Angiotensin II stimulates protein synthesis and inhibits proliferation in primary cultures of rat adrenal glomerulosa cells

Abstract

Angiotensin II (Ang II) is one of the most important stimuli of rat adrenal glomerulosa cells. The aim of the present study was to investigate whether Ang II can stimulate cell proliferation and/or hypertrophy and investigate pathways and intracellular targets. A 3-d treatment with Ang II (5-100 nM), through the Ang II type 1 receptor subtype, abolished cell proliferation observed in control cells but increased protein synthesis. Preincubation with PD98059 (a MAPK kinase inhibitor) abolished basal proliferation and had no effect on basal protein synthesis but did reverse the effect of Ang II on protein synthesis. The p38 MAPK inhibitor SB203580 reversed the inhibitory effect on cell proliferation and abolished the increase in protein synthesis, whereas the c-Jun N-terminal kinase inhibitor SP600125 had no effect. Time-course studies revealed that Ang II stimulated phosphorylation of both p42/p44mapk and p38 MAPK but did not activate c-Jun N-terminal kinase. Ang II had no effect on the level of cyclin E expression but increased the expression of the cyclin-dependent kinase, p27Kip1, an effect abolished in cells preincubated with SB203580 and PD98059. In conclusion, in cultured rat glomerulosa cells, a 3-d treatment with Ang II increases protein synthesis, with a concomitant decrease in proliferation. These effects are mediated by both the p42/p44mapk and p38 MAPK pathways, which increase expression of the steroidogenic enzymes, steroidogenic acute regulatory protein and 3β-hydroxysteroid dehydrogenase and p27Kip1, a protein known to block the cell cycle in G1 phase. Together these results support the key role of Ang II as a stimulus of steroid synthesis rather than a proliferating factor.