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The role of prostaglandin E2 and other eicosanoids in catecholamine secretion from adrenal chromaffin cells /

McGill University
Publication Date
  • Biology
  • General.
  • Biology


Prostaglandins E$ sb1$ and E$ sb1$ are bound with high affinity and specificity to particulate fractions from bovine, ovine and human adrenal medulla. An identical fraction from fetal bovine and ovine adrenals binds PGEs with similar kinetic properties and specificities. The ${ rm lbrack sp3H rbrack}$PGE$ sb2$-binding site complex dissociates in a biphasic manner, suggesting the presence of both a low and high affinity form of the complex. Gpp(NH)p, a stable GTP analogue, inhibits PGE$ sb2$ binding by promoting the conversion of the high affinity form of the complex to the lower affinity state. In subcellular fractionation studies, PGE$ sb2$ binding sites co-purity with acetylcholinesterase and Ca$ sp{2+}$-ATPase activities (marker enzymes for the chromaffin cell plasma membrane). Bovine adrenal medullary cells in culture, prelabeled with ${ rm lbrack sp3H rbrack}$arachidonic acid, metabolize the precursor fatty acid to PGE$ sb2,$ 6-oxoPGF$ sb{1 alpha}$ and other unidentified products, when stimulated with the calcium-ionophore A23187. PGE$ sb2$ (10$ sp{-9}$ M) inhibits both nicotine and high K$ sp+$-induced catecholamine secretion from chromaffin cells by a mechanism unrelated to alterations in intracellular levels of cyclic nucleotides. LTC$ sb4$ and LTB$ sb4$ stimulate spontaneous catecholamine release but this effect is not always reproducible. NDGA attenuates nicotine-induced secretion, while indomethacin has no effect. These data suggest that the inhibitory effect of PGE$ sp2$ on chromaffin cell secretion is initiated by the release of the prostaglandin during cellular activation, followed by the binding of PGE$ sb2$ to its receptor and the subsequent interaction of this complex with a guanine nucleotide-binding protein.

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