respiratory distress continues to account for significant 
 mortality and morbidity in the neonatal intensive care unit . at 
 birth ,
respiratory 
 distress syndrome ( rds ) in premature infants is caused by a 
 structural immaturity of lungs and the insufficient production of 
 surfactant and its incidence is inversely related to gestational 
 age .
the problems concerning to the respiratory system 
 prolonge the hospitalization period in the premature infants 
 .
endothelin ( et ) is a peptide of 21 amino acids in chain with two 
 disulfide bonds with three distinct isoforms : et-1 , et-2 , and et-3 
 .
endothelin causes isolated contraction of pulmonary 
 veins , vascular smooth muscle mitogenesis , myocardial cell 
 hypertrophy , positive innotropic and chronotropic effects , 
 bronchoconstriction , mucous secretion , cellular proliferation , and 
 inflammatory reactions .
hypoxia , stress , antidiuretic hormone , and the secretion of some mediators stimulate its 
 synthesis .
clinical investigations have shown increased plasma 
 concentrations of et-1 during rds and in case of pulmonary 
 hypertension of other origins .
but it is unclear whether et-1 is 
 actually responsible for the pulmonary hypertension , or the 
 increased et-1 plasma concentration is a result of the 
 pulmonary hypertension that originated otherwise [ 58 ] . also transforming growth factor beta ( tgf- )
is a family of 
 three isoforms that regulate cell growth and differentiation , 
 extracellular matrix sythesis cytokines production , and vascular 
 neogenesis .
the increase in tgf- precedes the development of pulmonary hypertension which increases circulating 
 et-1 levels in animals .
tgf- induces et-1 gene expression 
 and et-1 peptide synthesis in bovine pulmonary artery endothelial 
 cells [ 10 , 11 ] .
the cells responsible for increased et-1 
 sythesis during hypoxia are unclear , and short - term effects of 
 hypoxia raise plasma et-1 levels in animal models ; whether chronic 
 hypoxia would lead to different results is unknown .
experimental studies have suggested that et-1 plays an important 
 role in pulmonary vascular reactivity in neonatal rds .
there is 
 also an elevation of et-1 in tracheal aspirates from these 
 infants .
tgf- showed the strongest stimulatory effect on et-1 and gene transcription in vascular smooth muscular 
 cells .
there are few studies measuring et-1 and no study measuring tgf- by enzyme immunoassay with a very small 
 number of human premature newborns suggesting that et-1 is 
 elevated in rds .
the purpose of this present study is to evaluate the serum levels of 
 et-1 and tgf- in the newborns with respiratory distress 
 ( diagnosis as rds , as transient tachypnea ( rds-2 ) , and as 
 meconium aspiration syndrome ( mas ) ) , to investigate the 
 meaningfulness of the repetitive values of et-1 in the followup 
 of these diseases , and to determine the reflection of serum et-1 
 level on the mortality at the first six hours after birth .
in this study , newborns with respiratory distress hospitalized 
 into the newborn intensive care unit were included .
the study 
 group was evaluated by 100 newborns , 62 diagnosed as rds , 24 as 
 rds-2 , and 14 as mas within the last six months . moreover , a 
 control group was evaluated with 20 healthy newborns . for the 
 study ,
written permits were taken from the parents of each 
 newborn , as well as an approval of the regional ethics comittee .
the gestational 
 age of the newborns was determined according to the new ballard 
 score . according to the gestational age , newborns younger than 38 weeks were classified as premature and newborns 
 between 3842 weeks as mature .
after a detailed physical 
 examination , the newborns were investigated with respect to their 
 blood gases , complete blood count , full blood biochemistry , and 
 c - reactive protein levels , and their culture samples were taken .
moreover , first blood samples were obtained from all premature and 
 mature sick or healthy newborns in the first six hours after 
 birth .
the serum was collected into polypropylene tube and 
 centrifuged immediately and was stored at 70c . in 
 addition , repetitive blood samples were obtained at the third , 
 7th , 14th , and 28th day from the patients whom oxygen supply 
 continued .
these serums were also stored at 70c . then , 
 the samples were resolved and they were studied with elisa method 
 in the immunology laboratory .
plasma tgf- level was determined by capture elisa according 
 to the instructions of r & d systems using monoclonal antihuman 
 tgf- , r & d systems , inc ( usa ) . in brief ,
100 l 
 of the capture antibody was transferred to an elisa plate and 
 incubated overnight at room temperature .
after removal of the buffer , the 
 plates were blocked by adding 300 l of pbs containing 5% 
 tween 20 , 5% sucrose , and 0.05% nan3 to each well and incubated at room temperature for a minimum of 1 hour . 

100 l of blood plasma sample per well was added , the 
 elisa plate was covered with an adhesive strip and incubated 2 
 hours at room temperature .
100 l of streptavidin hrp ( r 
 & d systems , catalog # dy998 , 1/200 in appropriate diluent ) was 
 added to each well ; the plate was covered and incubated for 20 
 minutes at room temperature .
after subsequent addition of 
 substrate solution and stop solution ( both from r & d systems , 
 inc ) , the optical density of each well was determined within 30 
 minutes , using a microplate reader set to 450 nm .
et-1 
 was determined by an enzyme immunoassay ( quantiglo human et-1 , 
 r & d systems , inc , minneapolis , minn , usa ) .
the minimum 
 detectable dose of et-1 was 0.16 pg / ml , with intra- and 
 interassay coefficients of variation of 2.5 and 5% , 
 respectively .
moreover , in the differential diagnosis the 
 meaningfulness of the et-1 and tgf- values was 
 investigated using the scheffe and tukey post hoc tests , in the 
 followup , the differences of the et-1 levels were investigated 
 using the kruskal - wallis variance analysis . in all of the results 

the newborns comprimising the study group had a gestational age 
 between 2842 weeks . from all of the patients 62 ( 62% ) 
 newborns
of 
 24 newborns with rds-2 diagnosis 16 ( 67% ) were mature and of 
 14 newborns with mas diagnosis 11 ( 79% ) were mature . in the 
 control group , only 11 ( 55% ) newborns were mature 
 ( table 1 ) .
male predominance with a percentage of 
 61% was determined in the group with rds , and weight results 
 were considerably lower due to prematurity ( 1367  368 g ) .
plasma endothelin-1 and tgf- concentrations of the mature 
 newborns in the control group were measured as 0.77  
 0.56 pg / ml and 0.25  0.41 pg / ml , respectively , and 
 did not show a significant difference according to the 
 gestational age ( p > .05 ) ( figure 1 ) .
plasma endothelin-1 and tgf- concentrations of the 
 newborns with different diagnosis measured in the first six hours 
 of life are summarized in figure 2 . in the 
 description of the effectiveness of the treatment and in the 
 early determination of the prognosis plasma et-1 and tgf- 
 concentrations in newborns with mas diagnosis
were determined as 
 5.70  5.87 pg / ml and 3.75  1.94 pg / ml , and with 
 rds diagnosis were determined as 3.37  1.59 pg / ml and 
 2.05  0.98 pg / ml . according to the control group , plasma 
 et-1 and tgf- concentrations of the newborns with 
 respiratory distress were determined to be statistically higher 
 ( p < .05 ) . with the oxygen supply , it was observed that plasma et-1 
 concentrations of the newborns obtained in the first six hours of 
 life are desposed to decrease regularly in the following days 
 ( figure 3 ) . in the same way ,
plasma et-1 
 concentrations obtained in the first six hours and repetitive 
 plasma et-1 concentrations in the following days were 
 statistically higher in the newborns who died later compared to 
 the survivors ( p < .05 ) ( figure 4 ) .
respiratory distress is a major problem in the newborns and 
 different reasons cause this problem . among those , the most 
 frequent ones are rds ; a problem of premature newborns , and the 
 others are rds-2 and mas ; a problem of mature newborns . in this 
 study ,
diseases causing respiratory distress after birth in the 
 early period were evaluated , and rds was the most frequent ( 62% ) . endothelin-1 and
tgf- levels , the vascular factor , and 
 material of respiratory distress were investigated . in the 
 control and patient groups ' plasma , et-1 and tgf- 
 concentrations were statistically different .
the highest value 
 was obtained in the newborns with mas and the others were ordered 
 as rds , rds-2 , and the healthy newborns .
kaapa et al   in a similar study found that plasma et-1 concentrations were not correlated with the pulmonary pressure 
 but that high plasma concentrations of et-1 reflected severe 
 pulmonary damage . in another study
, there was a significantly 
 higher et-1 concentration in newborns with pulmonary hypertension 
 than healthy newborns or newborns with rds .
in contrast of our study , kuo et al   determined the highest values of plasma et-1 concentrations in the first six hours of life in the 
 newborns diagnosed as rds , and the newborns diagnosed as mas had 
 a second highest values of et-1 concentrations .
like our study , 
 kojima et al   found out that plasma et-1 concentrations in newborns with rds were higher compared to the newborns with 
 rds-2 .
a study of benjamin et al   demonstrated that infants with and without rds had similar umbilical cord et-1 
 concentrations , whereas et-1 concentrations were higher in rds 
 than in control newborns 1840 hours after birth .
the increased 
 vascular resistance in rds may be related to high plasma et-1 
 concentrations . in an experimental model of rds in the newborn lamb
, the et-1 
 concentration was increased after induction of rds concomitant 
 with the development of pulmonary hypertension , from an early 
 time point onwards .
increased et-1 concentration during rds 
 appeared to be reached in the early phase of pulmonary 
 hypertension development . also increased circulating levels of 
 et-1 were correlated with the severity of pulmonary hypertension 
 .
whereas , tgf- is secreted from the alveolar macrophages in 
 the lungs , and in case of damage it is responsible to the 
 organization of the fibrosis growth , inflammatory response , and 
 the recovery of the tissue .
for this reason , the 
 tgf- studies were realized in the patients with 
 bronchopulmonary displasia , where fibrosis was dominated 
 [ 23 , 24 ] . in our study , according to the results of plasma 
 et-1 levels , the first highest levels of tgf- were in 
 newborns with mas and the second were in newborns with rds .
starting from the moment of the diagnosis , it was 
 observed that et-1 concentrations of the patients who received 
 surfactant and mechanic ventilator supply were decreased .
kuo 
 et al   and niu et al   emphasized those plasma 
 et-1 concentrations of the newborns with and without 
 bronchopulmonar dysplasia did not show any difference . the 
 endothelium modulates vascular tone by releasing 
 endothelium - derivated vasodilatators , including nitric oxide , 
 prostacyclin , bradykinin , and vasoconstrictors such as et-1 and 
 angiotensin ii , in response to a number of biochemical and 
 physical stimuli .
recent studies have suggested that an imbalance 
 between nitric oxide and et-1 may contribute to changes in 
 vascular tone observed in these diseases .
a number of 
 vasculopathies associated with an impaired bioavailability of 
 nitric oxide have been found to be linked to enhanced sythesis of 
 et-1 . in our study
, plasma et-1 concentrations might have a 
 best indicator of the prognosis in the first six hours of life , 
 but tgf- concentrations did not have the same effect . 
 because it was a significant difference between the survivors and 
 dead newborns , in whom et-1 concentrations were higher in the 
 first six hours of life .
these newborns presented severe damage in 
 the lungs , starting from the first hour .
we did not see any other 
 study emphasizing this subject in the literature . as a result
, it was decided that , in the 
 differentiating diagnosis of the rds , rds-2 , and mas , which are a 
 significant problem of premature and mature newborns , the 
 investigation of et-1 and tgf- concentrations is 
 meaningful , but that in wider groups , it is required to determine 
 the borderline values .
it was observed that the et-1 levels 
 investigated in the first six hours are more useful in determining 
 the prognosis , and the et-1 concentrations investigated in the 
 following days are more meaningful presenting clinical recovery . 
 in the determination of prognosis
, tgf- concentration 
 invesitigated in the first six hours does not seem meaningful . 

since the results are still contradictory , it was emphasized that 
 it is required to carry out new researches .
plasma et-1 concentrations of the healthy premature and 
 mature newborns were 0.79  0.44 and 0.77  0.56 pg / ml , 
 respectively .
also tgf- concentrations in this group were 0.17  0.37 
 and 0.25  0.41 pg / ml , respectively , and was not 
 significantly different ( p > .05 ) .
et-1 concentrations according to diagnosis in the sick 
 newborns at the sixth hour after birth were 3.37  1.59 pg / ml in rds , 
 1.60  0.66 pg / ml in rds-2 , 5.70  5.87 pg / ml in mas , and 
 0.78  0.50 pg / ml in healthy group .
only the concentrations of et-1 in rds and mas groups were significantly different ( p < .05 ) . also plasma 
 tgf- concentrations were 2.05  0.98 pg / ml in rds , 
 1.59  0.66 pg / ml in rds-2 , 3.75  1.94 pg / ml in 
 mas and 0.22  0.39 pg / ml in healthy group .
only the 
 difference in rds and mas group was significant 
 ( p < .05 ) .
changes of the plasma 
 et-1 ( pg / ml ) concentrations during the oxygen treatment days 
 in the different dignostic newborns tended to decrease .
the 
 plasma et-1 concentrations in the sixth hour of life were 
 decreased at third day as 2.801.49 pg / ml in rds , 
 1.28  0.84 pg / ml in rds-2 , and 3.69  2.13 pg / ml 
 in mas group .
et-1 concentrations in the newborns who died were 
					 4.44  1.26 pg / ml in rds and 11.60  8.97 pg / ml in mas groups 
 ( p < .05 ) and in those who survived were 2.42  1.19 pg / ml in rds and 3.41  1.31 pg / ml ( p <
et-1 concentrations in the newborns who died were 
 3.70  1.31 pg / ml in rds and 7.30  0.00 pg / ml in mas group 
 ( p < .05 ) and in those who survived were 2.04  1.20 pg / ml in rds and 2.77  0.73 pg / ml ( p < .05 ) at the third day of life .
et-1 concentrations in the newborns who died were 
 3.42  1.27 pg / ml in rds and 7.00  0.00 pg / ml in mas group 
 ( p < .05 ) and in those who survived were 1.82  1.15 pg / ml in rds and 1.60  0.00 pg / ml ( p < .05 ) at the seventh day of life .
et-1 concentrations in the newborns who died were 
 3.03  0.95 pg / ml and in those who survived were 1.60  1.35 pg / ml in 
 rds ( p < .05 ) at the 14th day of life .
 the purpose of this present study was to evaluate the serum levels of et-1 and tgf- in the newborns with respiratory distress . in this study , newborns with respiratory distress hospitalized into the newborn intensive care unit were included . 
 the highest values of et-1 and tgf- were obtained from newborns with diagnosis as meconium aspiration syndrome ( 5.70  5.87 pg / ml and 3.75  1.94 pg / ml , resp ) in the sample obtained in the first six hours after birth , and these are statistically different from control group ( p < .05 ) . 
 also , same results were obtained for newborns with respiratory distress syndrome ( 3.37  1.59 pg / ml and 2.05  0.98 pg / ml , resp ) . after oxygen treatment , et-1 values obtained in the first six hours of life were decreased regularly in the following days ( p < .05 ) . in the differentiating diagnosis of the respiratory distress of newborns , 
 the investigation of et-1 and tgf- levels is meaningful . 
 the et-1 levels investigated in the first six hours is more useful in determining the prognosis , and repeating et-1 levels in the following days is more meaningful to determine clinical response . 
INTRODUCTION
MATERIALS AND METHOD
RESULTS
DISCUSSION
Figures and Tables