The swelling of astroglial cells is a major factor in the cytotoxic edema which follows head trauma and cerebral ischemia and hypoxia. The long term goals of this project are to increase our understanding of the mechanisms regulating astroglial volume, to delineate the factors responsible for the swelling caused by brain insult, and to test, in vitro, methods of preventing that swelling based on knowledge of the underlying mechanisms. For these studies we will use a newly developed continuous cell line, UC-11, derived from a human astrocytoma. A detailed characterization of the astroglial-like properties of the UC-11 cells has recently been completed. We have found that these cells produce glial fibrillary acidic protein, a specific atroglial marker, and that, in the presence of dibutyryl cAMP, they can be induced to form the elongated processes typical of astroglial morphology. UC-11 cells also exhibit the large electrical membrane potentials in the absence of any ability to generate an action potential that constitutes another unusual feature of astroglia. Biochemically, these cells also resemble normal astrocytes in their high levels of glutamine synthetase and in the production of S-100 protein. Thus, the UC-11 cells now constitute a uniquely well-characterized, continuous line of human cells with a broad range astrocytic properties. In the first stage of the project, conditions which have been postulated to underlie in vivo astroglial swelling will be tested in the UC-11 system in vitro. These parameters include elevated extracellular K+, hypoglycemia, hypercarbia, hypoxia, increased concentrations of neurotransmitters, and serum factors. We will determine the effects of these agents on cell swelling and on the transport of the monovalent anions and cations which is known to regulate water movement. The second stage of the work will involve studies of inhibitors of ion transport which may help to elucidate the specific pathways of astroglial ion movements and which are also of potential therapeutic value in the control of astroglial swelling. This will include specific C1-exchange transport inhibitors, NaC1/KC1 cotransport inhibitors, carbonic anhydrase inhibitors, and inhibitors of neurotransmitter action. Among these pharmacological agents are some compounds which have already been shown to be of value in the treatment of brain edema. In this way we hope to develop a model system for defining the in vivo agents which cause astroglial swelling, to elucidate the mechanisms by which swelling occurs, and to test the responses of astroglia to potential therapeutic agents.
