| "Spleen avers to dampness" is an important physiological characteristic of spleen in traditional Chinese medicine (TCM) viscera manifestation theory. According to TCM "correspondence between man and nature" theory, human beings are always affected by the natural factors, and thus can produce corresponding adaptive changes within human body. "Spleen corresponds with the late summer" was one of this theory. It means that the transportation and transformation function of the spleen in TCM has different physiological and pathological states between the humid later summer season and other seasons, and that it can be affected by dampness in the environment Abundant researches have revealed that, this function of spleen in TCM is closely associated with function of digestive tract. And previous study also founded that it is jejunum and ileum in the gut that has the same changing pattern with the late summer, which is characterized by high humidity. It thus indicates that jejunum and ileum has the closest relationship with spleen in TCM. However, the fact that there are many uncontrollable factors in natural environment makes the founded relationship cannot be fully explained. Therefore, this study aims to objectively prove the relevance from the perspective of "corresponding between man and nature" through observing normal rat intestine (jejunum, ileum and colon) under both high-humidity conditions with different temperature states (high temperature, normal temperature, and low temperature) and different moisture states (high humidity, normal humidity, and low humidity) accompanied by high temperature through artificial environment simulating with strictly controlled illumination.Currently, studies have found that intestinal melatonin and immune function play an important role in maintaining the health of human body, and are closely associated with the onset of intestinal diseases. Thus, in this study, intestinal melatonin and immune factors were selected as observing indices. 1 ObjectiveTo explore the role of wet factor in leading to different melatonin production and immunity of intestinal segments and to provide experimental basis for the connotation of "spleen avers to dampness" theory in TCM and the mechanism of "wet inclines to be trapped in spleen" by observing the influence of artificially simulated humid environment with high temperature, normal temperature and low temperature respectively as well as hot environment with high humidity, normal humidity and low humidity respectively on intestinal melatonin generation and immune function in different segments of normal rats, and comparing them with normal rats raised in simulated environment with normal humidity and temperature.2 Methods2.1 Literature reviewModern biological researches of six exogenous pathogens in TCM etiology and theories and researches related to intestinal mucosal immunity are concluded through literature study and logical analysis2.2 Experimental researchLevels of melatonin, activity of its rate-limiting enzymes, AANAT and HIOMT, and contents of immune factors, IL-2 and IL-10, in different gut segments under conditions of different humidity and temperature through artificial environment stimulation were observed. 2.2.1 Group:36 male SD rats (aged 7 weeks, weighted 240±10g) were randomly divided into 6 groups, namely normal humidity and normal temperature (NN, control) group, high humidity and high temperature (HH) group, high humidity and normal temperature (HN) group, high humidity and low temperature (HL) group, normal humidity and high temperature (NH) group, low humidity and high temperature (LH) group, with 6 rats in each group after adaptive raising (relative humidity (RH):60±2%, T:22±1℃)forl4 days.2.2.2Methods:artificial environment stimulating:manual climatic boxes in which rats of the six groups were raised were set respectively at:NN(RH:60±2%,T:22±1℃), HH(RH:90±2%,T: 30±1℃), HN (RH:90±2%, T:22±1℃), HL (RH:90±2%, T:13±1℃), NH (RH:60±2%, T:30±1℃),LH (RH:30±2%,T:30±1℃). Rhythm of illumination in all groups were set at day time of 12 hours and night time of 12 hours, and illumination rate were 3000Lx. Rats of each groups were raised in the set manual climatic boxes for 24 hours a day,14 days in total, during which standard diet and water were given. Then, all segments of jejunum, ileum and colon were excised for detesting levels of IL-2, IL-10, melatonin and activity of AANAT and HIOMT in each segment by ELISA.3 Results(1) Jejunum segment:compared with control group, the change of AANAT activity is not obvious (P> 0.05) in all groups with high humidity or high temperature, but levels of IL-2, IL-10 and MT and activity of HIOMT increased, and among them the MT content and HIOMT activity increased significantly (P<0.05 or P<0.01). Obviously, levels of IL-2 and IL-10 in HH group were the highest either among all groups with high humidity condition or among all groups with high temperature condition, and were significantly different from those in control group (P< 0.01).(2) Ileum segment:Among all groups with high temperature, animals in NH group presented with the lowest IL-2 and MT levels, lowest HIOMT activity and highest AANAT activity, all of which were significantly different from those in the control group (P<0.01, P< 0.01. P<0.05. P<0.01). Besides, there were significant difference in levels of Ⅱ.-2 and MT. and activities HIOMT between NH group and other groups with high temperature, and the AANAT activity in the NH group was also significantly different form that in HH group. As for IL-10 level, all groups with high temperature were higher than the control group and the increase in HH and LH group were statistically significant (P<0.01).(3) Colon segment:within all high humidity groups, the highest contents of IL-2 and IL-10 and activities of AANAT and HIOMT, and the lowest MT level appeared in HL group, with significant differences of all indices above from those in control group (P<0.01 or P<0.05) and significant differences (P<0.01 or P<0.05) of indices including IL-2 and MT content, and AANAT and HIOMT activity compared with HN group (P<0.01 or P<0.05). 4 Conclusion(1) Outside environments with different humidity and temperature conditions exert different influence on the immune function and melatonin production of different intestinal segments in rats. Specifically, both wet environment and hot environment can greatly influence immunity and melatonin generation of rats’jejunum by significantly improving the IL-2, IL-10 and MT levels and HIOMT activity. And the results that under environment of high temperature and humidity, levels of IL-2, IL-10 in jejunum were the highest compared either with those under other high humidity conditions, or with those under other hot environments show that high-humidity environment combined with high temperature has the strongest impact on immune function of jejunum in rats; As for colon, the change of temperature under wet condition is the major factor that results in changes of colon immune function and melatonin production, and the cold and damp condition (known as cold-dampness pathogen invasion in TCM) has the greatest influence; And in terms of ileum, immunity and melatonin generation are both influenced by high temperature and changes in humidity, and the change of environment temperature under wet environment also has significant effect on immune function and melatonin level of ileum..(2) Environment with high humidity and changes of humidity can strongly affect intestinal immune function and melatonin production, and the influence grows when temperature changes under wet condition.(3) Experimental data of the study, combined with results of early research, proves that from the perspective of "spleen avers to dampness", jejunum and ilium are in accordance with spleen in TCM and are closely associated with dampness in the outer environment. Besides, wet outside factor can exert influence on function of jejunum and ilium through changing their immunity and melatonin production. Thus the study provides modern biological proof for revealing connotation of "spleen avers to dampness" in TCM.
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