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Modulation of heart glycogen by isoproterenol‐induced transient tachycardia in newly born rats
Author(s) -
Fewell James Edwin,
Zhang Chunfen
Publication year - 2012
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.26.1_supplement.lb622
Subject(s) - glycogen , medicine , heart rate , endocrinology , tachycardia , hypoxia (environmental) , chemistry , blood pressure , organic chemistry , oxygen
Newly born animals of a number of species have an increased cardiac glycogen content compared to older animals which is purported to support cardiac function and promote survival during hypoxia. As a first step in investigating the role of cardiac glycogen in influencing protective responses of newly born rat pups to hypoxia, our experiments were carried out to determine if cardiac glycogen would be altered following isoproterenol(ISO)‐induced transient tachycardia. In preliminary dose–response experiments testing doses of 0 to 10 mg/kg of the nonselective beta adrenergic receptor agonist ISO, we determined 1.25 mg/kg to be the smallest dose that elicited a maximal heart rate response (i.e., the EC 100 ) in 1 day‐old pups and in which the heart rate returned back to control levels by 120 minutes. One day old rat pups received vehicle (VEH) or ISO (1.25 mg/kg) ip and heart rate was recorded for 120 min before decapitation and removal of the heart for determination of glycogen content. Whole heart glycogen content in untouched pups was 4.1±0.5 mg/g of tissue (n=4). Whole heart glycogen content decreased significantly (p<0.05) following ISO‐induced transient tachycardia compared to VEH: 1.5±0.5 mg/g (n=8) versus 3.5±0.3 mg/g (n=5), respectively. Thus, our data provide evidence that whole heart glycogen is significantly decreased in newly born rat pups following ISOinduced transient tachycardia.