Metallothioneins (MTs) as a family of low molecular weight, heavy metal-binding proteins characterized by a high cysteine content and lack of aromatic amino acids. MTs bind 7 to 12 heavy metal atoms per molecule of protein. They are ubiquitous in the animal and plant kingdoms and are found in prokaryotes. In mammals, the cysteine residues are absolutely conserved and serve to coordinate heavy metal atoms such as zinc, cadmium, and copper via mercaptide linkages.
General function
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Cellular localization
Cytoplasmic
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Ovarian function
Luteinization
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Expression regulated by
LH
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Ovarian localization
Theca, Luteal cells
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Espey LL, et al 2003 reported the Metallothionein-1 messenger RNA transcription in steroid-secreting cells of the rat ovary during the periovulatory period.
An increase in metallothionein 1 (MT-1) mRNA was detected in the ovaries of immature Wistar rats that were primed with s.c. injection of 10 IU eCG followed 48 h later by 10 IU hCG s.c. to initiate the ovulatory process. Ovarian RNA was extracted at 0, 2, 4, 8, 12, 24, 72, 144, and 288 h after the primed animals were injected with hCG. These extracts were used for reverse transcription polymerase chain reaction (RT-PCR) differential display and Northern analyses that yielded complementary gene fragments for MT-1. Expression of MT-1 mRNA increased significantly by 24 h after hCG treatment and reached a peak at 144 h after hCG. In contrast, a disintegrin and metalloproteinase with thrombospondin motifs and a tissue inhibitor of metalloproteinase 1, which were also detected by the RT-PCR differential display procedure, reached a peak at 12 h after hCG and returned to control levels in the ovaries by 72 h after hCG. In situ hybridization indicated that most of the MT-1 mRNA was expressed in the vicinity of the theca interna of preovulatory follicles and in the lutein granulosa of postovulatory follicles. Thus, MT-1 mRNA expression is primarily in the vicinity of steroid-secreting areas of the ovary. The substantial increase in MT-1 mRNA expression might be important in protecting the ovarian tissues from oxidative stress generated by ovarian inflammatory events during the ovulatory process and luteinization.