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[Change of the expression of adrenomedullin in lung and effect on contraction of isolated tracheal strip of asthmatic guinea pigs].

AIM
To study the formation and localization of ADM mRNA in lung tissues and investigate the effects of ADM on isolated tracheal strip contraction induced by histamine in asthmatic guinea pig.


METHODS
The guinea pigs (n = 22) were randomly divided into two groups of 11 each: asthmatic group and control group. The formation and localization of ADM mRMA were observed by in site hybridization. The effect of exogenous ADM on contractions of isolated tracheal strip of the asthmatic guinea pigs to histamine was examined.


RESULTS
There were strong positive expression for ADM mRNA in airway epithelial cells (AEC), smooth muscle cells (ASMC) in asthmatic group. The control group showed significantly decreased number of ADM mRNA positive cells in lung tissues. From 10(-11) mol/L to 10(-7) mol/L, ADM may cause concentration depend pentiation of the isolated tracheal strip contraction induced by histamine of asthmatic group which was higher significantly compared the control group (P < 0.05). 10(-8) mol/L ADM reached the maximal relaxation, with the increasing of ADM, neither asthmatic nor control group can increase the relaxation.


CONCLUSION
There is ADM mRNA overproduction in AEC and ASMC and exogenous ADM may inhibit isolated tracheal strip contraction induced by histamine of asthmatic guinea pig, which may contribute to airway inflammation and hyperresponsiveness in asthma.