Patch-Clamp Measurements Reveal Multimodal Distribution of Granule Sizes in Rat Mast Cells

• Published in: The Journal of cell biology 1990-04, Vol.110 (4), p.1033-1039
• Main Authors: de Toledo, Guillermo Alvarez, Fernandez, Julio M.
• Format: Article
• Language: English
• Subjects: Aging; Animals; Biological and medical sciences; Capacitance; Cell Membrane - drug effects; Cell Membrane - physiology; Cell Membrane - ultrastructure; Cell membranes; Cell physiology; Cytoplasmic Granules - physiology; Cytoplasmic Granules - ultrastructure; Electric Conductivity; Electrophysiology - methods; Exocytosis; Fundamental and applied biological sciences. Psychology; Guanosine 5'-O-(3-Thiotriphosphate); Guanosine Triphosphate - analogs & derivatives; Guanosine Triphosphate - pharmacology; Histograms; Kinetics; Mast cells; Mast Cells - physiology; Mast Cells - ultrastructure; Membrane Fusion; Models, Biological; Molecular and cellular biology; P branes; Rats; Rats, Inbred Strains; Secretion. Exocytosis; Secretory cells; Secretory vesicles; Statistical variance; Surface areas; Thionucleotides - pharmacology
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.110.4.1033

Using patch-clamp techniques, we have followed the attributes of the secretory granules of peritoneal mast cells obtained from rats of different ages. The granule attributes were determined by following the step increases in the cell surface membrane area caused by the exocytosis of the granules in GTPγS stimulated mast cells. Our data show that the amount of granule membrane available for exocytosis depends exponentially on the weight (age) of the donor rat, reaching a maximum at ∼300 g. The data are consistent with an exponential growth in the number of granules contained by mast cells of maturing animals. Histograms of the sizes of the step increases in surface area caused by exocytosis of the granules showed at least four equally spaced peaks of similar variance where the position of the first peak and the spacing between peaks averaged 1.3± 0.4 μ m2. In all cells recorded, no more than seven peaks could be found, the higher order peaks having a lower probability of occurrence. The distribution of granule sizes did not change measurably between young and adult animals. This study suggests that at least two separate steps may determine the size of a secretory granule: granule to granule fusion that may account for the subunit composition of granule sizes and traffic of microvesicles through the maturing granules that may account for the variance observed in the granule sizes. This study also demonstrates a novel way to study granulogenesis in living cells.