title: The adrenomedullary venous vasculature as a target for endothelins: comparison of the porcine and bovine central adrenomedullary veins.
abstract: The functional properties of the isolated porcine and bovine central adrenomedullary veins were compared, with emphasis on the active tension responses to high K+, endothelin-1 (ET-1) and neuropeptide Y (NPY). In the porcine vein, the contraction evoked by ET-1 was 4--5-fold higher than with high K+, as in the bovine vein. The potencies for ET-1 were similar in ring and strip preparations of the porcine vein, with EC50 values 5--7-fold higher than in the bovine vein. In preparations previously exposed to ET-1 the contractions evoked by high K+ and NPY were potentiated and facilitated, respectively,. However, only in the porcine vein was the ET-1 contraction sustained. This contraction was effectively relaxed by milrinone, indicating a role for cGMP inhibited cyclic nucleotide phosphodiesterase in the sustained contraction. Caffeine and forskolin were also effective relaxants of contractions evoked by ET-1 in both veins, suggesting relaxation by elevated levels of cAMP. The K(+)-contracted porcine, but not bovine, vein was relaxed by acetylcholine (ACh) and vasointestinal polypeptide in a concentration-dependent manner, indicating species differences with respect to signal transduction leading to increases in cyclic nucleotides. In conclusion, these results demonstrate that ET-1 is the main constrictor of the porcine central adrenomedullary vein, with significant species differences in mode of contraction and relaxation. These findings suggest roles for the endogeneously released ET-1 and NPY in regulation of venous contractility within the adrenal gland of mammals.
authors.affiliation: Department of Physiology, University of Bergen, Norway.
authors.forename: H
authors.initials: H
authors.lastname: Bjerkås
authors.forename: K
authors.initials: K
authors.lastname: Lønning
authors.forename: K B
authors.initials: KB
authors.lastname: Helle
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism; D000313:Adrenal Medulla / Q000098:blood supply*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002417:Cattle / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D019332:Endothelin-1 / Q000494:pharmacology*; D020105:Milrinone / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects; D009478:Neuropeptide Y / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin / Q000187:drug effects / Q000502:physiology; D015290:Second Messenger Systems / Q000502:physiology; D013045:Species Specificity; D013552:Swine / Q000502:physiology*; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology; D014680:Veins / Q000187:drug effects
chemical_list: D019332:Endothelin-1; D009478:Neuropeptide Y; D044022:Receptor, Endothelin A; D017466:Receptors, Endothelin; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D005576:Colforsin; D014660:Vasoactive Intestinal Peptide; D002110:Caffeine; D011433:Propranolol; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D020105:Milrinone; D000109:Acetylcholine; D011188:Potassium