Nongenomic inhibition of catecholamine secretion by 17beta-estradiol in PC12 cells

We investigated the effects of 17beta-estradiol, an estrogen, on [(3)H]norepinephrine ([(3)H]NE) secretion in PC12 cells. Pretreatment with 17beta-estradiol reduced 70 mM K(+)-induced [(3)H]NE secretion in a concentration-dependent manner with a half-maximal inhibitory concentration (IC(50)) of 2 +/- 1 microM. The 70 mM K(+)-induced cytosolic free Ca(2+) concentration ([Ca(2+)](i)) rise was also reduced when the cells were treated with 17beta-estradiol (IC(50) = 15 +/- 2 microM). Studies with voltage-sensitive calcium channel (VSCC) antagonists such as nifedipine and omega-conotoxin GVIA revealed that both L- and N-type VSCCs were affected by 17beta-estradiol treatment. The 17beta-estradiol effect was not changed by pretreatment of the cells with actinomycin D and cycloheximide for 5 h. In addition, treatment with pertussis or cholera toxin did not affect the inhibitory effect of 17beta-estradiol. 17beta-Estradiol also inhibited the ATP-induced [(3)H]NE secretion and [Ca(2+)](i) rise. In PC12 cells, the ATP-induced [Ca(2+)](i) rise is known to occur through P2X(2) receptors, the P2Y(2)-mediated phospholipase C (PLC) pathway, and VSCCs. 17beta-Estradiol pretreatment during complete inhibition of the PLC pathway and VSCCs inhibited the ATP-induced [Ca(2+)](i) rise. Our results suggest that 17beta-estradiol inhibits catecholamine secretion by inhibiting L- and N-type Ca(2+) channels and P2X(2) receptors in a nongenomic manner.