Identification of kallikrein in cultures of adult renal cells

A human skeletal muscle cell line obtained from an adult donor

A cell line (RCMH) in permanent culture was established from surgically removed adult normal human skeletal muscle by exposure to conditioned media obtained from thyroid cells. Cells proliferated indefinitely but displayed density inhibition of growth while maintaining some differentiated markers. Under certain incubation conditions, cells fused into myotube-like structures, with a concomitant increase in muscle specific proteins, such as human myoglobin, skeletal muscle myosin, desmin and dystrophin, as identified using immunocytochemical procedures. In addition, RCMH cells displayed high affinity receptors for alpha-bungarotoxin (Bmax = 0.7 pmol/mg protein, Kd = 1.5 nM) and dihydropyridines (Bmax = 0.3 pmol/mg protein, Kd = 0.5 nM for [3H]PN200-110); these values are comparable to those reported for muscle cells in primary culture. Patch-clamp studies showed the presence of 42 pS carbachol gated channels and of 5 pS calcium channels (current carried by barium); chloride and potassium channels were also seen. This new cell line appears to be a convenient model system to study skeletal muscle function.

Cellular and subcellular distribution of 2,4-dinitrophenyl groups in mouse epidermis and regional lymph nodes after epicutaneous application of 2,4-dinitrofluorobenzene

The cellular and subcellular distribution of 2,4-dinitrophenyl (DNP) groups in the epidermis and regional lymph nodes of the mouse was investigated after epicutaneous application of 2,4-dinitrofluorobenzene (DNFB) to sensitized and non-sensitized mice. The peroxidase-antiperoxidase method and the immunogold technique were used to visualize the DNP groups at both light and electron microscopic levels. The highest intensity of immunolabelling was found on tonofilaments of keratinocytes present in the upper layers of the epidermis. On the other hand, in vitro experiments showed that DNFB has the capacity to bind keratin which, together with immunocytochemistry, suggests that this molecule may be one of the skin protein carriers for DNFB. In addition, intense immunostaining for DNP was observed in the Golgi area of some epidermal Langerhans cells. Cells immunoreactive to DNP were also observed in the marginal sinus of cervical lymph nodes 6, 12 and 24 h after challenge. Immunoelectron microscopy revealed immunoreactive DNP groups in phagosomes of Langerhans cells at this site. The present findings support the hypothesis that the hapten DNFB penetrates passively into the cytoplasm of Langerhans cells, concentrates in the Golgi area and, during the migration of Langerhans cells to the lymph nodes, it is probably processed in the lysosomes before its presentation to T lymphocytes.

Vectorial secretion of a kallikrein-like enzyme by cultured renal cells. I. General properties

Urinary kallikreins are proteolytic enzymes known to be secreted by distal nephron tubules. In this study, we demonstrate (using the chromogenic tripeptide substrate S 2266) that the renal cell line A6 from Xenopus laevis secretes a kallikrein-like enzyme. Secretion is present only when the cells are grown on filters, and enzyme is secreted only into the apical membrane bathing solution. Enzyme secretion consists of two components, one soybean trypsin inhibitor (SBTI) sensitive (SSBTI) and the other insensitive to SBTI (ISBTI). Both enzymes were inhibited by aprotinin, a kallikrein-like enzyme inhibitor. Using a bioassay, only the ISBTI enzyme produced a hypotensive effect on blood pressure and is thus a kallikrein-like enzyme. The apical membrane of cells grown on filters contains both enzyme species, whereas the basolateral membrane contains only the ISBTI (kallikrein-like) enzyme. Both enzymes were present in the apical membrane of cells grown on plastic. Initiation of enzyme secretion occurred after the cells formed electrically tight monolayers and the increase in membrane activity always preceded enzyme secretion. Using an irreversible inhibitor of the apical membrane-bound enzymes, the turnover rate for the SSBTI and ISBTI enzymes (cells on filters) was 3 and 7 h, respectively. Because the recovery of enzyme secretion was proportional to the recovery of membrane-bound enzyme activities, this suggests that enzyme secretion is due to the release of membrane-bound enzyme.