Neuroendocrinology. 1990 Sep;52(3):238-42.  

Role of arachidonic acid or its metabolites in growth-hormone-releasing
factor-induced release of somatostatin from the median eminence.

Aguila MC, Milenkovic L, McCann SM, Snyder GD.

Department of Physiology, University of Texas Southwestern Medical Center,
Dallas.

The possible involvement of arachidonic acid (AA) release in
growth-hormone-releasing factor (GRF)-induced somatostatin (SRIF) release from
the median eminence (ME) of the hypothalamus was evaluated in adult male rats
using an in vitro incubation system. The MEs were preincubated with [14C]-AA,
then washed and incubated with vehicle or test agents, and the release of SRIF
and [14C]-AA into the medium was measured. In the experiments designed only to
determine SRIF release, the MEs were first preincubated for 30 min. The medium
was then discarded and replaced with fresh buffer or test substances and
incubated for 10, 20 and/or 30 min. GRF (10(-10) M) stimulated both AA and SRIF
release significantly within 20 min, with maximum release occurring at 30 min.
The stimulatory effect of GRF on AA release was coincident with the release of
SRIF. A phospholipase A2 inhibitor (10(-6) M, quinacrine) completely abolished
the stimulatory effect of GRF on both AA and SRIF release. The release of SRIF
induced by GRF was also inhibited by both indomethacin (10(-6) M, a
cyclooxygenase inhibitor) and metyrapone (10(-6) M, a cytochrome P-450
inhibitor). On the other hand, nordihydroguaiaretic acid (10(-6) M, a
lipoxygenase inhibitor) had no effect on GRF-evoked SRIF release. The data
presented here suggest that an important GRF-mediated event leading to SRIF
secretion is an elevated release of AA from ME fragments in vitro. In
conclusion, our data are suggestive that the stimulatory effect of GRF on SRIF
release is due, in part, to the release and subsequent metabolism of AA to one
or more metabolites.

PMID: 1977095 [PubMed - indexed for MEDLINE]