Enhanced vasoactive intestinal peptide-induced prolactin secretion from anterior pituitary cells of incubating turkeys (Meleagris gallopavo)

ABSTRACT Bradykinin stimulated prolactin secretion from monolayer cultures of rat anterior pituitary cells, the stimulation being greater from the cells of male rats. This stimulated secretion was accompanied by a rise in total inositol phosphate accumulation, suggesting that the action of bradykinin is mediated by phosphoinositide hydrolysis. The increase in inositol phosphate accumulation was biphasic; a further sharp rise occurred when the concentration of bradykinin exceeded 1 μmol/l. This may indicate that bradykinin acts on other cell types in the pituitary gland. Bradykinin had no effect on growth hormone secretion from cells of normal pituitary glands, or on prolactin secretion and phosphoinositide metabolism in GH3 rat pituitary tumour cells. Bradykinin receptor antagonists (both B1 and B2) had no effect on either bradykinin-stimulated inositol phosphate accumulation or prolactin secretion. Kallikreins, the enzymes responsible for the generation of kinins, are known to be present in the adenohypophysis. Therefore, the results presented here would suggest that kinins may have a role as paracrine agents in the pituitary gland.

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Use of a fluorescent dye to measure secretion from intact bovine anterior pituitary cells

Bioscience Reports ◽

10.1007/bf01138174 ◽

1993 ◽

Vol 13 (1) ◽

pp. 9-17 ◽

Cited By ~ 7

Author(s):

Sarah J. V. Stafford ◽

Spencer L. Shorte ◽

J. George Schofield

Keyword(s):

Anterior Pituitary ◽

Dopamine D2 Receptor ◽

D2 Receptor ◽

Secretory Vesicle ◽

Prolactin Secretion ◽

Fluorescent Dye ◽

Pituitary Cells ◽

Anterior Pituitary Cells ◽

Trh Stimulation ◽

Membrane Changes

The fluorescent dye FM1-43 has been used to indicate membrane changes in individual bovine anterior pituitary cells exposed to secretory stimuli. After ten minutes incubation with FM1-43 (2 μM), cells showed three patterns of dye fluorescence: annular, partly filled and uniformly filled. FM1-43 fluorescence was increased in 61% of the cells by TRH (40 nM), a physiological stimulus for prolactin secretion, and in 89% of the cells by 60 mM external K+. The fluorescence also increased when cells incubated in the presence of quinpirole, a dopamine D2-receptor agonist which inhibits prolactin secretion, were exposed to raclopride, a D-2 antagonist. The increases in FM1-43 fluorescence caused by these treatments suggests that the dye acts as an indicator of secretion, possibly through incorporation into secretory vesicle membranes exposed on the cell surface during exocytosis. If the dye was washed away after loading, the fluorescence of partly and uniformly filled cells was retained and a rise in fluorescence could still be seen on stimulation by TRH. This suggests that some dye had been taken up by endocytosis and trapped in an intracellular compartment, which expanded through membrane recapture after TRH stimulation. FM1-43 could therefore be a useful probe for membrane cycling associated with secretory responses.

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