Changes in the expression of annexin A1 in the anterior pituitary gland after ovariectomy in rats

Abstract

The expression of annexin A1 (ANXA1) is augmented by gonadotrophin releasing hormone (GnRH) in LβT2 gonadotroph. We examined the distribution of ANXA1 in the pituitary tissues and the effect of ovariectomy. ANXA1 was mainly stained on folliculostellate cell-like irregular shaped cells with extended process of adult female rats. Large gonadotroph, so called castration cells, appeared two weeks after the ovariectomy. ANXA1 in castration cells exists around cells although another GnRH responsive annexin, ANXA5, was apparent also in the cytoplasm. The pituitary expression of ANXA1 after ovariectomy was significantly higher than intact rats. These difference in tissue distribution of two annexins suggest ANXA1 and ANXA5 bear different physiological function in the gonadotroph under GnRH regulation.

Keywords: annexin A1 (ANXA1); annexin A5 (ANXA5); gonadotroph; gonadotrophin releasing hormone (GnRH).

Fig. 1.

Changes in annexin A1 (ANXA1) in the pituitary tissues 2 weeks after ovariectomy in rats. (A), (B) Pituitary tissues of sham operated and ovariectomized rats 2 weeks before were subjected to immunohistochemistry for ANXA1 and ANXA5. Scale bar is 10 μm. Large castration cells (red arrows) appeared 2 weeks after ovariectomy. (C) Whole pituitary gland of sham operated or ovariectomized rats (OVX, n=4 respectively) were homogenized and sonicated in sample buffer. Protein sample was subjected to sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting. β-actin was utilized as internal control. The expression of ANXA1/β-actin was shown as mean ± SEM. *P<0.05.

Fig. 2.

Immunohistochemical analysis of ANXA1 in the pituitary tissues of 2 week after ovariectomy. Pituitary tissues of intact and ovariectomized (OVX, 2 weeks before) rats were subjected to immunohistochemistry for ANXA1 (A, B, C) and ANXA5 (D, E, F). Large castration cells (red arrows) are found in the pituitary of OVX rat. Green signal reveals ANXA1 and ANXA5. Blue in C and F is 4’,6-diamidino-2-phenylindol (DAPI). Cytoplasm of castration cell shows low immune-reaction of ANXA1, and extracellular space and other cells are more intensive. ANXA5 intensely distributes to cytoplasm. Intranuclear positive staining was seen. ANXA5 is green color and blue is DAPI.