Role of basic fibroblast growth factor in the pathogenesis of nodular goiter

Thyroid epithelial cells are known to produce several growth factors and cytokines which influence thyroid cell growth and function in an autocrine and/or paracrine manner. It is already known that insulin-like growth factor I (IGF I) is overexpressed in toxic adenomas whereas epidermal growth factor (EGF) is found predominantly in thyroid neoplasia. We now investigated the expression of bFGF by immunohistochemistry in thyroid tissue of patients with toxic adenoma (n = 27), cold nodules (n = 27) and for comparison in Graves' disease (n = 5). In addition bcl-2-oncoprotein expression in these tissues were also detected by immunohistochemistry. Most of bFGF immunostaining was found in the connective tissue of all thyroid tissues with a predominance in adenomas and in Graves' diseases. The collagen surrounding the thyroid follicles close to their basal membrane were homogeneously and intensively stained. All the cytoplasm of fibroblast in the connective tissue were strongly positive. Within the cytoplasm of only 2-10% thyroid epithelial cells bFGF immunostaining was found without any difference between toxic adenomas or cold nodules. In the tissue of patients with Graves' disease, less than 2% of thyrocytes were stained. All thyroid epithelial cell showed clearly an immunostaining for bcl-2-oncoprotein in nodular goiter as well as Graves' disease.

The inositol-1,4,5-trisphosphate system is involved in rapid effects of aldosterone in human mononuclear leukocytes

There is increasing evidence for rapid steroid action on electrolyte transport in human mononuclear leukocytes (HML). In HML, aldosterone stimulates the Na+/H+ antiporter within a few minutes. Because a variety of hormones and growth factors activate the Na+/H+ antiporter via protein kinase C and inositol phospholipids, a possible involvement of inositol-1,4,5-trisphosphate (IP3) in the rapid effects of aldosterone in HML was investigated. The stimulation of IP3 generation was started by the addition of aldosterone, concanavalin A, or other steroids. A significant increase in IP3 levels by aldosterone (1 nmol/L, P < 0.05) was found after 1 min, similar to that found after concanavalin A (25 micrograms/mL). Aldosterone caused a concentration-dependent elevation of IP3 levels, with an apparent EC50 of approximately 0.1 nmol/L. Fludrocortisone stimulated IP3 generation at similar concentrations, whereas a weaker IP3 stimulation by glucocorticoids (hydrocortisone, dexamethasone) occurred at micromolar concentrations only. Canrenone, a potent inhibitor of classical aldosterone action, was not effective up to a concentration of 100 nmol/L. These findings show kinetic and pharmacological similarities with both the functional data on Na+/H+ antiport stimulation by aldosterone and the studies of 125I-aldosterone binding to plasma membranes of HML. Thus, these data are the first to indicate an involvement of the phosphoinositide pathway in the rapid membrane effects of aldosterone.

Photoaffinity labeling of plasma membrane receptors for aldosterone from human mononuclear leukocytes

Non-genomic effects of aldosterone on the sodium-proton-antiport have been shown in human mononuclear leukocytes which could be related to a new aldosterone membrane receptor. In the present paper plasma membranes from human mononuclear leukocytes were covalently photolabeled with a [125I]-aldosterone derivative. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed significant aldosterone binding at a molecular weight of approximately 50000 Dalton which was absent with 1 microM cold aldosterone, but not cortisol in the binding media. The presence of the sulfhydryl agent dithiothreitol did not affect results suggesting the absence of disulfide bridges in the steroid binding domain of the receptor. These data are the first to define the molecular weight of the membrane receptor for aldosterone.