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An endogenous 'hypertensive factor' enhances the voltage-dependent calcium current.
M A Simmons1, E C Johnson, J B Becker
1Biomedical Sciences Graduate Program, Marshall University School of Medicine, Huntington, WV 25755.
FEBS Letters
|August 28, 1989
Summary
A hypertensive factor (HF) significantly increases calcium current amplitude and alters its voltage dependence in frog heart cells. This modulation of calcium channels may explain HF's blood pressure-raising effects.
Area of Science:
- Cardiovascular Physiology
- Electrophysiology
- Molecular Cardiology
Background:
- Hypertension is a complex cardiovascular condition with multifactorial origins.
- Endogenous factors influencing cardiac function are crucial for understanding blood pressure regulation.
- Voltage-dependent calcium currents play a vital role in cardiac contractility and electrophysiology.
Purpose of the Study:
- To investigate the effects of an immunoaffinity-purified endogenous hypertensive factor (HF) on cardiac calcium currents.
- To elucidate the potential mechanism by which HF exerts its pressor effects at the cellular level.
Main Methods:
- Patch-clamp electrophysiology was used to record voltage-dependent calcium currents in isolated frog cardiac myocytes.
- Cardiac myocytes were exposed to purified putative endogenous hypertensive factor (HF).
- Calcium current amplitude, voltage dependence, and inactivation kinetics were analyzed.
Main Results:
- Hypertensive factor (HF) significantly increased the peak amplitude of voltage-dependent calcium current in 90% of tested cells.
- HF enhanced peak calcium current density from 1.8 +/- 1.3 pA/pF to 4.4 +/- 2.0 pA/pF at -5 mV.
- HF induced a hyperpolarizing shift in the calcium current-voltage relationship and altered inactivation kinetics.
Conclusions:
- The endogenous hypertensive factor (HF) directly modulates cardiac voltage-dependent calcium channels.
- Increased calcium influx due to HF action on these channels may underlie its pressor effects.
- Further research is warranted to identify HF and its precise role in hypertension.