Gq/11-coupled receptors and protein synthesis in rat cardiomyocytes: role of Gi-proteins and protein kinase C-isozymes.
Our recent findings indicate that, in rat neonatal ventricular cardiomyocytes, endothelin-1 (ET-1) induces increases in the rate of protein synthesis in a partly pertussis toxin (PTX)-sensitive manner, and that angiotensin II-evoked increases in the rate of protein synthesis are brought about via local secretion of ET-1. The aim of this study was to find out: (1) whether noradrenaline (NA) and the thromboxane A2 (TXA2)-mimetic U 46619-induced increases in the rate of protein synthesis may be also partly PTX-sensitive and/or mediated by ET-1, and (2) whether the growth-promoting effects of NA and U 46619 as well as ET-1 might involve activation of the same set of protein kinase C (PKC) isozymes. For this purpose we first studied the effects of NA and U 46619 on inositol phosphate (IP)-formation (assessed as accumulation of total [3H]IPs in myo-[3H]inositol prelabelled cells) and on the rate of protein synthesis (assessed as [3H]phenylalanine incorporation) (1) in the presence and absence of the ET(A)-receptor antagonist BQ-123, and (2) in nontreated and PTX-pretreated cells. Second, we assessed the effects of the PKC-inhibitors bisindolylmaleimide I and Gö 6976 and of phorbol-12-myristate-13-acetate (PMA; 1 microM overnight)-pretreatment on U 46619-, NA- and ET-1-induced increases in the rate of protein synthesis. NA (0.01-10 microM) concentration-dependently increased IP-formation (maximum increase: 115-/+23% above basal, n=4) and [3H]phenylalanine incorporation (maximum increase: 40+/-3% above basal, n=20). Both responses were antagonized by the alpha1-adrenoceptor antagonist prazosin (1 microM), but were not significantly affected by BQ-123 (1 microM). U 46619 (0.01-100 microM) concentration-dependently increased IP-formation (maximum increase: 89+/-12% above basal, n=8) and [3H]phenylalanine incorporation (maximum increase: 33+/-4% above basal, n=16). Both responses were slightly but significantly antagonized by the TP-receptor antagonist SQ 29548 (1 microM), but were not affected by BQ-123 (1 microM). Pretreatment of the cardiomyocytes with 250 ng ml(-1) PTX overnight did not significantly affect NA- and U 46619-evoked increases in IP-formation and [3H]phenylalanine incorporation. The PKC-inhibitor bisindolylmaleimide I (5 microM) as well as pretreatment of the cells with PMA (1 microM) significantly reduced the effects of NA, U 46619 and ET- I on the rate of protein synthesis; in contrast, the PKC-inhibitor Gö 6976 (5 microM) was without any effects. We conclude that, in rat neonatal ventricular cardiomyocytes, stimulation of Gq/11-coupled receptors increases the rate of protein synthesis; this involves activation of the same PKC-isozymes (very likely PKC-delta and/or -epsilon). NA and U 46619 cause their growth-promoting effects in a PTX-insensitive manner; ET-1 is not involved in their effects.
Pönicke
K
K
Institute of Pharmacology and Toxicology, Martin Luther University of Halle-Wittenberg, Halle, Germany.
Heinroth-Hoffmann
I
I
Becker
K
K
Osten
B
B
Brodde
O E
OE
D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002217:Carbachol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000502:physiology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006834:Hydrazines / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007295:Inositol Phosphates / Q000096:biosynthesis; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000502:physiology; D008301:Maleimides / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D037342:Pertussis Toxin; D010649:Phenylalanine / Q000187:drug effects / Q000378:metabolism; D014176:Protein Biosynthesis; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology; D011506:Proteins / Q000187:drug effects; D051381:Rats; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014316:Tritium; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D000316:Adrenergic alpha-Agonists; D019086:Bridged Bicyclo Compounds, Heterocyclic; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D005231:Fatty Acids, Unsaturated; D006834:Hydrazines; D007211:Indoles; D007295:Inositol Phosphates; D007527:Isoenzymes; D008301:Maleimides; D011506:Proteins; D011956:Receptors, Cell Surface; D010566:Virulence Factors, Bordetella; D014316:Tritium; D010649:Phenylalanine; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; C045749:SQ 29548; D002217:Carbachol; D037342:Pertussis Toxin; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; C070515:bisindolylmaleimide I; D013755:Tetradecanoylphorbol Acetate; D009638:Norepinephrine