Annexin 5 Inhibits Thyrotropin Releasing Hormone (TRH) Stimulated Prolactin Release in the Primary Culture of Rat Anterior Pituitary Cells

Abstract

Abstract. 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.

Proteome and radioimmunoassay analyses of pituitary hormones and proteins in response to feed restriction of dairy cows

“…As a further protein associated with the hormone secretion process 45 we found two spots for annexin A5 that were significantly higher expressed in the feed‐restricted group. An additional annexin A5 spot (spot 156, Supporting Information Table 1) was identified at the same MW as spot 6 and 7 indicating that annexin A5 occurs with different PTM.…”

“…An additional annexin A5 spot (spot 156, Supporting Information Table 1) was identified at the same MW as spot 6 and 7 indicating that annexin A5 occurs with different PTM. Although it is known that annexin A5 inhibits PRL release 45 and annexin A5 synthesis is enhanced in the presence of TH, gonadotropin releasing hormone, or after ovariectomy 46, a link directly referring to feed intake has not been reported so far. Also, secretogranin V (neuroendocrine polypeptide 7B2) is involved in the hormone secretion process.…”

The relevance of ANXA5 genetic variants on male fertility

“…Since 1992, Kawaminami and colleagues have studied the relationship between annexin A5 and prolactin in rats both in vivo and in vitro using rat pituitary primary cell cultures. However, their findings are inconsistent [22][23][24][25]. Nevertheless, annexin A5 generally decreases the secretion of prolactin in the studies mentioned above.…”

Expression and thyroid hormone regulation of annexins in the anterior pituitary

“…Scale bar, 500 mm. gonadotropes (Kawaminami et al 1998a(Kawaminami et al , 2004 and in vitro studies indicated that A5 not only enhances gonadotropin secretion following stimulation by gonadotrophin-releasing hormone (GnRH; Kawaminami et al 2002), but also stimulates basal PRL secretion while counteracting thyrotrophin-releasing hormone (TRH) induced PRL release albeit at exceedingly high concentrations (Kawaminami et al 2004). However, in vivo studies deciphering a biological function of A5 in the pituitary or other tissues are still missing and mice with a targeted disruption of the A5 gene have not revealed any obvious abnormalities (Brachvogel et al 2003), presumably due to the redundant function of other family members.…”