The Study About The Effects And Mechanism On Lung Development Of Marginal Vitamin A Deficiency Beginning From Embronic Period In Young Rats

PartⅠEffects of marginal vitamin A deficiency beginning from embryonic period and vitamin A intervention on lung structure and epithelium in young ratsOBJECTIVE: To study if the lung structure and epithelium of young rats especially on postnatal stages will be impaired which are in marginal vitamin A deficiency beginning from embryonic period, and if there will be difference on the recovery after vitamin A intervention at the early age after birth.METHODS: Eighteen female rats were divided into control,marginal vitamin A deficiency(MVAD) and vitamin A intervention (VAI) groups in this study. In control group the dams and pups were fed with normal diet(VA 6500 IU/kg). In MVAD group the dams and pups were fed with MVAD diet(VA 400 IU/kg). In VAI group the mothers received MVAD diet till post partum, and then received normal diet. The offspring were given low-dose vitamin A from postnatal day 1 to day 7 and received normal diet after weaning. All the pups were respectively killed at day 1, 2 weeks and 8 weeks. We recorded the body and lung weight of all pups and detected the serum and lung tissue vitamin A concentration by HPLC. We monitored lung development, structure by morphometric analysis and RT-PCR for SP-B and SP-C mRNA level.RESULTS:①The marginal vitamin A deficient dams'and pups'serum vitamin A concentration lowed down and they always had not the manifestation of vitamin A deficiency. The lung tissue vitamin A concentration of MVAD group was lower than control group at 2 weeks and 8 weeks(P<0.05).VAI group serum and lung tissue vitamin A concentration recoveried to normal level at 2 weeks.②The body and lung weight of marginal vitamin A deficiency young rats were lower than the control rats at day 1 and 2 weeks. But body weight at 8 weeks had no difference in three groups. The relative lung weight has no difference in three groups.③morphometric analysis showed that MVAD resulted in changes of lung structure such as reduced numbers of alveoli (P<0.05) and total alveolar surface area (P<0.05), in addition to increased alveoli septa thickness (P<0.05) compared to the control group. In VAI group, total alveolar surface area didn't completely resume to normal level at 8 weeks, but other aspects were obviously improved.④The level of SP-B, SP-C mRNA significant increased in MVAD and VAI group at day 1, 2 weeks and 8 weeks(P<0.05).CONCLUSIONS:①marginal vitamin A deficiency beginning from embryonic period may impair the lung development and structure in young rats.②Most aspects were obviously improved if the vitamin A intervention performed at postnatal day 1 except that total alveolar surface area didn't completely resume to normal level at age 8 weeks.③Marginal vitamin A deficiency may also influenced the SP-B, SP-C mRNA level and could not recover by vitamin A intervention at early age after birth.PartⅡEffects of marginal vitamin A deficiency beginning from embryonic period on lung etracellular matrix in young ratsOBJECTIVE: To study if the lung etracellular matrix of young rats especially on postnatal stages will be impaired which are in marginal vitamin A deficiency beginning from embryonic period, and if there will be difference on the recovery after vitamin A intervention at the early age after birth.METHODS: Eighteen female rats were divided into control,marginal vitamin A deficiency(MVAD) and vitamin A intervention (VAI) groups in this study. The method of animal model was same with part I.All the pups were respectively killed at day 1, 2 weeks and 8 weeks. We used aldehyde-fuchsin for elastin fibers and Masson trichrome staining for collagen and chemical methods to measure the content of hydroxyproline.RESULTS:①In control group elastin fibers show normal, continuous form and which forms a continuous network in the alveolus, small and larger airways. But in the MVAD group the elastin fibers themselves show a coarser, discontinuous appearance and decrease at age 2 weeks and 8 weeks(P<0.05). In the VAI group increased elastin fiber deposits were detected at age 2 weeks and 8 weeks with a normal, organized manner②Exposure to MVAD resulted in reduced collagen deposits (P<0.05) at postnatal day 1, but increased deposits at age 2 weeks (P<0.05) and 8 weeks (P<0.05) in an unorganized manner. In the VAI group decreased collagen deposits were detected at age 2 weeks and 8 weeks with a normal, organized manner.③In MVAD group the content of hydroxyproline increased compared with control group at the same age (P<0.05). In VAI group the content of hydroxyproline recoveried to normal level at 2 weeks and 8 weeks.CONCLUSIONS:①marginal vitamin A deficiency beginning from embryonic period may decreased the elastic fiber and impaired the structure of elastic fiber.②marginal vitamin A deficiency beginning from embryonic period may also resulted the increased deposition of collagen and the structure turbulence at 2 and 8 weeks.③The impaired elastic fiber and collagen would recover completely by vitamin A intervention at early age after birth.Part III The mechanism of the effects of marginal vitamin A deficiency beginning from embryonic period on lung development in young ratsOBJECTIVE: To study the mechanism of the effects that marginal vitamin A deficiency beginning from embryonic period on the lung development in young rats.METHODS: Eighteen female rats were divided into control,marginal vitamin A deficiency(MVAD) and vitamin A intervention (VAI) groups in this study. The method of animal model was same with part I. All the pups were respectively killed at day 1, 2 weeks and 8 weeks. We detected the RARα, RARβ, RARγmRNA by half-quantified RT-PCR in lung. The relative intensity of fluorescence and distributing of RARα, RARβ, RARγin lung slices was measured by confocal laser scanning microscopy. And we detected the RARα, RARβ, RARγprotein level and subcellular localization by western-blotting. RESULTS:①The expression of RARs mRNA gradually decline from day 1 to 8 weeks. MVAD resulted the increased level of RARαand RARβ(P<0.05), have no difference on RARγ. VAI group can not resume to normal group.②The relative intensity of fluorescence (IF) of RARα, RARβ, RARγalso decline from day 1 to 8 weeks same with the mRNA level changes. MVAD resulted the increased IF of RARαand RARβsignificant increased (P<0.05) but have no difference on RARγ, except at 2 weeks. VAI group can not resume to normal group. The distributing of RARs had no difference in the three groups.③Western-blotting results showed that the protein level of RARs were same with RT-PCR and IF. There existed the transfer from nuclear to cytoplasm and effected by VA status.CONCLUSIONS:①The expression and subcellular localization of RARs have differences at different lung development period.②VA status would significant effect the expression and subcellular localization of RARs significant, MVAD would increase the RARs mRNA and protein level and transfer to nuclear. But VAI could not resume the change of RARs.