AJP - Cell Physiology, Vol 257, Issue 6 C1166-C1170, Copyright © 1989 by American Physiological Society
In vitro adsorption losses of arachidonic acid and calcium ionophore A23187
D. R. Samples, E. A. Sprague, M. J. Harper and J. T. Herlihy
Department of Physiology, University of Texas Health Science Center, San Antonio 78284.
Arachidonic acid (AA) is often utilized in in vitro studies to label
cellular pools of AA or to elicit cellular responses dependent on
eicosanoid production. Because of the hydrophobic nature of AA, organic
diluents such as ethanol or dimethyl sulfoxide are utilized in preparing
concentrated solutions. The fate of AA when added to aqueous medium is not
generally considered because of the dilution of the AA, although some
investigators utilize bovine serum albumin (BSA) to solubilize as well as
to trap AA and its hydrophobic metabolites. These experiments demonstrate a
rapid and progressive decline in AA concentration when added to aqueous
media in tissue baths and in glass test tubes. The extent of the decline
was greater in the tissue baths than in the test tubes. The calcium
ionophore A23187, which is used to stimulate AA metabolism, is also
hydrophobic, and its concentration also decreased when added to aqueous
media. The decline in the concentration of both AA and A23187 was due to
adsorption to the container walls. The presence of 1% BSA in the aqueous
solution attenuated and even eliminated the decline in the concentration,
indicating binding of the two agents to the protein. However, the presence
of BSA in culture medium inhibited the A23187-induced stimulation of AA
metabolites in baboon aortic smooth muscle cells. These results underscore
the complexities arising from the in vitro use of hydrophobic substances in
biological systems.
