Mechanical performance of an in situ perfused heart from the turtle Chrysemys scripta during normoxia and anoxia at 5°C and 15°C

Farrell, A. P., Franklin, C. E., Arthur, P. G., Thorarensen, H. and Cousins, K. L. (1994) Mechanical performance of an in situ perfused heart from the turtle Chrysemys scripta during normoxia and anoxia at 5°C and 15°C. Journal of Experimental Biology, 191 207-229.

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Author Farrell, A. P.
Franklin, C. E.
Arthur, P. G.
Thorarensen, H.
Cousins, K. L.
Title Mechanical performance of an in situ perfused heart from the turtle Chrysemys scripta during normoxia and anoxia at 5°C and 15°C
Formatted title
Mechanical performance of an in situ perfused heart from the turtle Chrysemys scripta during normoxia and anoxia at 5°C and 15°C
Journal name Journal of Experimental Biology   Check publisher's open access policy
ISSN 0022-0949
1477-9145
Publication date 1994-06
Sub-type Article (original research)
Open Access Status File (Publisher version)
Volume 191
Start page 207
End page 229
Total pages 23
Place of publication Cambridge, United Kingdom
Publisher The Company of Biologists
Language eng
Formatted abstract
We developed an in situ perfused turtle (Chrysemys scripta) heart preparation to study its intrinsic mechanical properties at 5 ˚C and 15 ˚C using normoxic and anoxic perfusion conditions. The in situ preparation proved durable and stable. At 15 ˚C and a spontaneous heart rate of 23.4 beats min-1, maximum stroke volume was 2.54 ml kg-1 body mass, maximum cardiac output was 62.5 ml min-1 kg-1 and maximum cardiac myocardial power output was 1.50 mW g-1 ventricular mass. There was good agreement between these values and those previously obtained in vivo. Furthermore, since the maximum stroke volume observed here was numerically equivalent to that observed in ventilating C. scripta in vivo, it seems likely that C. scripta has little scope to increase stroke volume to a level much beyond that observed in the resting animal through intrinsic mechanisms alone. The ability of the perfused turtle heart to maintain stroke volume when diastolic afterload was raised (homeometric regulation) was relatively poor. At 5 ˚C, the spontaneous heart rate (8.1 beats min-1) was threefold lower and homeometric regulation was impaired, but maximum stroke volume (2.25 ml kg-1) was not significantly reduced compared with the value at 15 ˚C. The significantly lower maximum values for cardiac output (18.9 ml min-1 kg-1) and power output (0.39 mW g-1 ventricular mass) at 5 ˚C were largely related to pronounced negative chronotropy with only a relatively small negative inotropy. Anoxia had weak negative chronotropic effects and marked negative inotropic effects at both temperatures. Negative inotropy affected pressure development to a greater degree than maximum flow and this difference was more pronounced at 5 ˚C than at 15 ˚C. The maximum anoxic cardiac power output value at 15 ˚C (0.77 mW g-1 ventricular mass) was not that different from values previously obtained for the performance of anoxic rainbow trout and hagfish hearts. In view of this, we conclude that the ability of turtles to overwinter under anoxic conditions depends more on their ability to reduce cardiac work to a level that can be supported through glycolysis than on their cardiac glycolytic potential being exceptional.
Keyword Temperature
Heart
Anoxia
Heart rate
Cardiac output
Turtle
Chrysemys scripta
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Biological Sciences Publications
 
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