Src family kinase involvement in rat preglomerular microvascular contractile and [Ca ]i responses to ANG II

Che, Qi, and Pamela K. Carmines. Src family kinase involvement in rat preglomerular microvascular contractile and [Ca ]i responses to ANG II. Am J Physiol Renal Physiol 288: F658–F664, 2005. First published November 30, 2004; doi:10.1152/ajprenal. 00392.2004.—Experiments were performed to investigate the potential role of Src family kinase(s) in the rat afferent arteriolar contractile response to ANG II. The in vitro blood-perfused juxtamedullary nephron technique was employed to monitor afferent arteriolar lumen diameter responses to 1–100 nM ANG II before and during Src family kinase inhibition (10 M PP2). PP2 did not alter baseline diameter but attenuated ANG II-induced contractile responses by 33 6%. An inactive analog of PP2 (PP3) had no effect on ANG II-induced afferent arteriolar contraction. The effect of Src kinase inhibition on ANG II-induced intracellular free Ca concentration ([Ca ]i) responses was probed in fura 2-loaded preglomerular microvascular smooth muscle cells (PVSMCs) obtained from explants and studied after 3–5 days in culture. In untreated PVSMCs, ANG II evoked peak ( 293 66 nM) and plateau ( 23 8 nM) increases in [Ca ]i. In PVSMCs pretreated with PP2, baseline [Ca ]i was unaltered, but both the peak ( 140 22 nM) and plateau ( 3 2 nM) phases of the ANG II response were significantly reduced compared with untreated cells. PP3 did not alter [Ca ]i responses to ANG II. Immunoprecipitation and Western blot analysis confirmed that 100 nM ANG II increased phosphorylation of c-Src (at Y) in PVSMCs. The phosphorylation response was maximal 1 min after ANG II exposure and was prevented by PP2. We conclude that the preglomerular vasoconstriction evoked by ANG II involves rapid c-Src activation with subsequent effects that contribute to the [Ca ]i response to the peptide.