Chromogranin A, chromogranin B and secretogranin II mRNAs in the pituitary and adrenal glands of various mammals. Regulation of chromogranin A, chromogranin B and secretogranin II mRNA levels by estrogen.

BACKGROUND

The chromogranin/secretogranin (Cg/Sg) acidic proteins are widely distributed in vertebrate species. They are thought to play a role in hormone packaging within secretory granules, in hormone secretion, and serve as prohormones for various proteolytic cleavage products. The genes for most members of the Cg/Sg family have been cloned, so hybridization analysis can be used to analyze the distribution and regulation of Cg/Sg mRNAs in various vertebrate species.

EXPERIMENTAL DESIGN

The method of in situ hybridization was used to localize chromogranin A, chromogranin B, and secretogranin II in adrenal and pituitary tissues from laboratory animals and from humans in order to analyze the distribution of various Cg/Sg mRNAs in these tissues. To gain some insight into the regulation and possible functions of specific Cg/Sg members, female rats were ovariectomized for different periods with and without estrogen replacement and the pituitaries were subsequently analyzed by in situ hybridization and Northern hybridization analyses. Combined ISH and immunohistochemistry were used to localize the specific cell types in normal rat pituitary that expressed the mRNA for chromogranin A, chromogranin B, and secretogranin II.

RESULTS

All three Cg/Sg mRNAs were detected in pituitary and adrenal tissues of rats, mice, dogs, monkeys, and humans. Combined in situ hybridization and immunohistochemistry using rat pituitary revealed that the glycoprotein hormone-secreting cells expressed all three Cg/Sg mRNAs in approximately equal amounts. Ovariectomy followed by estrogen replacement resulted in decreased levels of CgA and SgII mRNAs. In contrast, the level of CgB mRNA, that was not changed by ovariectomy, was increased after estrogen treatment, probably secondary to prolactin cell hyperplasia.

CONCLUSIONS

The three principal Cg/Sg mRNAs are present in the adrenal and pituitary of various vertebrates. Estrogen plays a significant role in regulating the mRNA levels of different Cgs/Sgs suggesting functional and regulatory differences in Cg/Sg proteins.