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Microinjection of macromolecules into living cells has proved to be a powerful technique for the functional analysis of gene products in living somatic cells. This approach is useful for the introduction of functional proteins, genes, inhibitors of enzyme activities and antibodies into living cells (Ansorge, 1982). Types of cells into which these molecules can be introduced include primary and established cell lines, fibroblasts and cells of various tissue types, including contractile cardiac cells. Some of the advantages of microinjection over other methods of introducing biological materials into cells (Celis, 1984; Graessmann et al., 1980; Pepperkok et al., 1988) are as follows: (1) Economy of the material; microinjection delivers small volumes (10−13-10−15 1) directly into specific cells which means that the amount of material needed is much less than would be required for other approaches (e.g., scrape loading). (2) Damage to the cell appears to be much less than with other methods as evidence by stress responses, etc. (3) There is much less limitation on the nature of the material injected; for example, nucleic acids, proteins, large and small molecules can all be introduced with little alteration of the technique. (4) Temporal experiments can be performed where the response at a given time to a particular reagent may be monitored. Also, two or more different proteins may be introduced consequently in a defined order into the cell by re-injecting the same cell more than once. It is not easy to do this by other approaches such as transfection. (5) Molecules which had been altered in vitro may be injected in order to determine the effect of post-translational modifications. (6) Direct comparison of the effect of the injected material may be made by comparing injected and uninjected cells or cells injected with control material on the same dish. |
