Atrial natriuretic peptide reduces the basal level of cytosolic free Ca2+ in guinea pig cardiac myocytes.
The cytosolic free Ca2+ concentration ([Ca2+]i) was monitored in quiescent atrial and ventricular myocytes isolated from guinea-pig hearts by the fura-2 fluorescence ratio technique. Recombinant human atrial natriuretic peptide (ANP) was found to reduce their basal [Ca2+]i level in a dose-dependent manner. Dibutyryl-cGMP mimicked the effect of ANP. Neither the prior application of caffeine nor removal of extracellular Na+ impaired the ANP effect. ANP had no inhibitory effect on voltage-gated Ca2+ currents measured by a whole-cell patch clamp technique. The ANP-induced [Ca2+]i decrease was abolished by orthovanadate. Thus, it is concluded that ANP reduces the basal [Ca2+]i presumably through the cGMP-mediated activation of the plasma membrane Ca2(+)-pump in cardiac myocytes.
Tei
M
M
Department of Molecular Diagnostics, Kyoto University Faculty of Medicine, Japan.
Horie
M
M
Makita
T
T
Suzuki
H
H
Hazama
A
A
Okada
Y
Y
Kawai
C
C
D000818:Animals; D016275:Atrial Function; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D003994:Bucladesine / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D006168:Guinea Pigs; D006325:Heart Atria / Q000187:drug effects / Q000378:metabolism; D006352:Heart Ventricles / Q000187:drug effects / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D011188:Potassium / Q000494:pharmacology; D016276:Ventricular Function
D015220:Calcium Channels; D003994:Bucladesine; D009320:Atrial Natriuretic Factor; D011188:Potassium