Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol 50, Issue 4 B224-B231, Copyright © 1995 by The Gerontological Society of America
The force-interval relation in aged hamster heart
SE Howlett and J Bobet
Department of Pharmacology, Dalhousie University, Halifax, Nova Scotia.
This study determined whether aging affects the force-interval relation in
cardiac muscle. Isolated left atria from young (60-120 days) and old (>
535 days) adult hamsters were paced at 1 Hz, and effects of interposing
test intervals (0.3-600 sec) on the force of a test beat following the
interval (force-interval relation) were examined. To quantify differences,
force-interval curves were fitted with an equation which used five
parameters to define the shape. At test intervals < 10 sec,
force-interval curves were similar in young and aged hearts. At longer
intervals, however, force was greater in atria from old animals than in
atria from young animals. The parameters E0, which reflects force amplitude
at long intervals, was significantly increased in old atria while the
parameter gamma, which reflects the time course of force decay at long
intervals, was significantly reduced. Thus, at long test intervals the
force-interval relation is markedly affected by the aging process.
