AJP - Lung Cellular and Molecular Physiology, Vol 263, Issue 2 168-L176, Copyright © 1992 by American Physiological Society
Prostaglandin D2 production and identification of prostaglandin H synthase within canine mast cell granule
P. S. Thomas, A. N. Wilson, R. E. Schreck and S. C. Lazarus
Cardiovascular Research Institute, University of California, San Francisco 94143.
We have identified the presence of functional prostaglandin H synthase (PGH
synthase, E.C. 1.14.99.1, or cyclooxygenase) within canine mast cell
granules by demonstrating the generation of prostaglandin (PG) D2 from
isolated and purified granules incubated with substrate as arachidonic acid
or stimulated with calcium ionophore, A23187. This confirms the presence of
both enzyme and substrate within the granule. Localization of PGH synthase
to the granule was confirmed by immunoblotting of the pure granule
preparation and by immunocytochemistry using the whole cell. In functional
studies, colchicine, a microtubule polymerization inhibitor, caused a fall
of up to 70%, both in the amount of histamine released and in the amount of
PGD2 generated. This suggests either that functional PGH synthase is
closely associated and coactivated with granules or that there is an
independent association of this enzyme with the microtubule system. Release
of the preformed and newly formed mediators of the mast cell appear to be
closely linked, and prevention of degranulation may therefore attenuate the
effects of both classes of mediators.
