Determinants of coronary blood flow in sandbar sharks, Carcharhinus plumbeus.
The coronary circulation first appeared in the chordate lineage in cartilaginous fishes where, as in birds and mammals but unlike most teleost fishes, it supplies arterial blood to the entire myocardium. Despite the pivotal position of elasmobranch fishes in the evolution of the coronary circulation, the determinants of coronary blood flow have never been investigated in this group. Elasmobranch fishes are of special interest because of the morphological arrangement of their cardiomyocytes. Unlike teleosts, the majority of the ventricular myocardium in elasmobranch fishes is distant to the venous blood returning to the heart (i.e., the luminal blood). Also, the majority of the myocardium is in close association with the coronary circulation. To determine the relative contribution of the coronary and luminal blood supplies to cardiovascular function in sandbar sharks, Carcharhinus plumbeus, we measured coronary blood flow while manipulating cardiovascular status using acetylcholine and adrenaline. By exploring inter- and intra-individual variation in cardiovascular variables, we show that coronary blood flow is directly related to heart rate (R2= 0.6; P < 0.001), as it is in mammalian hearts. Since coronary blood flow is inversely related to coronary resistance both in vivo and in vitro, we suggest that in elasmobranch fishes, changes in heart rate mediate changes in coronary vascular resistance, which adjust coronary blood flow appropriately.
Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada. cox@zoology.ubc.ca.
Georgina K
GK
Cox
National Marine Fisheries Service, Northeast Fisheries Science Center, James J. Howard Marine Sciences Laboratory, Highlands, NJ, USA.
Richard W
RW
Brill
Washington and Lee University, Lexington, VA, USA.
Kaitlin A
KA
Bonaro
Department of Zoology, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada.|Faculty of Land and Food Systems, University of British Columbia, Vancouver, BC, Canada.
Anthony P
AP
Farrell
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D062186:Arterial Pressure / Q000187:drug effects; D002302:Cardiac Output / Q000187:drug effects; D018679:Cholinergic Agonists / Q000494:pharmacology; D003326:Coronary Circulation / Q000187:drug effects / Q000502:physiology*; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D006321:Heart / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D012754:Sharks / Q000502:physiology*
D018679:Cholinergic Agonists; D000109:Acetylcholine; D004837:Epinephrine
Cardiac power output; Coronary blood flow; Coronary resistance; Heart rate; Sharks
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