Characterization of big stanniocalcin variants in mammalian adipocytes and adrenocortical cells

The hormone stanniocalcin (STC) is widely distributed, and in rodents the highest levels of expression are in the ovaries. In both cows and rodents, ovarian STC consists of three high-molecular-weight variants collectively known as big STC. In the ovary, big STC is made by theca cells and interstiti...

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Published inAmerican journal of physiology: endocrinology and metabolism Vol. 52; no. 2; pp. 197 - 205
Main Authors PACIGA, Mark, HIRVI, Edward R, JAMES, Kathi, WAGNER, Graham F
Format Journal Article
LanguageEnglish
Published Bethesda, MD American Physiological Society 01.08.2005
Subjects
Adrenal glands
Biological and medical sciences
Body fat
Cattle
Cells
Endocrine system
Fundamental and applied biological sciences. Psychology
Hormones
Lipids
Mammals
Reproductive system
Rodents
Vertebrates: endocrinology
Characterization
Variant
Adipocyte
Vertebrata
Mammalia
Storage
stanniocalcin receptor
Adrenal cortex
adipose cells
Lipids
lipid storage droplets
Biological receptor
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Summary:The hormone stanniocalcin (STC) is widely distributed, and in rodents the highest levels of expression are in the ovaries. In both cows and rodents, ovarian STC consists of three high-molecular-weight variants collectively known as big STC. In the ovary, big STC is made by theca cells and interstitial cells and is targeted to lipid storage droplets of nearby luteal cells to inhibit progesterone release. An endocrine pathway is operative during pregnancy and lactation. Whether or not big STC is made by tissues other than ovary has never been addressed. Therefore, the purpose of this study was to determine via a detailed characterization of adrenal glands and adipocytes whether big STC is present in other cells that store and release lipids. The results showed that STC was made in bovine and mouse adrenals, mainly in steroidogenic, adrenocortical cells. The majority of ligand and receptor were likewise confined to cortical zone cells. As in luteal cells, high levels of ligand and receptor were found in the adrenocortical cell lipid droplet fraction. However, adrenals made only the largest (135 kDa) of the three big STC variants. Nonetheless, adrenal STC had much greater receptor affinity than a mixture of the three big STC variants. Adipocytes contained all three big STC variants, and both ligand and receptor were heavily concentrated on the lipid droplets. Moreover, adipocyte lipid storage droplets had 50-fold more receptors than those in steroidogenic cells, indicating that big STC is heavily targeted to adipose cells. The findings collectively support the hypothesis that big STC is not unique to ovarian steroidogenic cells but is in fact common to cells with a role in lipid storage and release. [PUBLICATION ABSTRACT]
ISSN:0193-1849
1522-1555