title: Increased intracellular [dATP] enhances cardiac contraction in embryonic chick cardiomyocytes.
abstract: Although ATP is the physiological substrate for cardiac contraction, cardiac contractility is significantly enhanced in vitro when only 10% of ATP substrate is replaced with 2'-deoxy-ATP (dATP). To determine the functional effects of increased intracellular [dATP] ([dATP](i)) within living cardiac cells, we used hypertonic loading with varying exogenous dATP/ATP ratios, but constant total nucleotide concentration, to elevate [dATP](i) in contractile monolayers of embryonic chick cardiomyocytes. The increase in [dATP](i) was estimated from dilution of dye added in parallel with dATP. Cell viability, average contractile amplitude, rates of contraction/relaxation, spontaneous beat frequency, and Ca2+ transient amplitude and kinetics were examined. At total [dATP](i) above approximately 70 microM, spontaneous contractions ceased, and above approximately 100 microM [dATP](i), membrane blebbing was also observed, consistent with apoptosis. Interestingly, [dATP](i) of approximately 60 microM ( approximately 40% increase over basal [dATP](i) levels) enhanced both amplitude of contraction and the rates of contraction and relaxation without affecting beat frequency. With total [dATP](i) of approximately 60 microM or less, we found no significant change in Ca2+ transients. These data indicate that there is an "optimal" concentration of exogenously loaded [dATP](i) that under controlled conditions can enhance contractility in living cardiomyocytes without affecting beat frequency or Ca2+ transients.
authors.affiliation: Institute of Molecular Biophysics, Florida State University, Tallahassee, Florida, USA. bschoffstall@mail.barry.edu
authors.forename: Brenda
authors.initials: B
authors.lastname: Schoffstall
authors.forename: P Bryant
authors.initials: PB
authors.lastname: Chase
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002642:Chick Embryo; D003838:Deoxyadenine Nucleotides / Q000494:pharmacology*; D006982:Hypertonic Solutions / Q000494:pharmacology; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism*; D009200:Myocardial Contraction / Q000187:drug effects*; D032383:Myocytes, Cardiac / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D012235:Rhodamines / Q000378:metabolism
chemical_list: D003838:Deoxyadenine Nucleotides; D006982:Hypertonic Solutions; D012235:Rhodamines; C026600:2'-deoxyadenosine triphosphate