Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:4.6.1.1 (adenylate cyclase)
 19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The radioreceptor assay system for TSH is considered to be useful in quantitating the hormone and analyzing the mechanism of its action. The assay was established, and the interaction of abnormal thyroid stimulators in Graves' patients was evaluated in this assay system. A 10,000xg fraction of human thyroid homogenates was used as the receptor. Human TSH supplied from NIH was iodinated by using lactoperoxidase. The binding of 125I-TSH to the receptor was small, and 125I-TSH was further purified by the receptor binding. The receptor (25mg equivalent), purified 125I-TSH, and standard TSH or a sample were incubated at 37 degrees C for 60 min in a final volume of 300 microliters. The binding of 125I-TSH to the receptor was time- and temperature-dependent with optimal binding under the conditions described above. The binding was completely inhibited by the addition of human, bovine and ovine TSH and partially inhibited by high concentrations of HCG, FSH-LH. However, there was no cross reactivity with insulin, prostaglandin E1, E2, T3, T4 and Nal. The assay was sensitive enough to detect 5 to 50 microU of TSH. The amount of TSH bound to the receptor was almost parallel to the TSH concentration which is necessary to stimulate human thyroid adenylate cyclase activity. Studies of dissociation kinetics and Scatchard plot indicated that there were two classes of TSH receptors in the human thyroid. A higher association constant was calculated as 1.5 x 10(8)M-1. LATS-IgG from a patient with Graves' disease completely inhibited the binding of 125I-TSH to the receptor, and studies of Lineweaver-Burk, plot suggested that TSH and LATS-IgG shared common binding sites. The radioreceptor assay of TSH appears to be useful in evaluating the abnormal thyroid stimulators present in Graves' disease.
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PMID:[Studies on the radioreceptor assay of TSH: the binding of 125I-TSH to the human thyroid receptor and the interaction of LATS-IgG (author's transl)]. 22 97

TSH-binding inhibitor immunoglobulins (TBII) have been detected not only in patients with Graves' disease but also in those with Hashimoto's thyroiditis by using the radioreceptor assay of TSH. In the present study, the properties of TBII in patients with Hashimoto's thyroiditis are discussed. Two (7%) of 29 patients with Hashimoto's thyroiditis had detectable levels of TBII in their gamma-globulin fractions. Both patients were untreated and clinically hypothyroid. One of them had no goiter, and her thyroidal 99mTc uptake was 0% (normal range: 0.4 approximately 3.0%). Despite having potent TSH-binding inhibitor activity in the TSH radioreceptor assay, her serum or its IgG fraction (H-IgG) did not contain any significant anti-TSH antibody, LATS, LATS-protector or human thyroid adenylate cyclase (AC) stimulating activity. This H-IgG inhibited both human thyroid AC stimulation and c-AMP increase in mice thyroid glands induced by TSH or LATS. Furthermore, her serum caused significant inhibition of 131I-release by LATS in a McKenzie mouse bioassay. The present study demonstrates that the serum of one patient with Hashimoto's thyroiditis contained antibodies which 1) blocked the binding of lablled TSH to the receptor, 2) had no thyroid-stimulating activity by themselves, and 3) inhibited AC stimulation by TSH. Such antibodies may cause unresponsiveness to TSH stimulation, hypothyroidism, and, if this state persists for a long time, eventually may result in atrophy of the thyroid tissue. Further, these data indicate that TBII detected by the TSH radioreceptor assay did not always show thyroid stimulating activities.
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PMID:[Studies on the radioreceptor assay of TSH: the properties of TSH-binding inhibitor immunoglobulins (TBII) in patients with Hashimoto's thyroiditis (author's transl)]. 22 99

To obtain an in vitro method of LATS assay which is equally sensitive to a McKenzie bioassay, we compared the quality of cAMP generation-stimulation, thyroidal adenyl cyclase stimulation, and the stimulation of T3-release from mouse thyroid slices. Among those indicators of thyroid stimulation, stimulation by IgG of the release of T3 from incubated thyroid slices is the most sensitive, reproducible and reliable indicator, reflecting faithfully the results of a McKenzie bioassay. Stimulation of cAMP generation in slice manifested less sensitivity, but reasonable reproducibility. However, adenyl cyclase stimulation by IgG of patients with Graves' disease was erratic in two successive experiments, probably due to a non-specific effect of IgG. When adenyl cyclase stimulation was adopted as a sole indicator of thyroid stimulation, the results must be interpreted cautiously.
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PMID:[A comparison of various indicators of murine thyroid stimulation by LATS (author's transl)]. 22

To characterize further the nature and site of the receptor for the IgG stimulator in Graves' disease, we have developed a preparative scheme to provide a bovine thyroid subfraction rich in plasma membranes. Pellets (800 X g) obtained from bovine thyroid homogenates were layered on a 30-64% continuous sucrose gradient (SG). The centrifuged gradient was divided into four portions (SG1, 2, 3, and 4); and these along with the 800 X g pellet were characterized in terms of their capacity to neutralize (bind) the biological activity of LATS, their specific binding of [125I]TSH, and their subcellular marker content. Subfraction SG1 contained the highest adenyl cyclase specific activity, the highest [125I]TSH binding specific activity, and vied with the 800 X g pellet and SG3 for the highest specific activity of LATS neutralization. Electron microscopy of SG1 showed a predominance of plasma membrane structures contaminated with a modest amount of cellular debris. Adenyl cyclase activity in SG1 was enhanced by TSH, LATS, and sodium fluoride. Although a dose-response curve could be established for TSH, a similar relationship could not be established for LATS. We conclude that activation of plasma membrane-bound adenyl cyclase is associated with neutralization of the biological activity of LATS. Further, the difference between [125I]TSH binding and LATS neutralization activity observed in the various thyroid membrane subfractions suggests that either LATS and TSH interact at different sites or have different mechanisms of binding at a common site.
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PMID:The subcellular localization of the long-acting thyroid stimulator inhibitor in bovine thyroid gland. 74 82

Forskolin, from the roots of the Indian medicinal plant Coleus forskohlii, has recently been shown to be a potent stimulator of adenylate cyclase in many systems, including endocrine tissues such as the thyroid gland. We describe forskolin activation of beta-naphthylamidase activity in guinea pig thyroid tissue using the cytochemical bioassay (CBA) for thyroid stimulators. This CBA is the most sensitive bioassay for TSH and LATS-B currently available, being able to detect stimulation by doses as low as 10(-5) mU TSH/l and 10(-9) mU LATS-B/l. The dose-response curve to forskolin was bell-shaped (as is seen with TSH and LATS-B) with the ascending limb of the curve produced by 10(-13) M to 10(-12) M forskolin after a 3 min exposure time. Maximal stimulation was observed with 10(-12) M forskolin. However, the dose-response curve to forskolin was not parallel to that given by TSH, the slope of the ascending limb being much greater. It has been suggested that stimulation of beta-naphthylamidase activity in the CBA is via cAMP. We report that dibutyryl cAMP at doses from 10(-16) M to 10(-11) M produces a bell-shaped dose-response curve with a very broad peak response, again not parallel to that produced by TSH. Forskolin activation of beta-naphthylamidase in the CBA is unaffected by a 1:10(6) dilution of 11E8, a monoclonal antibody raised against solubilised TSH receptors, which binds to the TSH receptor and inhibits TSH stimulation. Although the precise location of forskolin action is not known, this is further evidence that forskolin acts at a post-surface receptor site.
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PMID:Forskolin stimulation of naphthylamidase in guinea pig thyroid sections detected with a cytochemical bioassay. 298 70

Freeze-dried extracts (FDE) of the plants Lycopus virginicus, Lycopus europaeus, Melissa officinalis, and Lithospermum officinale, as well as products of the oxidation of certain of their constituents, have been shown to exert antithyrotropic activity by virtue of their ability to form adducts with TSH that bind weakly, if at all, to the TSH receptor. The thyroid-stimulating immunoglobulin G (IgG) found in the blood of patients with Graves' disease (Graves'-IgG) resemble TSH in their ability to bind to the thyroid plasma membrane, probably at the TSH receptor, and to activate the gland. In view of this similarity, and since some of the aforementioned FDE have been used in the treatment of hyperthyroidism in Graves' disease, we undertook studies of the effect of these FDE and their constituents on the binding and biological action of Graves'-IgG. In all samples of Graves'-IgG tested, incubation with antithyrotropic FDE or their antithyrotropic auto-oxidized constituents decreased their TSH-binding inhibitory activity in a dose-dependent manner. FDE from L. officinale also inhibited in a dose-dependent manner the direct binding to human thyroid membranes of a 125I-labeled preparation of receptor-purified Graves'-IgG. As judged from both stimulation of adenylate cyclase activity in vitro (thyroid-stimulating Ig activity) and enhancement of thyroid iodine release in the McKenzie assay system (LATS activity), antithyrotropic FDE and their auto-oxidized constituents also inhibited the biological responses to Graves'-IgG. FDE and constituents lacking antithyrotropic activity had little or no effect on the TSH-binding inhibitory activity, thyroid-stimulating Ig activity, or LATS activities of Graves'-IgG. Evidence of some degree of specificity of the inhibitory effects of the active compounds on Graves'-IgG was obtained in the demonstration that they failed to inhibit both the direct binding of [125I]insulin to its receptors in human lymphoblastoid IM-9 cells and the ability of IgG preparations containing antiinsulin receptor antibodies to inhibit the binding of labeled insulin. These observations suggest that the active principles in those FDE and their oxidized constituents with antithyrotropic activity may interact with the pathogenically important components of Graves'-IgG to inhibit their ability to bind to the TSH receptor and activate the thyroid, as they do with TSH. Our findings provide a possible rationale for the empirical, though poorly documented, use of FDE in the treatment of Graves' disease and some support for the suggestion that Graves'-specific IgG may have structural similarities to TSH itself.
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PMID:Extracts and auto-oxidized constituents of certain plants inhibit the receptor-binding and the biological activity of Graves' immunoglobulins. 298 57

In the sera of patients with Graves' disease abnormal thyroid 'stimulating' immunoglobulins have been demonstrated by in vivo and in vitro assay systems. Conflicting results have been reported when thyroid stimulating and thyrotrophin (TSH)-binding inhibiting activities have been compared. The present study was performed in forty-nine hyperthyroid Graves' patients to ascertain the relationships among TsH-binding inhibiting immunoglobulins (TBII), measured by a radio-receptor assay, thyroid stimulating antibody(TSAb), assayed by stimulation of adenylate cyclase-cAMP system in human thyroid plasma membranes, and LATS, measured by McKenzie's mouse bioassay.TBII was detected in twenty-one of forty-nine (42.9%), TSAb in thirty-five of forty-nine (71.4%) and LATS in nineteen of forty-nine (38.8%).TBII was also present in four of sixteen (25%) patients with other thyroid autoimmune disorders. When the results obtained with the different techniques were compared, correlation was found between LATS response and TSAb activity ( =0.53, P less than 0.001), while there was no correlation between TSAb and TBII activities and between LATS response and TBII activity. These data conform that TSAb is specific and sensitive marker of Graves' disease and suggest that TBII activity is not necessarily synonymous with thyroid stimulation, and could reflect a different phenomenon concomitantly produced.
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PMID:Comparison between thyroid stimulating and tsh-binding inhibiting immunoglobulins of Graves' disease. 611 13