Histologische Untersuchungen über die Wirkung von Solanum Melongena auf die cholesterininduzierte Atheromatose des Kaninchens im Mittel- und Langzeitversuch: Effect of Solanum Melongena on experimental atheromatosis

Abstract

Question: In earlier studies [see literature (2, 20, 21, 22)] observations concerning the effect of Solanum Melongena (Sol. Mel.) (violet egg plants) on experimentally induced atheromatosis in rabbits were reported. This study aims to investigate histologically the effect of Sol. Mel. on experimental atheromatosis in mean-term (2–4 weeks) and long-term (8–12 weeks) tests. Materials and methods: For details of the test arrangement see Auböck and Mitschek, Exp. Path. 9, 323–335 (1974). From one portion of the material for histological examination cryostat sections were prepared, the other portion was fixed in Bouin's solution or in Baker's formol and paraffin-embedded at 58–60 °C (cross sections of the aorta). The specimens were stained as follows: erythrosin in conjunction with haematoxylin; aqueous or alcoholic solutions of toluidine blue ( pH 3.5 to 5, and 7); methylene blue ( pH 2.5 to 5, and 8); alcian blue ( pH 2.5); Schiff-PAS; alcian blue and PAS in combination; Sudan III; elastica-van Gieson (blue) and Weigert's iron haematoxylin. For demonstration of mucopolysaccharides (MPS) the control sections were pretreated in a 10% Takadiastase solution for 10 minutes at 37 °C. In liver sections PAS-reactivity was additionally blockeed by dimedone (cyclohexanedione) for elective demonstration of glycogen. The tissue sections were studied in transmission —, incident- and dark field illumination. Results: Lipid deposits as demonstrated by surface preparation technique could not be seen in paraffin sections after just one day. In the vascular wall histological changes were earliest visible after 10 to 14 days (enlargement of the subendothelial space and honeycombed edema with fine dispersed lipids). At this stage a “haematoxylin-effect” did yet not develop. Sometimes these alterations were also present in the upper layers of the media. They always first occured in the aortic arch. At this time the Sol. Mel.-treated animals of group II only occasionally developed superficial edemas. Enlargement of the media with edematous infiltration and loosening of the elastic fibers was similar in both cases (figs. 1a and 1b). Fatty degeneration of the liver was already macroscopically visible on day 14; in untreated animals of group I it was more expressive than in group II (figs. 2a and 2b)— this likewise applied to the cholesterol content (figs. 3a and 3b). After about 30 days in group I the earliest macroscopically visible plaques occured prevailingly in the aortic arch and in the thoracic aorta. The development of such small foam cell plaques could be continously observed with a hand lens (fig. 4a). In group II, however, it was not possible to observe any development of plaques with a hand lens, persistence of edemas was demonstrable with such (fig. 4b). Within these, fine dispersed droplets were present (fig. 5) but exact localization was only possible by electron microscopy [see literature (2)]. Whereas we often saw small foam cell plaques also in the arteries of the lungs of animals of group I we never observed them in the Sol. Mel.-treated rabbits of group II. After 40 days sudanophilia decreased following inset of fibril formation within the intima plaques; the haematoxylin-effect, however, not only persisted but was even intensified (fig. 7a) and had the typical appearances of coagulated milk. At the same stage intima plaques developed in the abdominal aorta as well. By the l0th week the internal vascular surface of untreated animals was coated with 1- to 1 1/2-mm-high yellowish-white foam cell plaques with silky gloss. It must be mentioned that in animals of the test series fed an intermittent cholesterol diet necroses and fibril formation in the intima were much more expressed than in animals continously fed a cholesterol diet for the same period. Moreover, the lipid deposits extended beyond the lamina elastica interna into the upper layers of the media (colour plate, fig. I). Between day 30 and day 60 in the Sol. Mel.-treated animals of group II regression of edemas was associated with thickening of the subendothelial and subintimal layers whereas loosening of the deeper layers continued. After several months' exposure of the animals to extreme conditions and intermittent normal diet pinhead-like white patches were also observed in the animals of group II in the aortic arch and in the aortic branches. They were identified as persistent foam cell plaques which did not enlarge even after 8 months. They never necrotized. In group I increase in the amount of acid mucopolysaccharides (MPS) was observed simultaneously with the development of edemas and formation of intima plaques. In young plaques with abundant cells pH 5-orthochromasia prevailed after toluidine blue staining (colour plate, fig. III) whereas in older plaques red metachromasia prevailed with enhanced fibril formation (colour plate, fig. III). The high amount of neutral MPS in old plaques was most impressive following PAS-staining (colour plate, fig. IV). In the animals of group II increase in the amount of MPS became more noticeable earliest on day 14 at the earlies and reached its maximum by day 40. The development of foam cell plaques and increase in the amount of MPS were studied systematically during their temporal course. In both groups fatty degeneration of the liver was associated with a loss of glycogen which was markedly higher in untreated animals when compared with those fed Sol. Mel. On the basis of recent observations and of these studies it can be summarized that the development of experimental atheromatosis in rabbits was inhibited to a great extent by the administration of Sol. Mel. in short-term tests. Likewise in mean-term tests (2–4 weeks) Sol. Mel. inhibited the development of foam cell plaques to a certain degree. In long-term tests (8–12 weeks) the vascular changes were also reduced by administration of Sol. Mel., however, less noticeably when compared with the results in mean-term tests (2–4 weeks). In animals fed an intermittent cholesterol diet necroses and calcifications never occured when they were treated with Sol. Mel. (For comparison see test results of group I — no Sol. Mel.). In the whole, daily administration of Sol. Mel. had an inhibitory effect on the development of cholesterol-induced atheromatosis, however, it did not prevent it totally. Occurrence of vascular edemas likewise was reduced by Sol. Mel. but hitherto it was not possible to suppress them completely.