Identification and characterization of leukotriene C4 and D4 receptors on a cultured smooth muscle cell line, BC3H-1

A sensitive rosetting assay for detection of acetylcholine receptor antibodies using BC3H-1 cells: positive results in 'antibody-negative' myasthenia gravis

Antibodies to acetylcholine receptor (AChR) were measured in a group of patients with myasthenia gravis (MG), some of whom had previously been classified as 'antibody negative' using the standard anti-AChR radioimmunoassay (RIA). AChR antibodies were measured using the rosetting assay, a new detection method which utilizes protein A-coated red blood cells and live BC3H-1 cells, a murine cell line which expresses muscle nicotinic AChR. The results of the rosetting assay were compared with those obtained in the anti-AChR RIA. 76% of all myasthenic sera tested showed rosetting at titers higher than any of the control sera (from patients with non-myasthenic neurologic disease and normal individuals). Of the myasthenic patients previously classified as 'antibody negative' in the RIA using human AChR, 71% demonstrated positive rosetting. There was no correlation between the anti-AChR antibody titer obtained in the rosetting assay and that obtained in the RIA using either human or denervated rat AChR. The results suggest that the rosetting assay may measure a subpopulation of antibodies that differs from those detected in the RIA.

Leukotriene-D4 induced cell shrinkage in Ehrlich ascites tumor cells

The nature of the leukotriene-D4 (LTD4) induced cell shrinkage in Ehrlich ascites tumor cells has been investigated. LTD4 treatment of Ehrlich cells induces net loss of cellular KCl and cell shrinkage independent of the initial cell volume. LTD4 also produces water loss and reduction in cell volume when all extracellular and all intracellular Cl has been replaced by NO3. On the other hand, LTD4 fails to produce any significant changes in cell volume in the presence of the K-channel blocker quinine, suggesting that LTD4 in Ehrlich cells induces Cl-independent K loss through the Ca2+-dependent K channels. However, the effect of physiological doses of LTD4 on cell volume seems not to be as potent in Cl-free, NO3 cells when compared to Cl-containing cells, indicating that LTD4 in Ehrlich cells also provokes Cl-dependent K loss. LTD4 seems not to produce K loss through an electroneutral K+/H+ exchange system. LTD4 still produces Cl-independent K loss and cell shrinkage in the presence of the anti-calmodulin drug pimozide but not in the presence of the LTD4 receptor antagonist L-649,923 or the 5-lipoxygenase inhibitor NDGA. Pretreatment of the cells with pertussis toxin, which inactivates inhibitory guanine nucleotide binding proteins (G-proteins), leads to partial inhibition of the LTD4-induced shrinkage. It is suggested that the LTD4-induced activation of K and Cl transporting systems in Ehrlich ascites tumor cells is mediated via a G-protein coupled receptor and that LTD4 might exert its effect through another lipoxygenase product. The Ca2+-calmodulin complex is not involved in the LTD4-induced activation of K and Cl transporting systems.

Leukotriene receptors

Leukotrienes are metabolites of arachidonic acid catalyzed by a novel lipoxygenase specific for the C-5 position. These fatty acids have many pharmacological properties including smooth muscle contractions and leukocytes activation, and are believed to play a key role in inflammatory and hypersensitivity reactions. Experimental evidence suggests that the action of leukotrienes is mediated by specific receptors. In this paper pharmacological and biochemical data in favor of the existence of leukotriene receptors are presented and hypotheses on the mechanisms of action and transduction are discussed.

A specific radioreceptor assay for leukotriene C4 and the measurement of calcium ionophore-induced leukotriene C4 production from human leukocytes

A highly specific radioreceptor assay (RRA) for leukotriene (LT) C4 using BC3H-1 cell membrane as a source of LTC4 receptors was developed and demonstrated its use in the measurement of calcium ionophore A23187-induced LTC4 production from purified eosinophils, neutrophils, and mononuclear cells. Unlabeled LTC4 competed for the specific [3H]LTC4 binding to the BC3H-1 cell membranes in a dose-dependent manner. Under the experimental conditions used in this study, the calculated IC50 value of unlabeled LTC4 was 27.2 +/- 1.2 nM (n = 5). The sensitivity of the method for LTC4 was 0.6 pmol. The cross-reactivities of LTD4, LTE4, and FPL 55712 were negligible. The recovery of the exogenously added LTC4 with eosinophils was greater than 90% in both the presence and the absence of calcium ionophore A23187. Calcium ionophore induced 73.0 +/- 17.0 ng of LTC4 production/10(6) eosinophils (n = 8), and this was about 20-40 times more than those from neutrophils and from mononuclear cells.