Effects Of Supplying Thyroid Hormones To Low-iodine Pregnant Rats Of Different Pregnancy On The Expression Of Growth-Associated Protein (GAP-43)and Synaptophysin (Syp) In The Brain Of Neonatal Rats

Objects:To study the effects of supplying thyroid hormones to low-iodine pregnant rats of different pregnancy on expression of GAP-43and SYP in the brain of neonatal rats, further found the possible mechanism behind supplying thyroid hormones to low-iodine pregnant rats to change the phenomenon of brain development lag caused by lack of thyroid hormone, then find a critical period and dose of treatment.Methods:There are160Wistar rats in one-month-old.male and female half.The female rats were randomly divided into eight groups.include:normal group and7low iodine groups.10rats per group.Rats were fed with low iodine feed.normal group were given200μg/L KIO3the total iodine intake is equivalent to rat physiological iodine requirements, other groups drunk deionized water.After3months.female rats were mated with normal mate rats.Rats of one low iodine group as Negative control are not supplied with thyroid hormone.The other six groups are differently supplied with high\medium\low doses of thyroid hormone in early pregnancy(pregnant1st-17th day) groups and late pregnancy (pregnant18th day-20th day after birth) groups.high\medium\low doses of thyroid hormone is respectively3.5\2\0.5μg/100g weight. Brain tissues of new-born,7-day-old.14-day-old.21-day-old,28-day-old in every group were taken out for samples.GAP-43,SYP mRNA expression was detected by real time PCR:The expression of GAP-43/SYP of every group was detected by Immunohistochemistry(SABC) method and image analysis method, and Western blot.results:In normal group GAP-43expression level gradually decreased with age (p<0.05), SYP expression level gradually increased with age (p<0.05) Low-iodine group were lower than the expression level of normal group during the same period (p<0.05). only in postneonatal28d group,GAP-43expression level is higher than the expression level of normal group during the same period (p<0.05) Expression level of treatment groups are higher than the expression level of Low-iodine group during the same period (p<0.05).Low iodine pregnant rats continue to be gived the middle-dose or high-dose of the thyroid hormone therapy from early to late pregnancy during the brain development, and offspring can reach the normal GAP-43and syp expression levels. Especially in the early pregnancyConclusion:thyroid hormones could upregulate the expression of GAP-43and syp in low-iodine pregnant rats in the brain of neonatal rats. And may promote synaptic enhancement and re-building, perfect the synaptic efficacy.