Purification and characterization of creatine kinase, an estrogen-induced uterine protein (IP) from immature rats

Characterization of a uterine luminal fluid protein ULF-250 using N-terminal microsequencing and RT-PCR identifies a novel estrogen-regulated gene in the rat uterus

We had previously identified an estrogen responsive protein ULF-250, synthesized and secreted by the estrous rat uterus, which is immunologically distinct from complement C3 and alpha2-macroglobulin. The N-terminal microsequencing of ULF-250 followed by sequence homology analysis showed that this protein is a new member of a class of estrogen responsive proteins in the uterus. Polymerase chain reaction with a ULF-250 specific primer yielded partial sequence information of its message. The observed pattern of ULF-250 message in the uterus during the various stages of the reproductive cycle in the rat suggested a possible regulation of ULF-250 message by 17beta-estradiol. Upstream sequencing of ULF-250 message and its promoter domains would provide insight into the mechanism of its regulation by estradiol.

In situ hybridization for creatine kinase-B messenger RNA in rat uterus and brain

Creatine kinase-B (CKB) is present in both uterus and brain, and in uterus its synthesis (protein and mRNA) is regulated by estrogen. In the present study we have used in situ hybridization to detect CKB mRNA in uterus and brain, and to determine whether there is cell type specific induction of CKB by estrogen in these tissues. Tissue was taken from ovariectomized (ovx) rats that had been injected with either estrogen (17 beta-estradiol-3-benzoate and/or 17 beta-estradiol) or vehicle alone, 2, 8, 24 and 72 h previously. The brains and uteri were removed, frozen, cryostat-sectioned, and processed for in situ hybridization histochemistry. The uterine and brain sections were incubated with a tritiated DNA probe complementary to a 3' fragment of CKB mRNA, or a control sense probe to the same 3' fragment. In uterine smooth muscle cells, a 2.5- and 3.5-fold induction of CKB mRNA was observed 2 and 24 h after estrogen administration, respectively, and levels approached ovx controls at 72 h. A smaller induction (1.9-fold, 2 h) was observed in uterine epithelium, with little induction of CKB mRNA in stroma. In the brain CKB mRNA was detected in neurons, but not in clearly identified glia, and only occasionally in ependymal cells. In brain regions containing estrogen receptors there was no evidence of a significant estrogen effect on CKB mRNA levels. Some brain regions had higher neuronal expression than others (e.g. medial septum vs. preoptic area), but expression was widespread and not limited to neuroendocrine sites.

Risk assessment of the mycotoxin zearalenone

Trans-zearalenone, a resorcylic acid lactone, also known as F-2 toxin, is a nonsteroidal estrogenic mycotoxin produced by numerous species of Fusarium. As a result zearalenone is found in a number of cereal crops and their derived food products. A closely related substance "zeranol" (zearalanol) is at present being used in the United States and Canada as an anabolic agent in beef cattle. Zearalenone has been implicated in numerous incidences of mycotoxicosis in farm animals, especially pigs. In this report the health risks to Canadians due to the presence of zearalenone in food products have been evaluated. The first part of the report deals with the physicochemical aspects, mycology, laboratory production, and natural occurrence in plant products and animal products of zearalenone. The stability of zearalenone in foods and feeds, the effects of food processing, and the removal from foods and feeds by physicochemical means are also discussed. From these data the daily exposure of Canadians to zearalenone from food consumption has been estimated to be in the range of 0.05-0.10 microgram/kg b.w./day (mean and 90th percentile of eaters, respectfully) for young children, the highest consumption group on a body weight basis. The second part of the report deals with the metabolic disposition of zearalenone as well as the available toxicity data base of zearalenone in laboratory animals, farm animals, and humans. Studies in various species (rodents, rabbits, pigs, monkeys) including man have shown that zearalenone has estrogenic and anabolic activity. Its major effects are on reproduction, including reproductive organs and their function, leading to hyperestrogenism. Zearalenone has been implicated in numerous incidences of hyperestrogenism in farm animals, especially pigs. For reproductive effects a no adverse effect level (NOAEL) of 0.06 mg/kg b.w./day was estimated for the pubertal pig, the most sensitive species tested. Important differences in the biotransformation of zearalenone were noted, with greater amounts of alpha-zearalenol, the more estrogenic metabolite, formed in man and the pig compared to rodents. In addition, the biological half-life of these substances was longer in man than in other species tested. The binding of zearalenone to estrogen receptors was approximately 20-fold lower than that seen with 17 beta-estradiol in several assays.(ABSTRACT TRUNCATED AT 400 WORDS)

Separation and identification of two components of an estrogen-responsive, calcium-dependent arginine esteropeptidase

Arginine esteropeptidase is an estrogen-responsive, calcium-dependent enzyme in rat uterine cytosol. It appears in increased amounts 3 h after administration of physiologic amounts of 17 beta-estradiol to an immature female rat. Its reaction was resolved into two parts: a calcium-dependent activation of the enzyme and a calcium-independent hydrolysis of the substrate. The esteropeptidase was separated by DEAE cellulose chromatography into two components. The properties of component A, the activator, are distinct from those of component B, the enzyme, which has the same response to inhibitors as serine proteinases. Both components are subject to estrogen control. Component A is present in significant amounts only after estrogen stimulation. Component B is increased 3-fold after estrogen stimulation. The responses of the two components to inhibitors, their different molecular weights and chromatographic behavior and the pH optima of their reactions distinguish them from each other and from other uterine proteinases previously described.

Comparative analysis of rat uterine estrogen-induced creatine kinase with monoclonal antibodies

Monoclonal antibodies were generated against rat uterine estrogen-induced protein--creatine kinase (CK-EIP)--and two (MAb-28 and MAb-78) were studied. These antibodies were IgM but differed in their complementary antigenic determinants both of which were detectable on denatured but not on native CK-EIP. MAb-28 reacted with other CK-BBs but not with CK-MMs whereas MAb-78 reacted with both types of CKs. A measurement of antigenicity with the monoclonal antibodies under calibrated conditions showed differences among the CKs, notably between CK-BB from rat brain and CK-EIP when both were probed with MAb-28. The antigenicity of CK-BB (rat brain) was significantly lower than that of CK-EIP, indicating that the former either expresses less copies of the determinant recognized by MAb-28 than CK-EIP does, or possesses a determinant which interacts with the antibody with lower affinity. The monoclonal antibodies should help elucidate structure-function relationships in CK-BB and CK-EIP molecules, their anatomic distribution and their physiologic, pathologic and experimental variations in relation to gene expression induced by sex hormones.

Oestradiol-BSA conjugates for receptor histochemistry: problems of stability and interactions with cytosol

The validity of histochemical methods for the localization of hormone receptors based on the binding of fluorescent bovine serum albumin conjugates of oestradiol was examined with respect to their stability and their interactions with the oestrogen receptor type I. Stability was assessed by measuring free oestrogen in conjugates by radioimmunoassay and/or receptor protein binding assay. Sufficient free oestrogen--in order to saturate type I and type II binding sites (ER I, ER II)--was detected in freshly prepared conjugates. This free oestrogen originates in inadequate removal of adsorptively bound original ligand after synthesis. Apart from this fact, conjugates appeared to be unstable in aqueous solutions, especially under the conditions used for for histochemical methods. Free oestrogen extracted from the conjugates was subjected to high performance liquid chromatography. Amongst the eluted peaks, oestradiol and/or the original ligand used for synthesis were identified. The in vitro interaction of conjugates with oestrogen receptors was studied by competitive binding analysis and by incubation of cytosol with a Sepharose-bound conjugate. The results, especially those concerning the amount of free oestrogen, suggest that neither ER I nor ER II is involved in the staining mechanism of conjugates.