Antiallergic activity profiles in vitro of RHC 3164 and related compounds. I. A lack of correlation between inhibition of cyclic nucleotide phosphodiesterases and antigen-induced release of histamine from rat mast cells

A series of 26 compounds belonging to the chemical class of (1,2,4)triazolo(4,3-a)-quinoxaline-1,4-diones have been investigated for their antiallergic activities in 3 in vitro models of anaphylaxis. Effects of these and other known antiallergic agents on cyclic nucleotide phosphodiesterases (cNUC-PDE) from purified rat mast cells have also been investigated. 18 compounds were potent (I50 less than or equal to 45 microM) inhibitors of antigen-induced release of histamine (AIR) from rat mast cells (RMC), 3 compounds inhibited anti-IgE-induced release of histamine from human basophils (I50 less than or equal to 25 microM) and none of the compounds significantly affected AIR from guinea pig lung slices. 13 of the compounds were more potent than theophylline as inhibitors of cyclic AMP-PDE and/or cyclic GMP-PDE from RMC. Parallel concentration-response curves for the inhibition of cyclic AMP-PDE and cyclic GMP-PDE indicated that these compounds probably interact with enzyme in the same manner. Paired regression analysis of the I50 values for inhibition of AIR and cNUC-PDE from RMC by these compounds revealed no statistically significant correlation between the inhibition of AIR and inhibition of cyclic AMP-PDE or cyclic GMP-PDE. We conclude: (1) some of these compounds are potent inhibitors of immunologic release of histamine from RMC with an in vitro activity profile similar to that of DSCG, and (2) inhibition of cyclic AMP or cyclic GMP hydrolysis by cNUD-PDE by these compounds, DSCG, and 6 known antiallergic agents is not the biochemical mechanism by which they inhibit AIR from RMC.

Antiallergic activity profiles in vitro of RHC 3164 and related compounds. II. Comparison of RHC 3164 with disodium cromoglycate

RHC 3164 has been investigated for its antiallergic activities in 3 in vitro models of anaphylaxis. RHC 3164 was 6 times more potent than DSCG as an inhibitor of antigen-induced release of histamine (AIR) from rat mast cells (RMC) and had an activity profile identical to that of DSCG in the following respects: loss of inhibitory activity with increasing preincubation time, tachyphylactic properties, cross-tachyphylaxis to DSCG, and inability to inhibit nonimmunologic release of histamine. Neither RHC 3164 nor DSCG had any effect on immunologic release of histamine from human basophils or guinea pig lung slices. We conclude that RHC 3164 is a potent inhibitor of immunologic release of histamine from RMC with a mechanism of action similar to that of DSCG.

Physiological and mutational protein variations in the ciliary membrane of Paramecium

The proteins in the ciliary membrane of wild-type and mutant Paramecium tetraurelia are examined with SDS and IEF gels. Over 80% of the proteins in the ciliary membrane belong to two groups: the immobilization antigen (I-Ag), which is a 220-280 kD surface protein, and a set of at least four integral proteins slightly over 40 kD (the 40 k), most of which focus near pH 4.0 (the acidic 40 k). Variations of the I-Ag in its apparent molecular weight appear spontaneously in different clones of the same strain and can be triggered by changing the culture temperatures. We discovered that the members of the acidic 40 k family also vary in their relative proportion. Furthermore, the variations in I-Ag and those in acidic 40 k are tightly coupled. The concerted changes suggest a co-regulation in the synthesis of these proteins. The ciliary membranes of 20 mutants of 11 complementation groups known for their behavioral and electrophysiological defects are examined. Coupled variations of I-Ag and acidic 40 k among clones, similar to those of the wild type, are seen. Besides the I-Ag and the acidic 40 k, this membrane has over 60 other species of proteins, most of which are invariant. Shifts in the isoelectric points of two of these minor proteins have been correlated with two different mutations, 'fast-2' and 'paranoiac A'. No electrophoretic shifts can be correlated with the 'pawn B' mutation as found by Merkel et al. [35].

Isolation and characterization of antigenic components of rat glomerular basement membrane

(1) A method was developed to separate normal rat glomerular basement membrane (GBM) into six components by collagenase digestion, urea extraction, and gel filtration.(2) Treatment of rat GBM with collagenase did not alter nephrotoxic antigenicity of the membrane. Further proteolytic digestion with pronase resulted in loss of ability to elicit nephrotoxic antibody. Rat GBM prepared by mild alkali treatment still retained nephrotoxic antigenicity.(3) Antibodies against isolated components, except two which were retained on Sephadex G-75, localized to GBM and induced proteinuria in rats. One of the components retained on Sephadex G-75 produced localizing, non-nephrotoxic antibodies, while the other produced no localizing antibodies. Multiple antigens and common antigenic determinants among membrane components were demonstrated by gel double diffusion.(4) A specific nephrotoxigenic antigen from rat GBM was characterized as a macromolecular glycoprotein containing 10.7% carbohydrate in the form of galactose, mannose, sialic acid, glucosamine, and galactosamine. On analytical ultracentrifugation in Tris buffer, it gave two peaks with sedimentation constants of 5.93 and 3.49 S, while in 8 M urea it appeared as a single symmetrical peak with lower sedimentation constant (1.33 S) suggesting the presence of aggregate forms of the glycoprotein.(5) Dog GBM and collagenase-solubilized components elicited antibodies which localized to rat GBM but failed to produce proteinuria. Antibody to tendon collagen also localized to rat GBM but had no nephrotoxic effect on normal rats. Antibody to collagen fragments obtained from collagenase digestion failed to localize on rat GBM but still cross-reacted with tendon collagen in gel diffusion.