Effects Of Maternal Water Deprivation During Late Gestation On Fetal And Offspring RAS

Background: Women may face mild to severe dehydration due to exercise, fever, hemorrhage, vomiting, and diarrhea during pregnancy. Water deprivation (WD) is a potent stimulation to affect body fluid balance, and can lead to both extracellular and intracellular dehydration. Renin-angiotensin system (RAS), as an endocrine system, plays a role in regulating body fluid balance, cardiovascular system, neuroendocrine activity, and water and salt intake. A lot of evidence suggests that WD could induce changes in body fluid balance and RAS components in adults. However, it is largely unknown of effects of WD during pregnancy on the development of fetal RAS, and of the heart and kidney.Barker theory hypothesizes diseases in fetal origins. There is now a body of substantial epidemiological and experimental evidence showing that intrauterine stress may program cardiovascular diseases such as hypertension in late life. Previous studies suggested that the RAS may play a critical role in pathophysiological progress of hypertension induced by adverse environment during fetal development. It is unknown whether exposure to prenatal WD can affect the RAS in its regulation of body fluid balance and cardiovascular system in the offspring. Hence, this project studies the effect of maternal WD during late term on the development of RAS, heart, kidney in both fetuses and offspring.PART 1 Effects of maternal WD during late gestation on development of fetus and fetal RASObjective: To determine the development of the RAS, heart and kidney of the fetus exposure to WD at late term.Methods: After three days of maternal WD, fetal body, heart, and kidney were weighted, and fetal blood gases and electrolytes were determined with a Nova analyzer, plasma osmolality was determined with an advanced digmatic osmometer. Both fetal and maternal plasma angiotensin (Ang)Ⅰ, AngⅡ, vasopressin (VP) and aldosterone (ALD) concentrations were measured by radioimmunoassay. The ultrastructures of fetal heart and kidney were detected by a transmission electron microscope and the renal blood flow was detected by a Laser Doppler. Protein and mRNA of AngⅡreceptors (ATR) in the fetal heart and kidney were determined with western-blot or real-time PCR, and ATG mRNA in the fetal liver was also determined.Results: Prenatal exposure to WD at late term significantly decreased weight of the fetal body, heart and kidney, and increased fetal plasma Na+, hematocrit and osmolality. Fetal liver ATG mRNA, plasma AngⅠ, AngⅡ, VP, and ALD concentrations were also increased following WD. Maternal WD during late gestation changed the ultrastructures in the fetal heart and kidney, and altered the expression of both protein and mRNA of ATR in the fetal kidney and heart. Fetal renal blood flow was reduced.Conclusion: Three days of maternal WD during late gestation significantly changed the concentrations of fetal RAS components, and affected the development of fetal heart and kidney.PART 2 Imprinting effect and function of RAS of adult offspring exposure to maternal WD during late gestationObjective: To determine the effect of maternal WD during late gestation on the RAS and its roles in regulation of body fluids and cardiovascular system in offspring. Methods: The offspring in both the control and WD groups were used. The adult offspring body, heart, and kidney were weighted. Blood gases and electrolytes were determined with a Nova analyzer, plasma osmolality was determined with an advanced digmatic osmometer, plasma AngⅠ, AngⅡ, VP, and ALD concentrations were measured by radioimmunoassay. Cardiovascular responses to intravenous injection of PD, losartan, and AngⅡ, and contractility of the thoracic aorta and mesenteric artery were determined. Protein and mRNA of ATR were measured with western blot and real-time PCR in both the heart and kidney of offspring, and ATG mRNA in fetal liver was also determined. The effect of WD on the RAS, body fluid balance, cardiovascular system, and both salt and water intake, offspring was determined.Results: Maternal WD during late gestation did not change the weights of body, heart and kidney, the blood gases and electrolytes, the concentrations of plasma AngⅠ, AngⅡ, VP and ALD in adult offspring, but maternal WD during late gestation significantly changed the ATG mRNA levels in liver, and both ATR mRNA and proteins in both heart and kidney in adult offspring. Cardiovascular responses to injection of PD, losartan and AngⅡwere notably enhanced in male not female adult offspring in WD group compared to control, but baroreflex sensitivity was notably attenuated in both male and female offspring. Compared to control, the ability of both thoracic aorta and mesenteric artery to vasoconstriction to AngⅡwas enhanced in adult offspring of WD group. After 48h of WD again, blood gases and electrolytes had no difference in adult offsprings between control and WD group, but the concentrations of plasma AngⅡ, VP and ALD, salt intake and blood pressure were significantly elevated in adult offsprings in WD group than those of control.Conclusion: Maternal WD during late gestation showed chronic influence on the RAS in the offspring. Cardiovascular responses to the stimulation following exposure to prenatal WD showed difference that was gender-dependent. The decrease of baroreflex sensitivity may be the mechanism for changes in the cardiovascular responses. Blood pressure and vasoconstriction to AngⅡwere significantly increased in the adult offspring exposure to prenatal WD. Response to stimulation, plasma AngⅡ, VP, and ALD concentrations were higher in the offspring exposure to prenatal WD than in the control, associated with an increase of salt intake. The data indicate an increase of risks for cardiovascular diseases such as hypertension in the adult offspring exposed to maternal WD during late gestation.PART 3 Effects of maternal WD during late gestation on expression of proteome in the heart and kidney of the offspringObjective: To determine the expression of proteome in both the heart and kidney in the adult male offspring exposure to maternal WD during late gestation. Methods: Two dimensional electrophoresis (2-DE) was used to detect differences of proteome expression between the control and WD group in the heart and kidney of the adult male offspring.Results: The basic distributions of total proteins were similar in both the heart and kidney in offsprings between the control and WD groups. The numbers of total proteins were 603±25 and 577±32 in the heart between the control and WD groups, in which thirty-three differential protein spots were identified. Total proteins were 975±30 and 1107±42 in the kidney between the control and WD groups, in which thirty-eight differential protein spots were identified.Conclusion: 2-DE profiles with high resolution and reproducibility of total proteins were established in both the heart and kidney between the control and WD groups, and the expressions of differential proteins were found.