Estradiol Negatively Regulates Secretogranin II and Chromogranin A Messenger Ribonucleic Acid Levels in the Female Rat Pituitary but Not in the Adrenal

Abstract

Estradiol (E2) effects on the pituitary and adrenal secretogranin II (SgII) and chromogranin A (CgA) proteins and mRNA levels were analyzed in the adult female rat. Animals were ovariectomized or sham-operated for 2 weeks and then daily injected with various doses of 17 beta-E2 (from 5-100 micrograms) for the following week. SgII and CgA levels were determined by Western blot analysis using two specific antisera. Messenger RNA (mRNA) levels were measured by RNA slot blot analysis using specific cDNA probes. Simultaneously, pituitary LH content and gonadotropin subunit (LH beta, FSH beta, alpha) mRNAs were quantified. Ovariectomy promoted a significant increase in pituitary SgII and CgA proteins (2-fold vs. sham-operated animals, P less than 0.01) and a concomitant rise in their mRNA levels (2.5-fold and 4.5-fold for SgII mRNA and CgA mRNA, respectively, P less than 0.01). In the same animals LH beta, FSH beta, and alpha-subunit mRNA levels increased by 20-, 12-, and 6-fold, respectively. Estrogen replacement resulted in a parallel decrease of CgA and LH beta mRNA to the control values, starting from the lowest steroid dose (5 micrograms). The SgII mRNA decrease was initiated only with a higher concentration of E2 (10 micrograms), as was that of alpha-subunit mRNA; yet, the SgII mRNA level remained significantly higher than in the control pituitary, even with the highest steroid dose (P less than 0.05) at variance with the alpha-mRNA level. Concerning protein concentration, the postcastration increase in CgA was fully reverted with 10 micrograms E2 while that of SgII remained unaffected, as was the pituitary LH content. In the adrenal gland, neither the ovariectomy nor the E2 therapy altered significantly the SgII or CgA protein and mRNA concentrations. We conclude that, in rats, 1) ovarian factors regulate the pituitary SgII and CgA protein and mRNA steady-state levels while such factors are inefficient in the adrenal gland, 2) CgA and LH beta mRNAs exhibit the same sensitivity to E2 while SgII and alpha-subunit mRNAs appear less sensitive, and 3) SgII and LH pituitary contents present a similar pattern of variations when the estrogenic status of the animal is modified.

Regulation of Expression of Secretogranin II mRNA in Female Rat Pituitary and Hypothalamus

“…Since these results [36] were published after our studies of the estrous cycle had been completed, we repeated our studies taking particu lar care in determining the stage of the estrous cycle; again, we found the results shown in figures 3 and 4 that LH|I mRNA levels in the anterior pituitary gland in creased as the estrous cycle progressed from estrus through proestrus and that Sgll mRNA levels decreased as the cycle progressed (data not shown). This disagree ment is peculiar since we observed inhibition of Sgll and LH() mRNA levels by estrogen just as Anouar et al [37] previously reported. Thus, this seeming discrepancy in the pattern of Sgll mRNA levels during the estrous cycle will require further study for clarification.…”

Chromogranin A: current status as a precursor for bioactive peptides and a granulogenic/sorting factor in the regulated secretory pathway

“…The very high expression of CGA in pituitary, adrenal medulla, and parathyroid for example have prompted the study of the regulation of CGA biosynthesis by estrogen, glucocorticoids, vitamin D and calcium. CGA mRNA and protein abundance is suppressed by estrogen in the pituitary [33][34][35], and up-regulated by glucocorticoids in the pituitary and adrenal [25,[36][37][38]. CGA biosynthesis is enhanced by 1,25-dihydroxyvitamin D-3 in the parathyroid gland [39,40], although parathyroid hormone biosynthesis is inhibited by di-hydroxyvitamin D-3 [39].…”

“…a Rat adrenal medulla, [37]; b rat anterior pituitary, [38,154] c rat adrenal medulla, [50]; a AtT20, [45]; e bovine chromaffin cells [25]; f PC12 cells, [155]; g parathyroid cells [47]; h rat pituitary and pituitary cells in culture (decrease in CGA and SglI mRNA), [33,34]; i rat pituitary (decrease in CGA, slight increase in CGB and SglI mRNA), [35]; J rat pituitary, increases with estrogen, decrease with dexamethasone in CGB mRNA, [156]; k parathyroid [40]; i rat adrenal, [37]; m rat adrenal, [50]; n bovine chromaffin cells (slight increase in CGA mRNA with forskolin treatment after 48 h, decrease with PMA alone and block of dexamethasone increase by PMA), [25]; o bovine chromaffin cells (no change in CGA mRNA after potassium or nicotine depolarizationi slight but not significant increase in CGA mRNA after 24 h with forskolin; increased SglI mRNA after 24 h with forskolin and potassium) [50]; p PC12 cells, no change in CGA or SglI mRNA with forskolin or PMA and increased CGB mRNA after both forskolin and PMA, [55]; q bovine chromaffin cells, CGB mRNA: occasional slight increase with K ÷, slight increase forskolin, no change after PMA treatment, C.-M. Hsu, L. Eiden, unpublished observations; r PC12 cells, increase in CGB mRNA and decrease in SglI mRNA after treatment with forskolin or 8-Br-cAMP, [157,158]; s rat insulinoma (RIN cells), CGA mRNA: no change after forskolin, blockade of dexamethasone induction with PMA but no effect of PMA alone, [25]; t SK-N-SH human neuroblastoma cells, decreased CGA mRNA after PMA, S.-H. Hahm, L. Eiden and A. lacangelo, unpublished observations; u SY-5Y human neuroblastoma cells, decreased CGA mRNA and increased SgII mRNA after PMA, [52]; v bovine chromaffin cells, no significant change in CGB or CGA mRNA after K ÷, [41].…”

Identification of a Novel Secretogranin II-Derived Peptide (SgII187–252) in Adult and Fetal Human Adrenal Glands Using Antibodies Raised against the Human Recombinant Peptide1

“…First, SgII is exclusively expressed in endocrine and neuronal cells and is stored in secretory vesicles from which it is released upon stimulation (1-3). Second, the synthesis of SgII is finely regulated by mechanisms generally operating on other hormones and neuropeptides (7,11,33,34). Third, like neuropeptide precursors, SgII contains several pairs of basic residues that represent potential cleavage sites by the subtilisin/kexin-like PCs (35,36).…”