Comparative Studies On The Histological Structures, Location Of Biological Active Substances And Antibacterial Effects Of The Extract Of The Skin Of Three Frog Species

As a great variety of amphibians, their skin have great amount of peptides, they have become the gigantic resource.The article takes Rana nigromaculata; Rana rugulosa; Rana catesbeiana as representative to initial investigate the value of different frogs'skin. The histological parameters of the skin of Rana nigromaculata,Rana rugulosa and Rana catesbeiana have been studied using the H.E staining and V.G collagen staining methods.The histological structures of the skin of three frog species are similar, but the absolute skin thickness, the relative skin thickness of each histological stratum and the gland's densities are significantly different at different body positions for different species.Generally,the skin of Rana rugulosa is the thickest one (0.44~0.68 mm),while Rana nigromaculata is the thinnest (0.19~0.38 mm);the relative thickness of epidermis at most positions of Rana nigromaculata(15.1～22.6%) is thicker than that of the Rana rugulosa (10.9～17.7%) and Rana catesbeiana (9.9～21.8%);the relative thickness of collagen fiber stratum in Rana rugulosa (59.9~68.7%)and Rana catesbeiana(51.6~75.3%) is larger than that of Rana nigromaculata(44.4~69.0%). The density of granular glands and mucous glands at most positions of Rana nigromaculata (4.5~23.1mm-2; 8.9~25.3mm-2) and Rana rugulosa (54.1~152.2mm-2; 68.6~127.5mm-2) are higher than that of Rana catesbeiana (1.4~10.8mm-2; 16.8~39.3mm-2). Then the distribution and density of five types of gastrointestinal hormone immunoreactive cells in the skin of three frog species have been investigated using the Streptavidin Peroxidase(SP) immunohistochemical methods.Five types of gastrointestinal hormone immunoreactive cells are detected in the dorsal skin, ventral skin and mucous gland epithelium of Rana nigromaculata; Rana rugulosa; Rana catesbeiana, including 5-hydroxytryptamine (5-HT), gastrin (GAS), glucagon (GLU), pancreatic polypeptide (PP) and somatostatin (SS). All types of gastrointestinal hormone immunoreactive cells except PP immunoreactive cells are detected in both dorsal and ventral skins'granular glands in Rana nigromaculata and Rana catesbeiana, while none these five cells are detected in the same position of Rana rugulosa. The density of the same immunoreactive cells have the certain differences in the same parts of different species of frogs and different parts of the same frogs. The antibacterial effect has been studied using the disc diffussion methods and compare the effects of three frogs'skin extracts acting on Escherichia coli; Staphyloccocus aureus Rosenbach; Bacillus subtilis.The results indicate that the MIC of the concentrate acting on Escherichia coli is 1.25mg/ml,which is extract on Rana rugulosa's skin using the ether provocation methods,while the other concentrate acting on Escherichia coli is 2.50mg/ml,which is extract on Rana rugulosa's skin using the methanol ether provocation methods,too.There are no notable effect of Rana nigromaculata; Rana catesbeiana's skin extract. On a conclusion, most parts of Rana nigromaculata's body skin are thick relatively, which can against loss of water well.It may has difference of texture on leather manufacture.The back skin of Rana rugulosa should be smoothed on leather manufacture, while the back skin of Rana catesbeiana should be grinding.There have potential value of Rana nigromaculata; Rana rugulosa in the way of extracting collagen. Five types of gastrointestinal hormone immunoreactive cells are detected in the skin and mucous gland epithelium of Rana nigromaculata; Rana rugulosa; Rana catesbeiana,while there are difference on the same of granular glands.It offers new consideration of frog species'skin extract on clinical application.And Rana rugulosa has advantage in the way of skin extracting antimicrobial peptides. Base on the three frogs'skin have same commonness on histological structure,location of biological active substances and the extract's antibactrtial effects,while there are interspecific difference,it is accommodated of their respective habitation and specific physiological structure.It can be properly exploited while makes the best of each frogs'potential advantage.