Synergistic actions of epidermal growth factor-urogastrone and vasopressin in cultured aortic A-10 smooth muscle cells.
In cultured rat aorta-derived A-10 cells, epidermal growth factor-urogastrone (EGF-URO) acts synergistically with arginine vasopressin (AVP) to augment the AVP-mediated release of 3H-arachidonate (3H-AA) from 3H-AA prelabeled cells. On its own, EGF-URO had no effect on AA release and had no effect on calcium influx or efflux either in the absence or presence of AVP. The synergistic action of EGF-URO was not affected by actinomycin D, cycloheximide, indomethacin, by the diacylglycerol lipase inhibitor U-57,908, or by the tyrosine kinase inhibitors genistein (GS) and tyrphostin (TP). TP did, nonetheless, completely abrogate 3H-thymidine incorporation triggered in the presence of EGF-URO. Although EGF-URO stimulated an increase in calpactin-II (lipocortin-I) phosphorylation in permeabilized cells, no such increase was detected in intact cells exposed to EGF-URO either alone or in combination with AVP, under conditions where EGF-URO augmented the action of AVP. The phospholipase A2 inhibitor, mepacrine, had no effect on AVP-mediated AA release, but abolished the synergistic action of EGF-URO. We conclude that in contrast with our previous results with gastric smooth muscle strips, wherein EGF-URO acts via the diacylglycerol lipase-mediated metabolism of diacylglycerol, and in keeping with observations with cultured mesangial cells, EGF-URO acts synergistically with AVP in A-10 cells via the activation of phospholipase A2. This synergistic action of EGF-URO does not appear to be due to increased levels of cyclooxygenase and would appear not to require increased tyrosine kinase activity.
Mokashi
S
S
Department of Pharmacology and Therapeutics, University of Calgary, Faculty of Medicine, Alberta, Canada.
Severson
D L
DL
Hollenberg
M D
MD
D000818:Animals; D017302:Annexins; D001011:Aorta / Q000166:cytology / Q000378:metabolism*; D016718:Arachidonic Acid / Q000378:metabolism; D001127:Arginine Vasopressin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002396:Catechols / Q000494:pharmacology; D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D004357:Drug Synergism; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D013997:Time Factors; D020032:Tyrphostins
D017302:Annexins; D002135:Calcium-Binding Proteins; D002396:Catechols; D009570:Nitriles; D020032:Tyrphostins; D001127:Arginine Vasopressin; C060152:tyrphostin 47; D003609:Dactinomycin; D016718:Arachidonic Acid; D004815:Epidermal Growth Factor; D003513:Cycloheximide; D011505:Protein-Tyrosine Kinases; D002118:Calcium