Angiotensin II (ANG II) has a biphasic effect on Na⁢ transport in proximal tubule: low doses of ANG II increase the Na⁢ transport, whereas high doses of ANG II inhibit it. However, the mechanisms of high dose ANG II-induced inhibition on Na⁢ uptake are poorly understood. Thus the aim of the present study was to investigate signal transduction pathways involved in the ANG II-induced inhibition of Na⁢ uptake in the primary cultured rabbit renal proximal tubule cells (PTCs) in hormonally defined serum-free medium. ANG II (10⁣9 M)-induced inhibition of Na⁢ uptake was blocked by losartan (10⁣8 M, AT1 antagonist), but not by PD123319 (10⁣8 M, AT2 antagonist) (P＜0.05). ANG II-induced inhibition of Na⁢ uptake was also completely abolished by neomycin (10⁣4 M, PLC inhibitor), W-7 (10⁣4 M, calmodulin antagonist), and AACOCF3 (10⁣6 M, PLA2 inhibitor) (P＜0.05). ANG II significantly increased [3H]arachidonic acid (AA) release compared to control. The ANG II-induced [3H]AA release was blocked by losartan, AACOCF3, neomycin, and W-7, but not by PD123319. ANG II-induced [3H]AA release in the presence of extracellular Ca2⁢ was greater than in Ca2⁢-free medium, and it was partially blocked by TMB-8 (10⁣4 M, intracelluar Ca2⁢ mobilization blocker). However, in the absence of extracellular Ca2⁢, it was completely blocked by TMB-8. In addition, econazole (10⁣6 M, cytochrome P-450 monooxygenase inhibitor) and indomethacin (10⁣6 M, cyclooxygenase inhibitor) blocked ANG II-induced inhibition of Na⁢ uptake, but NGDA (10⁣6 M, lipoxygenase inhibitor) did not affect it. In conclusion, PLA2-mediated AA release is involved in ANG II-induced inhibition of Na⁢ uptake and is modulated by [Ca2⁢]i in the PTCs.