title: Adipocyte cell size enlargement involves plasma membrane area increase.
abstract: The adipocyte enlargement is associated with an increase in the cytoplasmic lipid content, but how the plasma membrane area follows this increase is poorly understood. We monitored single-cell membrane surface area fluctuations, which mirror the dynamics of exocytosis and endocytosis. We employed the patch-clamp technique to measure membrane capacitance (C(m)), a parameter linearly related to the plasma membrane area. Specifically, we studied whether insulin affects membrane area dynamics in adipocytes. A five-minute cell exposure to insulin increased resting C(m) by 12 ± 4%; in controls the change in C(m) was not different from zero. We measured cell diameter of isolated rat adipocytes microscopically. Twenty-four hour exposure of cells to insulin resulted in a significant increase in cell diameter by 5.1 ± 0.6%. We conclude that insulin induces membrane area increase, which may in chronic hyperinsulinemia promote the enlargement of plasma membrane area, acting in concert with other insulin-mediated metabolic effects on adipocytes.
authors.affiliation: Laboratory of Neuroendocrinology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia.
authors.forename: H H
authors.initials: HH
authors.lastname: Chowdhury
authors.forename: R
authors.initials: R
authors.lastname: Zorec
mesh_terms: D017667:Adipocytes / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D049108:Cell Enlargement / Q000187:drug effects*; D002462:Cell Membrane / Q000187:drug effects*; D048429:Cell Size; D002478:Cells, Cultured; D025802:Electric Capacitance; D004705:Endocytosis / Q000502:physiology; D005089:Exocytosis / Q000502:physiology; D007328:Insulin / Q000494:pharmacology*; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D059010:Single-Cell Analysis
chemical_list: D007328:Insulin