Abstract
We used standard microelectrode techniques to study the developmental changes and β-adrenergic modulation of membrane potential and of Na-K pump activity in adult (>1 yr of age) and neonatal (2-10 days) canine Purkinje fibers. Isoproterenol (10-7 M) increased the rate of development and magnitude of pacing-induced hyperpolarization of adult fibers driven at a 1- s cycle length. This effect of isoproterenol was attenuated by treating dogs with pertussis toxin (PTX), (30 μg/kg). Other adult and neonatal fibers were superfused with a Tyrode solution containing Ba2+ 0.2 mM, Cs+ 2 mM, and 10-6 M verapamil, thus leading to depolarization and cessation of spontaneous activity. The Na-K pump was studied by alternating solutions containing [K] at 0 mM (inhibiting the pump) and 4 mM (reactivating the pump). Although the kinetics of the Na-K pump appeared faster in neonatal fibers than in adult fibers, measurement of cell surface-to-volume ratio compensated for the difference. We therefore conclude that 1) the apparent age-related changes in Na-K pump activity in canine Purkinje fibers in fact reflect cell surface-to-volume ratio and, 2) the β-adrenergic agonist- induced hyperpolarization in adults requires the presence of a PTX-sensitive G protein for its occurrence.
| Original language | English (US) |
|---|---|
| Journal | American Journal of Physiology - Heart and Circulatory Physiology |
| Volume | 271 |
| Issue number | 2 40-2 |
| State | Published - Aug 1996 |
| Externally published | Yes |
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Keywords
- autonomic nervous system
- G protein
- isoproterenol
- pertussis toxin
ASJC Scopus subject areas
- Physiology
- Physiology (medical)
Cite this
β-adrenergic modulation of Na-K pump activity in young and adult canine cardiac Purkinje fibers. / Charpentier, Flavien; Legato, Marianne J.; Steinberg, Susan F.; Cohen, Ira S.; Rosen, Michael R.
In: American Journal of Physiology - Heart and Circulatory Physiology, Vol. 271, No. 2 40-2, 08.1996.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - β-adrenergic modulation of Na-K pump activity in young and adult canine cardiac Purkinje fibers
AU - Charpentier, Flavien
AU - Legato, Marianne J.
AU - Steinberg, Susan F.
AU - Cohen, Ira S.
AU - Rosen, Michael R.
PY - 1996/8
Y1 - 1996/8
N2 - We used standard microelectrode techniques to study the developmental changes and β-adrenergic modulation of membrane potential and of Na-K pump activity in adult (>1 yr of age) and neonatal (2-10 days) canine Purkinje fibers. Isoproterenol (10-7 M) increased the rate of development and magnitude of pacing-induced hyperpolarization of adult fibers driven at a 1- s cycle length. This effect of isoproterenol was attenuated by treating dogs with pertussis toxin (PTX), (30 μg/kg). Other adult and neonatal fibers were superfused with a Tyrode solution containing Ba2+ 0.2 mM, Cs+ 2 mM, and 10-6 M verapamil, thus leading to depolarization and cessation of spontaneous activity. The Na-K pump was studied by alternating solutions containing [K] at 0 mM (inhibiting the pump) and 4 mM (reactivating the pump). Although the kinetics of the Na-K pump appeared faster in neonatal fibers than in adult fibers, measurement of cell surface-to-volume ratio compensated for the difference. We therefore conclude that 1) the apparent age-related changes in Na-K pump activity in canine Purkinje fibers in fact reflect cell surface-to-volume ratio and, 2) the β-adrenergic agonist- induced hyperpolarization in adults requires the presence of a PTX-sensitive G protein for its occurrence.
AB - We used standard microelectrode techniques to study the developmental changes and β-adrenergic modulation of membrane potential and of Na-K pump activity in adult (>1 yr of age) and neonatal (2-10 days) canine Purkinje fibers. Isoproterenol (10-7 M) increased the rate of development and magnitude of pacing-induced hyperpolarization of adult fibers driven at a 1- s cycle length. This effect of isoproterenol was attenuated by treating dogs with pertussis toxin (PTX), (30 μg/kg). Other adult and neonatal fibers were superfused with a Tyrode solution containing Ba2+ 0.2 mM, Cs+ 2 mM, and 10-6 M verapamil, thus leading to depolarization and cessation of spontaneous activity. The Na-K pump was studied by alternating solutions containing [K] at 0 mM (inhibiting the pump) and 4 mM (reactivating the pump). Although the kinetics of the Na-K pump appeared faster in neonatal fibers than in adult fibers, measurement of cell surface-to-volume ratio compensated for the difference. We therefore conclude that 1) the apparent age-related changes in Na-K pump activity in canine Purkinje fibers in fact reflect cell surface-to-volume ratio and, 2) the β-adrenergic agonist- induced hyperpolarization in adults requires the presence of a PTX-sensitive G protein for its occurrence.
KW - autonomic nervous system
KW - G protein
KW - isoproterenol
KW - pertussis toxin
UR - http://www.scopus.com/inward/record.url?scp=0029760281&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0029760281&partnerID=8YFLogxK
M3 - Article
C2 - 8770114
AN - SCOPUS:0029760281
VL - 271
JO - American Journal of Physiology
JF - American Journal of Physiology
SN - 0363-6135
IS - 2 40-2
ER -