Phosphatidic acid increases in response to noradrenaline and endothelin-1 in adult rabbit ventricular myocytes.
OBJECTIVE
The aim was to assess whether noradrenaline and endothelin-1 can stimulate endogenous production of phosphatidic acid in adult ventricular myocytes.


METHODS
After stimulation of rabbit ventricular myocytes with noradrenaline and endothelin-1, total lipids were extracted using the Bligh and Dyer procedure and separated by thin layer chromatography, and phosphatidic acid was quantified using photodensitometric analysis of visualised lipids with CuSO4/H3PO4.


RESULTS
Noradrenaline (10(-5) M) elicited a rapid increase in phosphatidic acid at 2 min, followed by a decrease at 5 min. A second delayed and sustained increase in phosphatidic acid occurred at 10 min. The response to noradrenaline (10(-9) to 10(-5) M) was concentration dependent with a half maximum response (EC50) of 3.1 x 10(-8) M and the maximum effect at 10(-6) M. The increase in phosphatidic acid production in response to noradrenaline was abolished by an alpha 1 adrenergic receptor blocking agent (2-[beta-(4-hydroxyphenyl)-ethylaminomethyl]tetralone) but unaffected by the beta adrenergic blocking agent L-propranolol. An increase in phosphatidic acid was also elicited in rabbit ventricular myocytes in response to endothelin-1. The response was time and concentration dependent with the maximal increase at 12 min, EC50 5.3 x 10(-9) M, and maximum effect at 10(-6) M. Both noradrenalin and endothelin-1 stimulated phosphatidylbutanol production in the presence of butanol (100 mM), indicating that both agonists activate phospholipase D.


CONCLUSIONS
Noradrenaline at physiological concentrations elicits both a rapid and a delayed increase in phosphatidic acid in adult rabbit ventricular myocytes. Endothelial-1, at physiological concentrations, also stimulates an increase in the mass of phosphatidic acid in myocytes, but the increase induced by endothelin-1 is monophasic, in contrast to the biphasic response seen during stimulation with noradrenaline. Activation of phospholipase D contributes to the increase in phosphatidic acid seen during stimulation of myocytes with either noradrenaline or endothelin-1. These are the first data to characterise endogenous production of phosphatidic acid in isolated adult ventricular myocytes.
Ye
H
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Department of Internal Medicine, Washington University School of Medicine, St Louis, MO 63110.
Wolf
R A
RA
Kurz
T
T
Corr
P B
PB
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D016232:Endothelins / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects; D007700:Kinetics; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology*; D010627:Phenethylamines / Q000494:pharmacology; D010712:Phosphatidic Acids / Q000378:metabolism*; D010739:Phospholipase D / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D011817:Rabbits; D013268:Stimulation, Chemical; D044024:Tetralones; D013997:Time Factors
D000317:Adrenergic alpha-Antagonists; D016232:Endothelins; D010627:Phenethylamines; D010712:Phosphatidic Acids; D044024:Tetralones; C010652:BE 2254; D011433:Propranolol; D010739:Phospholipase D; D009638:Norepinephrine