The Study Of Antagonistic Action For Exogenous CGRP To ET-1 Induce Newborn Rat Pulmonary Hemorrhage

PrefacePulmonary hemorrhage of newborn (PHN) is a fatal symptom of many kinds of neonatal disease. It always present before die and induced mainly by hypoxia, infection and hypothermia. Our previous study has confirm that hypothermia and hypoxia followed by rewarming and reoxygenation can induce NPH, exogenous endothelin-1 (ET-1) can induce PH, exogenous calcitonin gene-related peptide ( CGRP) may can antagonist action of pulmonary hemorrhage induced by ET-1. CGRP is a potent vasodilator and distribute in the central and peripheral nervous systems widely. predominantly expressed in the pulmonary neuroendocrine cells and nerve fibers. The dilatation of lung vessel induced by CGRP is potent and permanence and important to support low tension for lung vessel. ET-1 is the strongest contractor and has two subspecies receptor in lung: ETAand ETB ETA distribute in the smooth muscle of vessel and bronchial and contraction. In many clinic study suggest that ET-1 is closely to hypoxic pulmonary hypertension. There some evidences suggest antagonist between CGRP and ET-1 each other. Our study hope to know whether pretreatmenl with exogenous CGRP can antagonist pulmonary hemorrhage of newborn rat induced by exogenous ET-1.Materials and MethodsForty Wistar newborn rat (age 4 ~5d) were randomly divided into saline control group ( group A) and experiment group ( group B ~ D) , each group have ten rat; Concentration of CGRP were 6. 7 x 10-10 mol/L (group B) ; 6. 7 x 10 -8 mol/L ( group C ) ; 6. 7 x 10-6 mol/L (group D) ; Dripping different concentra-tion of CGRP by tracheal intubation then sacrificed the rats after 2 hours and observe the morphological change in the lung of different groups: grade I normal lung, grade II pulmonary edema, grade III spotted pulmonary hemorrhage, grade IV local pulmonary hemorrhage, grade V diffuse pulmonary hemorrhage and to judge if CGRP can cause pulmonary hemorrhage.Repeat the first step and after exogenous CGRP precondition 1 hours and each group dripping exogenous ET-1; Concentration of ET-1 was 4 x 10 ~ mol/ L, then sacrificed the rats after 2 hours and observe the morphological change in the lung of different groups: as the methods 1; to assay and compare the expression of ET-1 and eNOS in the lung of different degree in pulmonary hemorrhage by the method of immunohistochemistry.Results1. The effect to pulmonary hemorrhage in groups of different concentration (6. 7 x 10"1 mol/L -67 x 10-6 mol/L )CGRP was not significant difference between each others( P > 0. 05).2. The comparison of the degree of pulmonary hemorrhage: the degree of lung injury in the group E ,F ,G was more serious than in group H(P <0. 05) , there were no significant difference between group E ,F ,G (P>0.05).3. The comparison expression of ET-1 in the lung tissues by immunohistochemistry technology: the incidence of ET-1 positive was lower in H group than in the other group, there was significant difference between group H and group E ,F ,G(P<0.05).4. The comparison expression of eNOS in the lung tissues by immunohistochemistry technology: the incidence of eNOS positive was higher and stronger in H group than in the other group, there was significant difference between group H and group E ,F ,G(P<0.05).DiscussionOur study approve the exogenous CGRP can not cause pulmonary hemor-rhage and then confirm the exogenous ET-1 can induce pulmonary hemorrhage a-gain, but we can antagonist this action by precondition lung with exogenous CGRP( concentration was 6. 7 x 10 ~6 mol/L). We confer mechanism are.-1. Dripping concentration of exogenous CGRP was 6.7 x 10 ~ mol/L by tra-cheal intubation can depress the expression of ET-1 in lung and then antagonist the contraction of vessel and bronchia induced by ET-1.2. Dripping concentration of exogenous CGRP was 6.7 x 10-6 mol/L by tra-cheal intubation can increase the expression of eNOS in lung and then NO can vasodilator vessel and antagonist assemble of platelet. eNOS can antagonist the vessel contraction of ET-1.3. The exogenous CGRP can...