title: Vasopressin-mediated enhancement of adrenergic vasoconstriction involves both the tyrosine kinase and the protein kinase C pathways.
abstract: BACKGROUND
  Vasopressin is frequently used to treat catecholamine-resistant vasodilatory shock. It enhances the vasoconstrictor effects of catecholamines at concentrations of vasopressin that have none or only minimal intrinsic pressor effects. However, the vascular mechanisms underlying this combined pharmacological approach have not been fully elucidated.
  
  
  METHODS
  We used isometric tension measurements in vascular rings to investigate potential cellular mechanisms. Vascular rings (0.2 mm diameter) were harvested from the superior mesenteric artery of Wistar rats (2 to 4 months of age). Dose-response relationships were derived for vasopressin (VP) and norepinephrine (NE), in the absence and presence of a subpressor dose of VP (10(-9) M). The contribution of tyrosine kinase (TK), the TK pathway proteins SRC and PYK2, as well as protein kinase C (PKC) were determined by measuring the modulating influence of specific inhibitors on the pressor response to NE (10(-5) M) alone and the augmented pressor response to VP (10(-9) M).
  
  
  RESULTS
  VP (10(-9) M) had only minimal pressor effect alone (10% of maximal response), but significantly increased the E(max) response to NE (587.8 ± 40.7 vs 331.2 ± 10.4 mg). TK inhibition completely abolished the pressor response to NE (100% vs 1.0% 0.5%) and the augmented VP response alone (100% vs 2.0% ± 1.01%). Both responses were significantly, but equally, decreased by SRC inhibition (63% ± 4.0% and 69% 1.0%). In contrast, inhibition of the TK molecule PYK2 with salicylate had differential inhibitory effects on the vasoconstrictor responses. Salicylate caused a greater inhibition of VP-induced augmented NE response in comparison with NE alone (62.1% ± 7% and 15% ± 2%). Inhibition of either the µ or γ PKC isoform significantly decreased both responses, but the magnitude of the inhibition was significantly different for each isoform. Inhibition of the γ PKC isoform significantly decreased the vasoconstriction responses to both NE and VP plus NE (82.9 ± 3.9 vs 32.8 ± 3.8). Inhibition of the µ PKC isoform significantly decreased both responses and completely abolished the VP-augmented response to NE.
  
  
  CONCLUSIONS
  These data are consistent with a central role for TK in mediating both the NE response and the VP-augmented response. Moreover, PYK2 and the µ and γ isoforms of PKC seem to play a preferential role in mediating the augmented VP response. The apparent divergent roles of these pathways in mediating NE- versus VP-augmented pressor responses could potentially lead to new targeted therapies in catecholamine-resistant shock.
authors.affiliation: Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University, 600 North Wolfe Street Tower 711, Baltimore, MD 21287, USA.
authors.forename: Jochen
authors.initials: J
authors.lastname: Steppan
authors.forename: Sineád M
authors.initials: SM
authors.lastname: Nyhan
authors.forename: Gautam
authors.initials: G
authors.lastname: Sikka
authors.forename: Jorge
authors.initials: J
authors.lastname: Uribe
authors.forename: Ayushi
authors.initials: A
authors.lastname: Ahuja
authors.forename: Anthony R
authors.initials: AR
authors.lastname: White
authors.forename: Artin A
authors.initials: AA
authors.lastname: Shoukas
authors.forename: Dan E
authors.initials: DE
authors.lastname: Berkowitz
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019833:Genistein / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000502:physiology; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010276:Parasympatholytics / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D012459:Salicylates / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects*; D013564:Sympathetic Nervous System / Q000187:drug effects*; D014661:Vasoconstriction / Q000187:drug effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014667:Vasopressins / Q000494:pharmacology*
chemical_list: D004791:Enzyme Inhibitors; D007527:Isoenzymes; D010276:Parasympatholytics; D047428:Protein Kinase Inhibitors; D012459:Salicylates; D014662:Vasoconstrictor Agents; D014667:Vasopressins; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D009638:Norepinephrine