EVIDENCE THAT THE POSTERIOR PITUITARY PLAYS A ROLE IN NEUROPEPTIDE-Y AND LUTEINIZING-HORMONE-RELEASING HORMONE-STIMULATED GONADOTROPIN-SECRETION IN-VITRO
Jl. Oconner et Mf. Wade, EVIDENCE THAT THE POSTERIOR PITUITARY PLAYS A ROLE IN NEUROPEPTIDE-Y AND LUTEINIZING-HORMONE-RELEASING HORMONE-STIMULATED GONADOTROPIN-SECRETION IN-VITRO, Proceedings of the Society for Experimental Biology and Medicine, 213(1), 1996, pp. 59-64
Neuropeptide Y (NPY) has been shown to increase gonadotropin secretion
directly at the level of the anterior pituitary (AP) in both the abse
nce and the presence of luteinizing hormone-releasing hormone (LHRH).
This is interesting because high-affinity I-125-NPY-binding sites have
not been found in the AP. However, high-affinity I-125-NPY-binding si
tes have been localized in the posterior pituitary (PP), and it has be
en shown that removal of the PP alters luteinizing hormone (LH) secret
ion in vivo, The following studies were conducted to determine if gona
dotropin responsiveness to either NPY alone or to NPY in combination w
ith LHRH was significantly different in AP cells cultured in the prese
nce compared with the absence of PP cells. The studies indicated that
NPY-induced LH secretion was significantly greater in the presence of
PP cells, while follicle-stimulating hormone (FSH) secretion was not s
ignificantly affected. LHRH-induced LH secretion was also significantl
y greater in the presence of PP cells; however, LHRH-induced FSH secre
tion was significantly decreased. NPY potentiated LHRH-induced LH secr
etion in AP cells cultured in both the presence and the absence of PP
cells; however, the degree of potentiation was not significantly diffe
rent whether PP cells were present or absent. These results indicate t
hat the PP may play a role in the responsiveness of the AP to NPY and
to LHRH but plays no apparent role in NPY potentiation of LHRH respons
iveness.