TY - JOUR T1 - <em>Alpha</em>-1A Adrenergic Receptor Stimulation with Phenylephrine Promotes Arachidonic Acid Release by Activation of Phospholipase D in Rat-1 Fibroblasts: Inhibition by Protein Kinase A JF - Journal of Pharmacology and Experimental Therapeutics JO - J Pharmacol Exp Ther SP - 576 LP - 585 VL - 284 IS - 2 AU - Ying Ruan AU - Hong Kan AU - Jean-Hugues Parmentier AU - Soghra Fatima AU - Lee F. Allen AU - Kafait U. Malik Y1 - 1998/02/01 UR - http://jpet.aspetjournals.org/content/284/2/576.abstract N2 - This study was conducted to determine the mechanism of arachidonic acid (AA) release elicited by phenylephrine (PHE) stimulation ofalpha adrenergic receptor (AR), and its modulation by cyclic adenosine 3′,5′-monophosphate (cAMP) in Rat-1 fibroblasts (R-1Fs) transfected with the alpha-1A,alpha-1B or alpha-1D AR. PHE increased AA release and also caused a marked accumulation of cAMP in R-1Fs expressing the alpha-1 AR subtypes, but not in those transfected with vector alone. PHE also enhanced phospholipase D (PLD), but not phospholipase A2 (PLA2) activity. The increase in PHE-induced AA release, PLD activity and cAMP accumulation differed among the various alpha AR subtypes with: alpha-1A &gt;alpha-1B &gt; alpha-1D AR. The effect of PHE to increase AA release was attenuated by C2-ceramide, an inhibitor of PLD; propranolol, a phosphatidate phosphohydrolase inhibitor; and RHC-80267, a diacylglycerol lipase inhibitor in R-1Fs expressing thealpha-1A AR. Forskolin, which activates adenylyl cyclase, increased cAMP accumulation and inhibited PHE-induced AA release and PLD activity in alpha-1A-AR–expressing R-1Fs. 8-(4-chlorophenyl-thio)-cAMP, a nonhydrolyzable analog of cAMP, also attenuated the rise in AA release and PLD activity elicited by PHE in these cells. In contrast, SQ 22536, an adenylyl cyclase inhibitor, and KT 5720, a protein kinase A inhibitor, increased PHE-induced AA release and PLD activity in R-1Fs expressing thealpha-1A AR. These data suggest that thealpha-1A, alpha-1B andalpha-1D ARs are coupled to PLD activation and cAMP accumulation. Moreover, PHE promotes AA release in R-1Fs expressing thealpha-1A AR through PLD activation. Furthermore, cAMP generated by alpha-1A AR stimulation acts as an inhibitory modulator of PLD activity and AA release viaprotein kinase A. The American Society for Pharmacology and Experimental Therapeutics ER -