Modulation of the (Na+ + K+)ATPase activity by Angiotensin-(1–7) in MDCK cells

Abstract In the present paper the effect of Ang-(1–7) on the distal tubule (Na +  + K + )ATPase activity was evaluated by using MDCK cells as a model. Confluent cell monolayers were incubated with increasing concentrations of Ang-(1–7) for 30 min. Thereafter, the (Na +  + K + )ATPase activity was evaluated and a dose–dependent (from 10 −12 to 10 −7 M) inhibition was observed. The maximal inhibitory effect (54%) was reached at the concentration of 10 −8 M. The inhibitory effect of Ang-(1–7) was not affected by the AT 2 receptor selective antagonist PD123319 (from 10 −10 to 10 −7 M) but was blocked in a dose–dependent manner by the AT 1 receptor selective antagonists losartan (10 −10 M), candesartan (10 −17 M), irbesartan (2 × 10 −12 M) and telmisartan (2 × 10 −16 M). The signaling pathway triggered by stimulation of the AT 1 receptor was also investigated. The PI-phospholipase C (PI-PLC) inhibitor U73122 (5 × 10 −8 M) blocked the inhibitory effect elicited by Ang-(1–7). Involvement of the protein kinase C (PKC) was evidenced by the sensitivity of the inhibitory effect of Ang-(1–7) to calphostin C (6.32 × 10 −7 M) and the lack of additive effects when the cells were co-incubated with Ang-(1–7) and 3.2 × 10 −8 M PMA. Altogether, these results demonstrate that Ang-(1–7) inhibits the (Na +  + K + )ATPase activity of the prototypic distal tubule cell MDCK through the AT 1 receptor-mediated stimulation of PI-PLC/PKC signaling pathway.