Abstract. The distribution of a number of membrane proteins on plasmalemmal microdomains (microvilli, coated pits) and in endosomes and lysosomes of the proximal tubule epithelial cell was determined in normal rat kidneys by immunofluorescence and immunoelectron microscopy. Two major brush border proteins, 130 and 94 kD, and 3,-glutamyl transpeptidase were detected on the membranes of the microvilli but were not found on membranes of coated pits. Gp330, the Heymann nephritis antigen, and clathrin were localized in coated pits. The lysosomal membrane glycoprotein, lgpl20 (Lewis, V., S. A. Green, M. Marsh, P. Vihko, A. Helenius, and I. Mellman, 1985, J. Cell Biol., 100:1839-1847) was restricted to lysosomes where it co-localized with ~-glucuronidase. Endosomes, identified by preloading with HRP injected 5-15 min before rats were killed, did not contain detectable amounts of any antigen tested. The distribution of the same proteins was also determined in rats given sodium maleate, which is known to slow or reduce protein absorption by the proximal tubule and to cause vacuolation of the endocytic apparatus. After maleate treatment the distribution of microvillar and lysosomal markers was unchanged, but the coated pit markers were redistributed--gp330 was concentrated in newly formed apical vacuoles, and clathrin was diffusely distributed in the apical cytoplasm or on apical coated vesicles. These findings indicate that the membrane composition of microvilli, coated pits, endosomes, and lysosomes is distinctive in the proximal tubule cell; and that gp330, unlike other known coated pit membrane components, is not transferred to endosomes during endocytosis. After maleate treatment, the coated pits lose their clathrin coats, and the corresponding membrane is internalized.

Cytokines such as interleukin-1␤ (Il-1) are produced in the brain during development and during inflammatory processes that result from lesions or disease. One function of Il-1 in the brain appears to be the stimulation of astrocytes to proliferate and produce a variety of cytokines and trophic factors, including nerve growth factor. The mechanisms by which Il-1 exerts its actions on astrocytes remain poorly defined. We present evidence that this cytokine elicits activation of the NFB transcription factor and that this transcription factor mediates effects of Il-1 on nerve growth factor mRNA expression. Elucidation of the processes by which cytokines activate astrocytes and influence trophic factor expression may provide insight into mechanisms governing inflammatory processes within the central nervous system.

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The etiology of human breast cancer is currently undefined. However, it has been hypothesized that exposure to chemical carcinogens may be an important factor. Extrapolation from rodent models for chemically-induced mammary cancer suggests the possibility that human mammary epithelial cells in situ might contain DNA adducts due to exposure to environmental chemicals. We have therefore screened breast epithelial cells from 10 donors for the existence of DNA adducts using the 32P-postlabeling assay. In order to validate this analysis technique, we also examined the DNA adducts formed in human mammary cells exposed to benzo[a]pyrene (B[a]P) in vitro, and adducts formed in rat mammary epithelial cells exposed to B[a]P in vitro and in vivo. Confirming previous results using HPLC analysis of [3H]B[a]P-DNA adducts, the major B[a]P-DNA adduct formed by human mammary epithelial cells in vitro was (+)-anti-B[a]P-7,8-dihydrodiol-9,10-epoxide (BPDE):deoxyguanosine. This adduct did not appear to be formed by rat mammary cells exposed to B[a]P in vitro. However, 32P-postlabeling analysis of mammary epithelial cell DNA from rats exposed to B[a]P in vivo indicated that (+)-anti-BPDE-deoxyguanosine was a major B[a]P-DNA adduct under these exposure conditions. When the mammary epithelial cells from 10 human donors were screened for DNA adducts formed in situ, cells from three donors exhibited distinct adduct patterns. None of these adducts appeared to be (+)-anti-BPDE-deoxyguanosine. The existence of DNA adducts in human mammary epithelial cells in situ, coupled with the data indicating that rat mammary cells form different B[a]P adducts in vitro and in situ, suggests the need for further study of human breast cell adducts.

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