An automated fluorimetric assay for the simultaneous determinations of histamine and 5-hydroxytryptamine released from rat mast cell preparations

The effect of adrenocorticotropin on histamine and 5-hydroxytryptamine secretion from rat mast cells

Characteristics of histamine (Hi) and 5-hydroxytryptamine (5-HT) release from rat peritoneal mast cells in response to the polypeptide adrenocorticotropin (ACTH) were studied. During a 15 min incubation at 37 degrees C, ACTH evoked Hi as well as 5-HT release from rat mast cells at concentrations of 1 X 10(-4) M-1 X 10(-3) M. The release was dose-dependent and very rapid. After 15 sec the amount of the amines released was the same as after 4.5 min. In most experiments, the percentage of Hi release was slightly but significantly higher than the percentage of 5-HT release. Hi and 5-HT release induced by ACTH also took place in a calcium-free medium. However, the release of the amines was decreased when calcium was omitted. Comparison of the effects of ACTH, compound 48/80 and substance P on mast cell secretion showed that ACTH is about 100 times less active then substance P which was in turn about 100 times less active than compound 48/80. When both ACTH and compound 48/80 were used together as liberators , the release was significantly higher than with either liberator alone. Our results indicate that there are receptor sites for the endogenous polypeptide ACTH on the mast cell membrane which mediate Hi and 5-HT release. This release was found to resemble that evoked by the basic secretogogue compound 48/80 but in some aspects to be different from that evoked by substance P.

A high-sampling-rate automated continuous-flow fluorometric technique for the analysis of nanogram levels of histamine in biological samples

An automated continuous-flow technique of the modified fluorometric method of Shore was devised to obtain a high sampling rate (60/h) and a sensitive measurement of the histamine content of biological samples. The volumes of samples range from 50 to 500 microliter. A linear relationship is obtained from 0 to 5 micrograms/ml (histamine base) with a good specificity. The limit of detection is 25 pg (actual amount). The coefficient of variation is less than or equal to +/- 5% for concentrations of less than 2 ng/ml and from +/- 0.2 to +/- 2% for higher concentrations. With this technique more sensitive, more specific, and twice as fast as similar ones, histamine content in 350-400 unknowns can be measured routinely in a working day. It has been used for more than 4 years and has proven to be a reliable and useful tool for the numerous research studies in which histamine is involved: immunology, allergy, pharmacology, dermatology, cancer, nutrition.

Compound 48/80 and substance P induced release of histamine and serotonin from rat peritoneal mast cells

The effect of substance P and compound 48/80 on histamine and serotonin release from not isolated and isolated mast cells have been compared in experiments in vitro. The response of not isolated and isolated mast cells were virtually identical. The release of both amines, in response to 48/80 and substance P, was dose-dependent. The percentage of histamine released by 48/80 was significantly higher than the percentage of serotonin, the difference being higher at lower concentrations of compound 48/80 after 15 min of incubation. Substance P also showed a tendency to higher efficiency for histamine than for serotonin release. In contrast to 48/80, the dose-response curves for histamine and serotonin release were parallel. These results support the view that the ratio between histamine and serotonin release depends on the liberator used. They also showed that this ratio can depend on the concentration of the agent inducing secretion. The results indicate that substance P as well as 48/80 act rather selectively as histamine liberators and that there is some difference in releasing properties of 48/80 and substance P.

In vitro cell perfusion. I. System for continuous observation of cells and analysis of perfusion fluid suitable for isolated mast cell and macrophage studies

A system is described in which cells are perfused continuously with appropriate medium while simultaneously recording any change in cell morphology together with assay of released products (enzymes and mediators) following immunologic or non-immunologic perturbation. The released products in the perfusate are monitored continuously by automated fluorimetric assay procedures. The system is particularly applicable to investigate or toxicological studies of isolated mast cells or cultured macrophages.