| Abstrakt: |
The relationship between rat peritoneal mast cell activation and inactivation (desensitization) was studied for a variety of stimuli acting via IgE and IgG receptors on the cell surface. Anti-IgE, antigen (ovalbumin), anti-IgG1, anti-IgG2a and dimers, trimers and higher oligomers of IgE were used to induce histamine release from rat mast cells. All produced similar characteristics of cell activation, with a rapid rate of histamine release from the cells, release being 90% complete within 5 minutes and with calculated doubling times between 21.6 +/- 3.6 s (+/- SEM) for ovalbumin and 93.0 +/- 18.6 s (+/- SEM) for anti-IgG1. The characteristics of inactivation, however, varied with the releasing agent used. Of all the stimuli used only ovalbumin showed a rapid rate of desensitization (t 1/2 = 330 +/- 34.8 s) which correlated with the cessation of histamine release. The other stimuli showed slow rates of desensitization (t 1/2 between 1068 +/- 40.2 s for dimer and 3576 +/- 660 s for anti-IgE) even though the rate of release was rapid. Thus, although these stimuli are thought to be stimulating the cells by cross-linking of either IgE or IgG receptors, the difference in subsequent response of the cells would indicate that the transduction mechanism bringing about release can distinguish between these various stimuli. Also, it seems that the idea that duration of histamine release is determined by the rate of desensitization may need revising as with most of these stimuli, release has terminated when the cells are still in a fully activated state. |
