[Atrial natriuretic factor diminishes the contractility of the cardiac cell in culture].
The hypotensive effect of ANP has been associated with lowered cardiac output. Although only minor or no negative inotropic effect was found in vitro, a direct myocardial depressant effect of ANP remains a possible mechanism in vitro, in addition to the reduction in cardiac preload. Therefore we tested the hypothesis of a direct negative inotropic effect of ANP on the cultured chick embryo ventricular cell, an experimental system which contains no neural elements and no endogenous neurotransmitters. ANP (rat-ANP 1-23) 10(-8) M significantly and reversibly decreased contractility in spontaneously beating cells. A further decrease (-30 +/- 4 p. 100 of initial amplitude of contraction) was observed at 2.5 x 10(-7) M: -17 +/- 4 p. 100 of initial amplitude). The positive inotropic effect of angiotensin II (2.5 x 10(-7) M) on spontaneously beating cells was fully antagonized by ANP (2.5 x 10(-7) M) and amplitude of contraction decreased under control levels. By contrast (1) the increase in contractility in response to extra-cellular calcium (increased from 1.5 to 2.1 mM) was significantly less altered by ANP and (2) the time-course of the positive inotropic effect of the calcium-channel agonist BAY K 8644 (5 x 10(-9) M) or the beta-adrenergic agonist isoproterenol (10(-6) M) was unchanged by ANP. These results indicate a direct negative inotropic effect of ANP (1-23) on cultured chick heart cells and suggest an effect on intracellular messengers involved in the cardiac effects of angiotensin II.(ABSTRACT TRUNCATED AT 250 WORDS)
Vaxelaire
J F
JF
INSERM U 228, Paris.
Laurent
S
S
Briand
V
V
Michel
J B
JB
Schmitt
H
H
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000804:Angiotensin II / Q000037:antagonists & inhibitors; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D002118:Calcium / Q000494:pharmacology; D002478:Cells, Cultured; D002642:Chick Embryo; D003864:Depression, Chemical; D004558:Electric Stimulation; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D009200:Myocardial Contraction / Q000187:drug effects*
D000804:Angiotensin II; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009320:Atrial Natriuretic Factor; D007545:Isoproterenol; D002118:Calcium
Le facteur atrial natriurétique diminue la contractilité de la cellule cardiaque en culture.