Effects And Its Underlying Mechanisms Of High-Sucrose Diet During Pregnancy On Vascular Tension Of Thoracic Aorta In Fetal Rats

Objective: To investigate the effects and its underlying mechanisms of high-sucrose diets during pregnancy on vascular tension of thoracic aorta in fetal rats.Methods: Three-month-old Specific Pathogen Free（SPF）grade male and female SD rats are bred 1:2.The next morning found vaginal suppository as pregnancy,and considered as the first day of gestation.Pregnant rats were randomly divided into control（CON: purified water and standard food,N=20）and high-sucrose group（HS:20% sucrose solution,N=20）through pregnancy.At day 21 of pregnancy,infants were taken after aesthesia by using sodium pentobarbital（50mg/kg）.The pregnant rats and infants were weighed separately.The thoracic aorta was isolated microscopically and stained with HE to observe the differences in vascular structure.The DMT vascular tension detector was used to measure the tension of the thoracic aorta in both groups,while the expression of related molecules was also measured using real-time quantitative PCR and Western blot.Results:（1）Compared to CON,the body weight of pregnant rats and fetal rats was significantly higher in HS（P < 0.05）;there was no significant difference in the number of fetal rats per litter between the CON and HS groups.（2）Histological analysis of HE-stained sections showed that the vessel walls were thicker in the HS group compared to CON.（3）AII induced vasoconstriction was significantly higher in the HS group than in the CON group.（4）The vasoconstriction response of the two groups was examined by incubating the inhibitor of AT1 R,Losartan,and the inhibitor of AT2 R,PD123319,respectively.Consistent with the functional results,the protein expression of AT1 R was significantly higher in the HS group.（5）After incubation with L-name（L-name,e NOS inhibitor）,an inhibitor of e NOS synthase,there was no significant change in AII-induced contraction in either group,suggesting that the diastolic function of the endothelium contributes only marginally to the difference in vascular tone.（6）The function of the L-type calcium channel,the main calcium channel in the cell membrane,was first assayed,and Nifedipine a specific inhibitor of the L-type calcium channel,was incubated in isolated thoracic aortic vascular rings,and the AII-induced vasoconstriction was found to be significantly reduced in both groups,demonstrating that the L-type calcium channel plays a key role in AII-induced vasoconstriction;however,the magnitude of the reduction was significantly higher in the HS group than in the CON group,suggesting that the L-type calcium channel plays a key role in AII-induced vasoconstriction.The magnitude of the decrease in the HS group was significantly higher than that of the CON group,suggesting that the function of L-type calcium channels in the thoracic aorta of fetal rats was enhanced in the HS group,speculating may mediate an increase in the inward flow of extracellular calcium.（7）Further detection of calcium release from the SR in cells incubated with specific inhibitors of Inositol 1,4,5-trisphosphate receptors in isolated vascular rings of the thoracic aorta 2-APB,all AII-induced vasoconstriction was found to be significantly reduced,demonstrating that IP3 R also has a role in AII-induced vasoconstriction;however,the magnitude of reduction was also higher in the HS group than in the CON group,indicating that the function of IP3 R in the SR of the thoracic aorta of fetal rats in the HS group was enhanced.However,the magnitude of the decrease was also higher in the HS group than in the CON group,indicating that the function of IP3 R was enhanced in the SR of fetal rat thoracic aorta in the HS group;while incubation with Ryanodine,an inhibitor of ryanodine receptors,before and after incubation,revealed no significant change in vascular tone in the CON and HS groups,indicating that RyRs had little role in AII-induced vasoconstriction in the fetal rat thoracic aorta.（8）Finally,detecting the function of BK,an important ion channel in the cell membrane,was examined by incubating IBTX,an inhibitor of BK channels,and IBTX was found to significantly elevate AII-induced vasoconstriction in CON,but not in HS,indicating a significant downregulation of BK channel function in the HS thoracic aorta;and a significant decrease in molecular expression of BK channels in the HS thoracic aorta.Conclusion: The main findings of the study are as follows:（1）The high glucose diet during pregnancy increases AII-induced vasoconstrictor response in fetal rat thoracic aorta significantly,that mainly associated with enhanced AT1 R function,but not with AT2 R.（2）Endothelial diastolic function playes a minor role in the vasotonic response of the fetal aorta.（3）High-glucose diet during pregnancy significantly increases the function of L-type calcium channels and IP3 R in the SR.（4）High-glucose diet during pregnancy resultes in downregulation of BK channels in the thoracic aorta of fetal rats,which further causes an increase in intracellular calcium ions,thereby affecting vascular tone and ultimately increasing the risk of cardiovascular disease in the offspring of high glucose diet during pregnancy.