Biomedical subjects
Publications and source records attributed to M Bortolussi.
The tubular localization of binding sites for 125I-FSH is demonstrated in vitro by the autoradiography on frozen sections of boar-testis. The uniform distribution of silver grains throughout the seminiferous epithelium suggests the presence of receptors for FSH also in the adluminal compartment. Similar results have been obtained using rat testis.
The binding of 125I-labelled rat FSH to homogenates and frozen sections of mallard duck testis was investigated. The equilibrium association constant (Ka) in the homogenates (8.5 x 10(9) M-1) was similar to those reported in other avian and mammalian species. Autoradiography suggested that the binding sites for the labelled hormone were localized in the tubular compartment.
The LH(HCG) receptors in the ovaries of immature rats which were either untreated, or primed with PMSG and HCG, have been studied with a histochemical method which has proved to be as effective as when earlier used in the rat testis. This method, which consists of the topical application of 125I-HCG to picric acid-formaldehyde (PAF) fixed frozen sections followed by autoradiography, is also suitable for quantitative studies on the distribution of receptors. In the ovary of the immature 26 days old rat, the LH(HCG) receptors are localized exclusively in the interstitial and thecal tissues. After PMSG treatment many receptors appear in the granulosa of the large antral follicles. These receptors are most numerous in the outer layers of cells and least numerous in the inner. At the same time there are fewer receptors in the thecal and interstitial cells which have undergone the process of luteinization. After PMSG and HCG treatment the newly formed corpora lutea have few receptors, but these become progressively more numerous on subsequent days. It is suggested that, in the rat, the luteinization of the ovarian LH-target cells is associated with an initial decrease in the number of their LH(HCG) receptors.
PAF (picric acid-formaldehyde) fixation of rat testis for a short time at 0-4 degrees C was found to give satisfactory histological results and to preserve most of the specific binding activity of LH(HCG) receptors. Investigations of the characteristics of the hormone-receptor reaction after mild PAF fixation indicated that this reaction was not substantially affected in hormne receptor affinity and its own specificity; only the capacity of the receptors was lowered by about 20%. A histochemical model is presented whose main features are: fixation of testis tissue in PAF; freezing in liquid nitrogen and cutting in the cryostat; radiolabelled hormone-receptor binding reaction performed on the sections; autoradiography to reveal the binding reaction. The utility of the method for qualitative and quantitative receptor studies and its possible application to biopsy and surgical specimens, are discussed.
Standard suspensions of interstitial cells in PBS were exposed to the action of various fixatives, solvents (clearing agents), temperatures and U. V. light, in order to establish the effects of such chemical and physical agents on the HCG receptors. After exposure to the various agents, the interstitial cells were incubated with [125I]HCG for 2 h at 37 degrees C. To check the specificity of the reaction, competitive tests were performed with added excess non-iodinated HCG. Only formaldehyde fixation for short periods of time, preserved satisfactorily the specific binding activity of the receptors. A different degree of thermolability of the receptors was demonstrated, in relation to 37, 45, 54 and 60 degrees C, while freezing in liquid nitrogen had no effect on the receptors binding activity. After the binding reaction, solvents had a significant solubilizing effect on the HCG-receptor complexes. U. V. light had no significant damaging effect on the receptors. The application of the results for a histochemical approach to the study of the HCG receptors is discussed.
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