Electrical and Pharmacological Properties of Freshly Isolated Single Smooth Muscle Cells

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The long term goals of this research program are to understand the function of ionic channels in the membrane of smooth muscle cells and their regulation by transmitters, ions, metabolites, second messengers, and membrane potential. Since ionic channels control the membrane potential, serve as one of the principal targets of neurotronsmitters and second messenger mechanisms, underlie the action potential, and govern calcium entry into the cell, they play a central role in the regulation of smooth muscle contraction. The experiments employ freshly dissociated cells from the stomach of the bullfrog, Bufo marinus. Emphasis will be placed on patch-clamp techniques to record both whole-cell and single-channel currents. The specific goals for which support is requested are studies of the mechanism of potassium channel activation by arachidonic acid and related fatty acids which has been observed in preliminary experiments. Studies will will be carried out to determine whether potassium channel activaton is caused by arachidonic acid and other fatty acids themselves or by metabolites derived from these fatty acids. A variety of compounds structurally related to arachidonic acid and other fatty acids will be examined to establish which structural features are required for the molecules to be effective in inducing potassium current. Possible endogenous agents that may be releasing the fatty acids will be sought and identified, and any additional effects of fatty acids on channels will be studied. The role of arachidonic acid and other fatty acids as second messengers in transmission of external signals to the biochemical machinery within cells has recently become the focus of attention in a number of cell systems. The preliminary observations of Drs. Singer and Walsh that these agents appear to affect ion channels in the membranes of smooth muscle cells suggest a previously unexpected mechanism by which the excitability and contractile activity of these cells may be modulated. The further analysis of these new observations may lead to important insights into the mechanisms of regulation of contraction of smooth muscle, and more generally into the mechanisms by which the permeability of cell membranes is regulated.