An endogenous 'hypertensive factor' enhances the voltage-dependent calcium current.
The effects of an immunoaffinity-purified putative endogenous hypertensive factor (HF) on voltage-dependent calcium current in frog cardiac myocytes were assessed. In 9 out of 10 cells, HF reversibly increased the peak amplitude of the calcium current. HF increased peak calcium current density at -5 mV from a control level of 1.8 +/- 1.3 pA/pF (mean +/- SD) to 4.4 +/- 2.0 pA/pF. HF shifted the peak of the calcium current-voltage relationship in the hyperpolarizing direction. HF shifted the voltage dependence of the inactivation of the calcium current to more negative potentials with prepulses from -80 to 0 mV, but the inactivation was not affected with prepulses more positive than 0 mV. Modulation of the voltage-dependent calcium current by HF may be the mechanism underlying its pressor effects.
Simmons
M A
MA
Biomedical Sciences Graduate Program, Marshall University School of Medicine, Huntington, WV 25755.
Johnson
E C
EC
Becker
J B
JB
Todd
D G
DG
Reichenbecher
V E
VE
McCumbee
W D
WD
Wright
G L
GL
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects*; D002478:Cells, Cultured; D004563:Electrochemistry; D004912:Erythrocytes / Q000032:analysis; D006321:Heart / Q000187:drug effects*; D006973:Hypertension / Q000097:blood*; D009206:Myocardium / Q000166:cytology; D010455:Peptides / Q000302:isolation & purification / Q000494:pharmacology*; D051381:Rats
D015220:Calcium Channels; D010455:Peptides; D002118:Calcium