Prenatal alcohol exposure and the effects on the developing kidney and long-term adult health outcomes

2017-01-15T23:59:02Z (GMT) by Gray, Stephen Peter
It is well known that chronic fetal exposure to high levels of alcohol can result in developmental abnormalities. However, the effects of low concentrations or acute exposure to ethanol on fetal development have been less well studied, and this is particularly the case for the kidney. In recent years, a variety of environmental factors have been shown to result in a deficit in nephron endowment, and numerous studies have associated this nephron deficit with the development of adult hypertension and renal functional abnormalities. This thesis explores the effects of chronic and acute fetal ethanol exposure on kidney development in sheep and rat models. In vitro and in vivo studies were conducted. To investigate the effects of chronic prenatal ethanol exposure on kidney development, pregnant ewes (Merino Border-Leicester) were intravenously infused with ethanol 0.75g/kg body weight per day, infused over 1hr from day 95 of gestation until day 134 of gestation (gestation in sheep is approximately 147 days). The fetal kidneys were then taken for unbiased stereological determination of total nephron number and quantitative real-time PCR analysis of gene expression. Ethanol-exposed fetal sheep kidneys contained 11% fewer nephrons than saline-exposed kidneys, but were similar in weight. Analysis of renal expression of 14 genes failed to identify any differences between ethanol-exposed and saline-exposed fetuses. This study has been published (Gray, SP, Kenna, K, Bertram, JF, Hoy, WE, Yan, EB, Bocking, AD, Brien, JF, Walker, DW, Harding, R & Moritz, KM: Repeated ethanol exposure during late gestation decreases nephron endowment in fetal sheep. American Journal of Physiology - Regulatory Integrative and Comparative Physiology, 295: R568-R574, 2008). To investigate the effects of acute prenatal ethanol exposure on kidney development and the long-term consequences for cardiovascular and renal function, pregnant Sprague-Dawley rats were administered ethanol (1g/kg) by gavage at embryonic days 13.5 and 14.5. Nephron number was determined in offspring at postnatal day 30, and cardiovascular and renal function were analysed at 6 months of age. Ethanol-exposed male and female offspring were growth restricted in comparison to controls for the first 30 days of postnatal life, and at postnatal day 30 the kidneys contained approximately 20% fewer nephrons. At 6 months of age, ethanol-exposed male and female offspring had a 10mmHg elevation in mean arterial pressure without changes in heart rate. Male ethanol-exposed offspring had elevated glomerular filtration rate and renal blood flow, while female ethanol-exposed offspring had lower glomerular filtration rate and renal blood flow, with elevated renal vascular resistance. Rat metanephric organ culture was employed to investigate the direct effects of ethanol on kidney development. In addition, retinoic acid, a promoter of kidney development was added to culture to determine whether any ethanol-induced alterations to kidney development could be prevented by co-culture with retinoic acid. Embryonic day 14 kidneys were cultured with ethanol (0.2%) and/or retinoic acid (10nM & 20nM), and ureteric branching morphogenesis was quantified after 48 hours. Kidneys cultured in the presence of ethanol contained 20% fewer ureteric branch points and tips than control kidneys. The ureteric trees in kidneys co-cultured with ethanol and retinoic acid (10nM) were similar to control kidneys, demonstrating retinoic acid could prevent the adverse effects of ethanol. The results of the studies described in this thesis demonstrate that prenatal ethanol exposure in both the chronic and acute settings results in a permanent reduction in nephron number. Acute (2 days) prenatal ethanol exposure in rats resulted in elevated arterial pressure and sex-specific changes in renal function at 6 months. In vitro experiments demonstrated aberrant changes in ureteric branching following culture in the presence of ethanol, and these changes could be blocked by co-culture with retinoic acid. This suggests that the retinoic acid signalling pathway may, in part, contribute to the effects of ethanol on the developing kidney. The present findings of the adverse effects of low levels of alcohol exposure on kidney development suggest further studies in this area are warranted. Ultimately, information from studies such as these should be used to advise pregnant women, and women considering becoming pregnant.