GENISTEIN INHIBITS NA+ CA2+ EXCHANGE ACTIVITY IN PRIMARY RAT CORTICALNEURON CULTURE/

We have examined the possible regulatory effect of tyrosine kinase act ivity on Ca2+ transport observed in the cultured rat cortical neurons, Na+/Ca2+ exchange was studied using cells cultured for various time p eriods. A nearly two fold increase in Ca2+ uptake was seen when compar ing 3 day and 9 day cultures. Western blot analysis also showed a two fold increase in Na+/Ca2+ exchanger (NCX1) protein levels as cells mat ured in culture, To study the effect of genistein (a specific tyrosine kinase inhibitor) cells were incubated with 100 mu M genistein (in 1% DMSO) for 1 hour before the assay of Na+/Ca2+ exchange activity, Ther e was a significant decrease of Ca2+ uptake in genistein treated neuro ns (control: 4.596+/-0.205 nmol/mg protein/15min, n=12; genistein: 1.4 20+/-0.131 nmol/mg protein/15min, n=12, mean+/-S.E. P<0.001). Daidzein , an inactive analog of genistein and phorbol myristate acetate (PMA), a PKC activator were without effect, The results suggest that as cell s mature in culture, Na+/Ca2+ exchange capacity increases, as a result of greater protein expression, Exposure to genistein inhibited Ca2+ u ptake suggesting that the exchanger may be modulated by tyrosine phosp horylation. (C) 1997 Academic Press.