Measurement of Changes in Membrane Surface Morphology Associated with Exocytosis Using Scanning Ion Conductance Microscopy

¹ Univ. of Missouri, Columbia

^* To whom correspondence should be addressed. E-mail: gillisk{at}missouri.edu.

Submitted on May 5, 2006
Revised on May 31, 2006
Accepted on 3 July 2006

	Abstract

The extent that vesicles maintain a distinct identity and morphology after fusing with the plasma membrane is controversial. We used Scanning Ion Conductance Microscopy (SICM) to image changes in the surface membrane of adrenal chromaffin cells following stimulation of exocytosis with a high K⁺ solution. Within several minutes after stimulation, punctuate depressions, 100-600 nm wide, were noted from 16% of the cells. The depressions were not randomly distributed, but appeared in clusters of 2 or more within a ~1 µm² area and disappeared after several minutes. Increases in membrane surface area, consistent with the fusion and collapse of 1 or more vesicles into the surface membrane, were observed in 64% of the cells following high K⁺ stimulation. Surface area increases did not occur if the high K⁺ solution did not contain Ca²⁺. We conclude that SICM can be used to follow the time course of surface membrane changes resulting from exocytosis and endocytosis.

Key Words: chromaffin cells, endocytosis