Angiotensin-II Stimulates DNA Synthesis in rat adrenal zona glomerulosa cells: Receptor subtypes involved and possible signal transduction mechanism

Using an in situ perfusion technique of isolated left rat adrenal gland, it has been demonstrated that angiotensin-II (ANG-II) increases DNA synthesis in the zona glomerulosa (ZG), but not fasciculata-reticularis cells. The AT1 receptor antagonist DuP753 abolished the effect of ANG-II, while the AT2 receptor antagonist PD 123319 potentiated it. Both Ro31-8220, an inhibitor of protein kinase C (PKC), and tyrphostin-23, an inhibitor of tyrosine kinase (TK), evoked a partial reversal of ANG-II effect, and when added together to the perfusion medium abolished it. In contrast, the phospholipase C inhibitor U-73122 alone was able to induce a complete blockade of ANG-II effect. Neither the phospholipase A2 inhibitor AACOCF3 nor the cyclooxygenase inhibitor indomethacin and the lipoxygenase inhibitor phenidone affected ANG-II-induced stimulation of DNA synthesis, thereby making unlikely the involvement of the arachidonic acid signaling pathways. Our findings suggest that (i) ANG-II stimulates rat ZG cell proliferation acting via AT1 receptors coupled with phospholipase C, which activates both PKC and TK signaling systems; and (ii) the proliferogenic effect of ANG-II is partially counteracted by the activation of the AT2 receptor subtype.