BERCENDORFF, A. and B. UVNAS. Storage of 5-hydroxytrypfamine in rat mast cells.Evidence for an ionic binding to carboxyl groups in a granule heparin-protein complex. Acta physiol. scand. 1972. 84. 320-331.Rasophil granules were isolated from rat peritoneal and thoracic mast cells. T h e granules were depleted of their endogenous Hi and 5-HT and the amine storing properties of these depleted granules were studied. T h e influence of pH, the uptake capacity, the releasing action of sodium ions and the competitive uptake of Hi and 5-HT by the granule stores all support the hypothesis that the granule stores have the properties of a weak cation exchange resin. It appears that 5-HT release, as we previously showed for Hi-release. is due to a cation exchange occurring on mast cell degranulation, hhen the amine-containing granules become exposed to cations of the extracellular milieu.20 min in order to precipitate the granules. Usually granules were collected from 30. lo6-40. loG mast cells (15-20 rats) for each experiment. For details of the isolation procedure see Uvnas et aZ. (1970).3---723003. Acfa physiol. scand. V a l . 84: 3

Basophil granules were isolated from rat peritoneal and thoracic mast cells. The granules were depleted of their endogenous Hi and 5‐HT. The uptake of Hi, 5‐HT, TrpA, PhEA, TA, DA, NA, ACh, Na and Ca (for abbreviations see page 215) by the depleted granules, the release of Hi from Hi‐recharged granules by Ca, Na and K and the competition between NA and Hi, ACh and NA, ACh and Hi for the granule storage sites were studied. The results support the hypothesis that these granule stores have the properties of a weak cation exchange resin. Furthermore it was found that amphetamine and ephedrine competed with NA for the storage sites The results indicate an unspecific granule storage of cations—organic and inorganic—differing only in their affinities for the binding sites.

No abstract

Mast cells isolated from rat peritoneal and pleural cavities were incubated in vitro with radioactively-labelled histamine (Hi), 5-hydroxytryptamine (5-HT), dopamine (DA), noradrenaline (NA), tyramine (TA), phenylethylamine (PhEA), trptamine (TrpA), ephedrine (Eph) or amphetamine (Amph). All these amines were taken up by the mast cells. The dose-response curves for the compound 48/80-induced release of endogenous Hi and for the various amines taken up by the cells were compared. The release curves for Hi, 5-HT, DA, NA and TA were found to be similar to that for endogenous Hi, while those for PhEA, TrpA, Eph and Amph were different from that for endogenous Hi. The uptake of Hi, 5-HT, DA, PhEA, TrpA and Eph into granules in mast cells was studied. Membrane-bound granules were obtained by sonication of mast cells incubated with the respective amine, followed by differential contrifugation. The amine content of these granules was then measured. Hi, 5-HT and DA were found to be mainly localized to the granules, while a smaller proportion of the PhEA, TrpA and Eph was found there, the rest being located extragranularly. The present results suggest that, when taken up by rat mast cells, even amines which are not endogenous to the cells are stored in the same way as the endogenous amines Hi and 5-HT.

Biologically active substances, for example histamine and heparin, are localised in the mast cells, where they are found in the granular fraction. The rat mast cell also contains 5-hydroxytryptamine. Granules from rat mast cells have been shown to be very useful in studies on release and uptake mechanisms since they are relatively easy to isolate and furthermore are very slightly soluble in water and isotonic salt solutions. The granules consist of a heparin-protein complex to which histamine is bound.The uptake and release mechanism for histamine has been shown to be pH-dependent and it has also been shown that cations are capable of replacing histamine. These results suggest that the binding between histamine and the heparin-protein complex is electrostatic and that it is probably a binding to weak acid groups in the complex. One could perhaps compare the granules to a cationexchanger of the carboxylic type.A recent investigation on the specificity of the binding has shown that other amines such as 5-hydroxytryptamine, adrenaline, noradrenaline, dopamine, tyramine, phenylethylamine and acetylcholine can be taken up by the granules. Thus the linkage between histamine and the granules does not seem to be specific. There are certain differences however in the affinities of the different amines for the granular binding sites. The uptake of the other amines also seem to be pH-dependent and it is possible to release them with sodium. Therefore one would expect the binding between the amines investigated and the heparin-protein complex to be the same as for the naturally occurring histamine.