A Study On Genetic Polymorphism Of The Surfactant Protein A In Neonatal Respiratory Distress Syndrome

PrefaceNeonatal respiratory distress syndrome ( RDS) with higher morbidity and mortality is one of acute and severe diseases during newborn infant and an important cause of chronic pulmonary disease. The main cause of RDS is adeficien-cy of pulmonary surfactant due to premature lung development in premature infant , which consists of phospholipids and specific proteins. Variation of gene in regulating the synthesis of human surfactant protein is a hereditary mechanism in RDS. In the present study, the premature infants in the Chinese population was our subjects. By using SSCP method for detecting genetic polymorphism of the surfactant protein A in premature infant with RDS, we try to determin the susceptible gene to RDS and study the mechanism of RDS on the genetic level. According to this, we will propose the medical strategies for provention and therapy in RDS.Materials and MethodsThe premature infants diagnosed clinically as RDS are received in. experimental group and the normal premature infants in control group. Whole - blood samples 2ml were collected into plastic EDTA tubes in 3 days after birth. Ge-nomic DNA was isolated from the whole - blood speciment by use of phenol/ Chloroform method and were stored at - 20℃ until next step. By index the Gen-Bank in National library of medicine, we designed the primer sequence of 6A~2, 6A~3,1A~0,1A~1 by use of Computer software of primer 5. 0 Version. Genomic DNA were amplified by the use of PCR, 2% Agarose gel Electrophoresis. Thenegative and positive result of genetic detection were recorded. Allele frequency comparison were performed with the use of -^ analysis between infants with RDS and control. The difference was thought as there was statistic significance in difference if P < 0.05. Otherwise,there was no statistic significance.ResultIn 28 control infants, the frequency of the SP - A! allele 6A2 N6A3were 21. 4% ^10. 7% respectively. The frequency of 6A was higher than that of 6A . The frequency of the SP - A2 allele 1 A0 ^1 A1 were 67.9% >,82. 1% respectively. The frequency of 1A was slightly higher than that of 1A .In 18 infants with RDS, the frequency of SP - A, allele 6A\6A3were 50% N 5.6% respectively. The SP - Aj allele6A was overrepresented in the infants with RDS, compared with that in controls (frequency 50% ,,21.4% respectively;P <0. 05). The SP - Aj allele 6A3 tended to be underrepresented in the infants with RDS, compared with that in controls (frequency 5.6%^10.7% respectively;P>0. 05). But there was no significant difference between the infants with RDS and control . The frequency of SP - A2 allele 1 A0was 72. 2% in the infants with RDS. There was no significant difference between the infants with RDS and control. ( frequency72.2% ^67.9% respectively;P >0.05);The frequency of SP - A2 allele 1 A1 was 66.7% in the infants with RDS. There was no significant difference between the infants with RDS and control (frequency 66. 7% ^82.1% respectively;P>0.05)In the infants born at gestation <32wk, there was no significant difference between the infants with RDS and controls in the SP - Aj allele 6A\6A3 ,SP -A2 allele 1A°N1A1 distributions( P >0. 05). In the infants born at gestation > 32wk, the SP - Aj allele 6A was overrepresented in the infants with RDS, compared with controls (frequency 56% ^15% respectively;P<0.05). There were no significant difference between the infants with RDS and control in the SP - Aj allele 6A3 ,SP - A2 allele 1 A0 .1 A1 distributions( P > 0. 05).The rate of male infants with RDS was 77. 8% and female was 22. 2%.The incidence of RDS is higher in males than in females. The frequency distribution of the SP - Aj allele 6A2 was 50% ^26.7% respectively in the malesinfants with RDS and controls. The allele 6A2 was overrepresented in the male infants with RDS, compared with controls. But there were no significant difference between the infants with RDS and control (P >0. 05). The frequency distribution of the SP - A, allele 6A\SP - A2 allele lA°>>lA1was similar in the male infants with RDS, compared with controls (P > 0.05 ).Conclusion1. In the normal premature infants,the frequency of the SP - Aj allele 6A\ 6 A were lower than 25% and the frequency of the SP — A2 allele 1 A0 ^1 A1 were higher than 65%. The overrepresentation of the SP - A2 allele lA^lA1 was a character in the premature infants of the present study.2. The SP - Aj allele 6A can be viewed as susceptible gene for RDS. Under the cooperate with premature, allele 6 A2 can make the infant more susceptible to RDS . When the infants were born at gestation > 32wk, allele 6A have a role as susceptible factors for RDS independently.