[Sephadex induced inflammation in rats (author's transl)].

QUESTION: A single s.c. injection of Dextran is very suitable in producing an inflammatory response in the rat. The Dextran edema has become a standard method. It seems not uhlikely that Sephadex, the Dextran gel widely used in the gelchromatography may have a similar effect. Sephadex, because of its physiochemical properties, would offer some advantages in the studies of inflammatory reactions. But first of all the following questions have to be answered: 1. Does one single s.c. injection of Sephadex produce an inflammation at all and what are the characteristics on the microscopical level? 2 Does it make any difference if Sephadex of different types are injected?
MATERIAL AND METHODS: Male and female Wistar rats (100-250 g) in groups of 5 animals each. Diet: Rat pellets "Tagger" and tap water ad libitum. Sephadex (Pharmacia Fine Chemicals) of the types G-25 m, G-50 m, G-100, and G-200 were soaked in 0.9% saline for the prescribed time and afterwards preserved until the Sephadex gel had settled on the bottom of the vessels. 1 ml of this Sephadex gel slurry each were subcutaneously injected to the shaved dorsal skin of the rats (right below). At different intervals (3, 6, 24 and 72 hours: 6, 14, 20 and 28 days) the Sephadex depot and the surrounding tissue were exstirpated and examined histologically. During all the procedures the animals were subjected to ether anesthesia. From the tissue samples frozen sections (Kryocut, -30 degrees C) were prepared and stained with hematoxylin and eosin or after van Gieson. Moreover, several preparations were stained after Pappenheim and Weigert (fibrin) or with PAS and toluidine blue. For recording of probable differences in the effect of the particular Sephadex types always 2 values were determined histometrically. The number of exudate cells emigrated between the Sephadex beads within the area of an ocular-net (edge length 1.66 mm) were counted at 500-fold magnification. Furthermore, the number of eosinophils was determined by the technique. However, because of poor occurrence the eosinophils were counted in 10 fields of view. Tests with Sephadex G-10 were omitted as preliminary tests had shown that it is not suitable for s.c. injections because of its gritty consistency (due to poor soaking properties).
RESULTS: One single s.c. injection of Sephadex in the rat induces an acute inflammation. The exudative phase marked by a massive leucocytic infiltration (especially PMN leucocytes) is followed by the appearance of mononuclear leucocytes and fibroblasts after the 2nd day. The inflammation declines within approximately 3 weeks. Thereafter the Sephadex depot is encapsulated by a fibrous tissue. A chronic inflammation was never observed. In the microscopical aspect of the inflammation produced by the different types of Sephadex were detectable. The Sephadex lying in the tissue does not change its original shape, it is insoluble and is not disintegrated. The size of the particles prevents the transport into the blood or lymph vessels...