title: Exaggerated coronary vasoreactivity to endothelin-1 in aged rats: role of protein kinase C.
abstract: OBJECTIVE
  The interaction between advanced age and increased susceptibility to ischemic insult is well documented. Age-related increases in coronary vascular resistance, in part due to impaired dilator responses, have been reported. Our aim was to determine the role of endothelin-1 (ET-1) on enhanced constrictor responses in aged coronary arteries (CAs) and whether protein kinase C (PKC) signaling mechanisms impact ET-1 responses.
  
  
  METHODS
  Vasoreactivity was assessed in CAs isolated from aged (24 months; n=16) and adult (4 months; n=21) male F344 rats following ET-1 (10(-10)-10(-8)) with and without specific ETA/ETB receptor antagonists (BQ-123, 1 microM; BQ-788, 30 nM) or the PKC inhibitor bisindolylmaleimide (Bis; 10(-6) M). Constrictor responses to KCl (80 mM) were also measured and voltage-gated Ca2+ channel (VGCC) determined in isolated coronary smooth muscle cells. Dilator responses to acetylcholine (ACH) and sodium nitroprusside (SNP) were assessed.
  
  
  RESULTS
  Passive diameter was greater (357+/-19 vs. 309+/-9; p<0.02) while spontaneous tone was similar in 24 months vs. 4 months. ET-1 resulted in greater constriction in 24 months vs. 4 months (79% vs. 67%; p<0.01). Group differences persisted following selective ETB inhibition with BQ-788 (p<0.02), while BQ-123 abolished contractile responses to ET-1. Importantly, inhibition of ET-1 constriction by Bis occurred in 24 months but not 4 months (p<0.01). Constrictor responses to KCl and peak VGCC current density were similar in 24 months vs. 4 months (48% vs. 50%). No age-related differences were observed in ACH- or SNP-mediated dilation. Western blotting revealed increases in Ca2+-sensitive PKCalpha, -betaI, and -betaII levels with age, while eNOS and ETA receptor protein levels were unchanged.
  
  
  CONCLUSIONS
  Aberrant ETA constrictor responses and directional changes in PKC are likely to contribute to coronary vascular pathology with advanced age.
authors.affiliation: Department of Kinesiology, The Pennsylvania State University, 106 Noll Laboratory, University Park, PA 16802, USA. dhk102@psu.edu
authors.forename: Donna H
authors.initials: DH
authors.lastname: Korzick
authors.forename: Judy M
authors.initials: JM
authors.lastname: Muller-Delp
authors.forename: Patrick
authors.initials: P
authors.lastname: Dougherty
authors.forename: Christine L
authors.initials: CL
authors.lastname: Heaps
authors.forename: Douglas K
authors.initials: DK
authors.lastname: Bowles
authors.forename: Kevin K
authors.initials: KK
authors.lastname: Krick
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D020865:Calcium Channels, P-Type / Q000378:metabolism; D003331:Coronary Vessels / Q000187:drug effects* / Q000378:metabolism; D065130:Endothelin A Receptor Antagonists; D065131:Endothelin B Receptor Antagonists; D019332:Endothelin-1 / Q000494:pharmacology*; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D051381:Rats; D011916:Rats, Inbred F344; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
chemical_list: D020865:Calcium Channels, P-Type; D065130:Endothelin A Receptor Antagonists; D065131:Endothelin B Receptor Antagonists; D019332:Endothelin-1; D007211:Indoles; D008301:Maleimides; D009842:Oligopeptides; D010456:Peptides, Cyclic; D010880:Piperidines; D014662:Vasoconstrictor Agents; C086539:BQ 788; D011189:Potassium Chloride; D011493:Protein Kinase C; C088060:bisindolylmaleimide; C072247:cyclo(Trp-Asp-Pro-Val-Leu)