Thromboxane A2 / Q000097:blood / Q000378:metabolism*; D013929:Thromboxane B2 / Q000097:blood / Q000378:metabolism*
chemical_list: D016861:Cyclooxygenase Inhibitors; D017482:Receptors, Thromboxane; D013929:Thromboxane B2; D013928:Thromboxane A2; D007213:Indomethacin