CORONARY HEMODYNAMICS IN ELASMOBRANCHS AND TELEOSTS

Until recently, direct measurements of coronary blood flow in fishes h ad not been made. This review presents and compares in vivo measuremen ts of coronary flow recorded from the school shark Galeorhinus austral is, and the coho salmon, Oncorhynchus kisutch. rn both species, the co ronary blood flow was phasic and strongly influenced by the cardiac cy cle. Coronary blood flow in the school shark was more severely comprom ised by the cardiac cycle with a short retrograde flow occurring durin g systole. In the coho salmon, there was an anterograde coronary blood flow throughout the cardiac cycle. Differences in coronary hemodynamic s are discussed in relation to differences in the myoarchitecture of t he school shark and coho salmon hearts. The regulation of coronary blo od flow through changes in vascular resistance (vasoactivity of the co ronary vessels) is also discussed.