A preferential pole for exocytosis in cultured chromaffin cells revealed by confocal microscopy

Histological studies suggest that adrenal medulla chromaffin cells in situ are polarised, but functional evidence is lacking. We present here the firs t demonstration for polarisation of exocytosis in isolated, spherical, bovi ne chromaffin cells. Cells were stimulated with 70 mM K+ to cause a marked enhancement of catecholamine release, monitored amperometrically. FM1-43 an d dopamine beta-hydroxylase antibodies provided fluorescence confocal pictu res that were 2-3-fold more intense in the bottom of the cells, as compared to equatorial or apex plants. This suggests that the solid phase to which the cell attaches serves as a 'trophic' signal for the polarisation of its secretory apparatus. (C) 1999 Federation of European Biochemical Societies.