Immunocytochemical and autoradiographic demonstration of prolactin binding to human breast cancer cells in tissue culture

Identification of leptin receptors in lung and isolated fetal type II cells

Leptin is a cytokine involved in regulation of the satiety response. Receptors for this protein have been identified in brain as well as many other peripheral tissues. Some of the highest levels of receptor concentration occur in the lung. Considering the cellular diversity of lung, neither the localization nor the function of leptin in pulmonary tissues has been delineated. The purpose of the present study was to determine if fetal and adult rabbit lung displayed specific binding for leptin, to identify the binding sites, and to explore a potential functional role for leptin in lung surfactant production. Frozen sections of adult and fetal rabbit (24th gestational day) lung were prepared and incubated with increasing concentrations of [125I]leptin in the presence or absence of 1-microM-unlabeled leptin. Sections were removed and radioactivity measured. Concurrently, sections were coated with nuclear Trac emulsion and incubated in the dark at -30 degrees C. Lung showed specific binding for leptin. Microscopically, [125I]leptin was localized to acinar-lining epithelium of developing fetal lung. Larger cells within the epithelial layer appeared to bind leptin more avidly than adjacent cells. Antibodies to the leptin receptor were used to identify binding sites in adult lung and isolated fetal lung type II cells. In adult lung, both the K20 (against the extracellular amino-terminal) and the M18 antibody (against the intracellular carboxy-terminal) displayed several binding sites. In contrast, the isolated fetal type II cells showed only a single binding site for both antibodies. The apparent molecular mass of the receptor using the K20 antibody appeared to be approximately 125 kD. A protein of similar mass bound the M18 antibody suggesting that functional receptor is present in lung and expressed by fetal type II cells. Incubation of isolated fetal type II cells with leptin (0.01-10 microg/ml) stimulated [3H]choline incorporation in disaturated phosphatidylcholine. These results show that fetal and adult lung bind leptin specifically, and fetal type II cells in particular, may be responsive to leptin stimulation of phospholipid production. Leptin may therefore be important in regulating maturation of cells of the fetal lung.

An immunohistochemical study of the incidence and significance of human gonadotrophin and prolactin binding sites in normal and neoplastic human ovarian tissue

An immunoperoxidase technique has been utilised for the demonstration of follicle stimulating hormone (FSH), luteinising hormone (LH) and prolactin (PRL) binding sites in normal human ovaries and in a wide range of benign and malignant epithelial tumours of the ovary. The incidence of FSH, LH and PRL binding was, respectively, 32%, 41% and 39% in normal ovaries, 30%, 18.5% and 22.5% in benign epithelial tumours and 51%, 32% and 43% in malignant epithelial neoplasms. The incidence of FSH binding was significantly higher in malignant epithelial neoplasms than in either normal ovaries or benign epithelial tumours but otherwise no correlation was found between hormone binding capacity and the degree of malignancy of epithelial ovarian tumours, the histological type of the tumour, the degree of differentiation of the malignant epithelial tumours or the presence or absence of metastatic disease. Well differentiated malignant tumours did, however, tend to stain more strongly than did poorly differentiated neoplasms, thus suggesting that the number of binding sites per cell tends to decrease with decreasing degrees of differentiation.

Target cell prolactin, II

Is the entry hypothesis compatible with all the existing data about "the" second messenger for prolactin listed in Section II? All of these messengers, in some way either participate in, or modify, prolactin's actions or, in an end point-dependent manner, may actually mimic prolactin. There remains considerable uncertainty as to whether these findings reflect phenomena, some independent of and others quite dependent upon entry, on the one hand, or merely portions of a relatively large number of molecular cascades, some (but not necessarily all) begun initially at the plasmalemma and many (if not all) orchestrated toward completion by intracellular prolactin or agonist-receptor complex.

The localization of prolactin binding sites in human breast tissue

An immunohistochemical method involving the application of purified human prolactin and a specific antiserum to human prolactin, followed by the peroxidase-anti-peroxidase immunoperoxidase technique, has been used to detect prolactin binding in benign and malignant human breast tissue. The use of fresh, frozen material has been found to be essential. Prolactin binding has been shown to be a consistent feature of benign breast tissue but a variation within samples has been noted which is irrespective of hyperplastic changes. Fifty six percent of breast carcinomas gave a positive reaction but heterogeneity of binding has been shown to be a significant feature. A relationship between the presence and extent of prolactin binding and good histological differentiation of the tumours has been noted. It is concluded that immunohistochemistry is a suitable method for the demonstration of prolactin binding sites in human breast tissue and can provide useful information with regard to tumour heterogeneity.