Format

Send to

Choose Destination
See comment in PubMed Commons below
Am J Physiol. 1989 Nov;257(5 Pt 2):R1046-9.

Freezing-induced changes in the heart rate of wood frogs (Rana sylvatica).

Author information

1
Department of Biology, Nazareth College, Rochester, New York 14610.

Abstract

During the first few hours of freezing the cardiovascular system must distribute cryoprotectant throughout the body of freeze-tolerant frogs. This study presents initial documentation of the changes in heart rate of wood frogs (Rana sylvatica) during nonlethal freezing. Heart rate was determined by measuring the electrocardiogram of frogs. Within 1 min of the onset of freezing the heart rate nearly doubled to approximately 8.0 beats/min. The heart rate began to slow after the first hour of the freeze, and the heart completely stopped beating near the completion of ice formation approximately 20 h later. Recordings from a single frog revealed that the heart beat resumes within 1 h after thawing and near-normal function is achieved after only a few hours. The release of the latent heat of fusion caused a rise in body temperature (1.7 degrees C) for a few hours and was closely correlated with an increase in the heart rate. However, other factors such as reduction in blood volume, increase in blood viscosity, and progressive hypoxia may prominently influence cardiac function indirectly. Regardless, the heart functions long enough to distribute glucose throughout the body during the first few hours of the freeze.

PMID:
2589531
[Indexed for MEDLINE]
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for HighWire
    Loading ...
    Support Center