Annexin 5 inhibits thyrotropin releasing hormone (TRH) stimulated prolactin release in the primary culture of rat anterior pituitary cells.
Annexin 5, a novel calcium-phospholipid binding protein, is thought to be involved in hormone secretion by the anterior pituitary gland. Gonadotropin releasing hormone stimulates annexin 5 synthesis, which, in turn, enhances gonadotoropin secretion. On the other hand, annexin 5 was shown to inhibit prolactin release in vitro. To understand the nature of the opposing effects of annexin 5 on these two major pituitary hormones, the present study examines the inhibitory effect of annexin 5 on prolactin release in relation to thyrotropin stimulating hormone (TRH) using primary cultures of anterior pituitary cells of adult female rats. While recombinant rat annexin 5 was found to have little effect on basal prolactin release, it significantly inhibited TRH-stimulated prolactin release. Addition of specific anti-annexin 5 serum to the culture increased basal prolactin release in a concentration dependent manner, and no further increase in prolactin release was observed following application of TRH in the presence of anti-annexin 5. The enhanced basal prolactin release induced by anti-annexin 5 was reversed by the simultaneous administration of indomethacin, an inhibitor of cyclooxygenase. These results demonstrate that endogenous pituitary annexin 5 exerts an inhibitory effect on prolactin release and suggest that this is attained by suppression of eicosanoid synthesis in vitro.
Kawaminami
Mitsumori
M
Laboratory of Veterinary Physiology, School of Veterinary Medicine and Animal Sciences, Kitasato University, Towada, Aomori 034-8628, Japan.
Senda
Akio
A
Etoh
Seishi
S
Miyaoka
Hiroko
H
Kurusu
Shiro
S
Hashimoto
Inoru
I
D000818:Animals; D017304:Annexin A5 / Q000276:immunology / Q000494:pharmacology / Q000502:physiology*; D002478:Cells, Cultured; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D005260:Female; D007106:Immune Sera / Q000494:pharmacology; D007213:Indomethacin / Q000494:pharmacology; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D011994:Recombinant Proteins / Q000494:pharmacology; D013973:Thyrotropin-Releasing Hormone / Q000037:antagonists & inhibitors* / Q000494:pharmacology*
D017304:Annexin A5; D016861:Cyclooxygenase Inhibitors; D007106:Immune Sera; D011994:Recombinant Proteins; D013973:Thyrotropin-Releasing Hormone; D011388:Prolactin; D007213:Indomethacin