Waalkes M P, Rehm S, Perantoni A
Laboratory of Comparative Carcinogenesis, National Cancer Institute, Frederick Cancer Research Facility, Maryland 21701.
Biol Reprod. 1988 Nov;39(4):953-61. doi: 10.1095/biolreprod39.4.953.
A deficiency of metallothionein, a high-affinity metal-binding protein thought to detoxify cadmium, has been observed in rat and mouse testes, tissues that are highly susceptible to the necrotizing and carcinogenic effects of cadmium. Like the testes, the ovaries undergo a hemorrhagic necrosis when exposed to cadmium, and female Syrian hamsters have recently been shown to be highly susceptible to cadmium. However, the nature of cadmium-binding proteins in the ovary is unknown; thus, this study was undertaken to define the nature of any such proteins in the Syrian hamster ovary. A low molecular weight (Mr) zinc- and cadmium-binding protein was detected in cytosol derived from the ovaries after gel filtration that eluted with a relative elution volume similar to authentic metallothionein. This protein was extractable by heat-treatment and sequential acetone precipitation. When such extracts were further purified with a reverse phase high performance liquid chromatography (HPLC) technique developed for the isolation of metallothionein isoforms, two forms were separated. However, neither of these could be classified as metallothionein on the basis of amino acid composition, since both were particularly low in cysteine, a very common amino acid in metallothionein. The ovarian protein also contained significant amounts of aromatic amino acids, unlike metallothionein--which is devoid of aromatics, and contained much more glutamate than metallothionein. Hamsters were also made resistant to cadmium-induced ovarian necrosis by zinc treatment. Such zinc treatment, however, did not alter levels of this protein, yet caused a marked induction of hepatic metallothionein. Likewise, cadmium treatment did not increase the levels of the ovarian metal-binding protein yet markedly induced hepatic metallothionein.(ABSTRACT TRUNCATED AT 250 WORDS)
金属硫蛋白是一种高亲和力的金属结合蛋白，被认为具有镉解毒作用。在大鼠和小鼠睾丸中已观察到金属硫蛋白缺乏，而睾丸组织对镉的坏死和致癌作用高度敏感。与睾丸一样，卵巢在接触镉时会发生出血性坏死，最近已证明雌性叙利亚仓鼠对镉也高度敏感。然而，卵巢中镉结合蛋白的性质尚不清楚；因此，本研究旨在确定叙利亚仓鼠卵巢中此类蛋白的性质。经凝胶过滤后，在卵巢细胞质中检测到一种低分子量（Mr）的锌和镉结合蛋白，其洗脱相对体积与 authentic 金属硫蛋白相似。该蛋白可通过热处理和连续丙酮沉淀提取。当用为分离金属硫蛋白异构体而开发的反相高效液相色谱（HPLC）技术对这些提取物进一步纯化时，分离出了两种形式。然而，根据氨基酸组成，这两种形式都不能归类为金属硫蛋白，因为它们的半胱氨酸含量特别低，而半胱氨酸是金属硫蛋白中非常常见的氨基酸。卵巢蛋白还含有大量芳香族氨基酸，这与不含芳香族氨基酸的金属硫蛋白不同，且其谷氨酸含量比金属硫蛋白多得多。通过锌处理也可使仓鼠对镉诱导的卵巢坏死产生抗性。然而，这种锌处理并未改变该蛋白的水平，但却显著诱导了肝脏金属硫蛋白的产生。同样，镉处理也未增加卵巢金属结合蛋白的水平，但却显著诱导了肝脏金属硫蛋白的产生。（摘要截断于250字）
