A Signaling Pathway for Stimulation of Na+ Uptake Induced by Angiotensin II in Primary Cultured Rabbit Renal Proximal Tubule Cells
Journal of Veterinary Medical Science
The aim of the present study was to examine the signaling pathways for a low dose of angiotensin II (ANG II) on Na + uptake of primary cultured rabbit renal proximal tubule cells (PTCs) in hormonally defined serum-free medium. The results were as follows; ANG II (10 11 M) stimulated the proliferation of PTCs. 10 11 M ANG II stimulated Na + uptake by 20%, whereas 10 9 M ANG II inhibited it by 20% (p<0.05). The stimulatory effect of 10 11 M ANG II on Na + uptake was inhibited by amiloride (10 3
... y amiloride (10 3 M) and by losartan (ANG II receptor subtype 1 antagonist, 10 8 M) but not by PD123319 (ANG II receptor subtype 2 antagonist, 10 8 M). Pertussis toxin (PTX, 50 ng/ml) prevented the ANG II-induced stimulation of Na + uptake (p<0.01). 8-Bromoadenosine 3', 5'-cyclic monophosphate (8-Br-cAMP, 10 6 M) did not affect Na + uptake. SQ 22536 (adenylate cyclase inhibitor, 10 6 M) also did not change the ANG II-induced stimulation of Na + uptake. ANG II did not stimulate cAMP production. In contrast, 12-O-tetradecanoylphorbol-13-acetate (TPA, 0.01 ng/ml) produced significant increase in Na + uptake. When ANG II and TPA were added together to the PTCs, there was no additive effect on Na + uptake. Staurosporine (calcium-dependant protein kinase C inhibitor, 10 6 M) led to a complete inhibition of ANG II-induced stimulation of Na + uptake. ANG II-treatment resulted in a 26% increase in total protein kinase C (PKC) activity. However, 10 11 M ANG II did not change [Ca 2+ ] i mobilization and [ 3 H]-AA release while 10 9 M ANG II increased both of them. In conclusion, the PTX-sensitive PKC pathway may be the main signaling cascade in the stimulatory effects of low dose of ANG II (10 11 M) on Na + uptake in the primary cultured rabbit renal proximal tubule cells in hormonally defined serum-free medium.-KEY WORDS: angiotensin II, Na + /H + antiport, primary proximal tubule cell, protein kinase C.