Angiotensin II signaling to phospholipase D in renal microvascular smooth muscle cells in SHR

Angiotensin II (Ang II)-induced phospholipase D (PLD) activity is greater i n aortic smooth muscle from spontaneously hypertensive rats (SHR) versus no rmotensive Wistar-Kyoto rats (WKY). Whether and how this signaling pathway is altered in preglomerular microvascular smooth muscle cells (PGSMCs), a c ell type that may participate in genetic hypertension, is unknown. The goal s of the present study were to determine in SHR and WKY PGSMCs the followin g: (1) whether Ang II induces PLD activity; (2) whether the effect of Ang I I on PLD activity is greater in SHR; (3) which PLD isoform is stimulated by Ang II; (4) what signaling pathway mediates Ang II-induced PLD stimulation ; and (5) whether the signaling pathways mediating Ang II-induced PLD activ ity are different in SHR and WKY. The EC50 for Ang II-induced PLD stimulati on in SHR was 10-fold lower than the EC50 in WKY, and both were inhibited b y L-158,805, an AT(1) antagonist. Inhibitors of phosphoinositol-3-kinase an d protein kinase C did not block Ang II-induced PLD activity in SHR and WKY PGSMCs. Catalytically-inactive constructs of PLD2 and RhoA, but not PLD1, ADP ribosylation factor 1 (ARF1), ARF6, or ADP ribosylation factor nucleoti de exchange factor (ARNO) blocked Ang II-induced PLD activity in SHR and WK Y PGSMCs. Brefeldin A completely blocked Ang II-induced PLD activity in SHR but only slightly reduced Ang II-induced PLD activity in WKY PGSMCs. There fore, we conclude that in PGSMCs, the effect of Ang II on PLD activity is ( 1) greater in SHR; (2) mediated by AT(1) receptors signaling to PLD2; (3) t ransduced primarily by Rho proteins; and (4) inhibited in SHR by brefeldin A.