Prenatal exposure to nicotine modifies kidney weight and blood pressure in genetically susceptible rats:: A case of gene-environment interaction

Background: Epidemiologic studies suggest that in utero exposure to maternal smoking is associated with elevated blood pressure (BP) later in life. Our aims were: (1 ) to examine effects of intrauterine exposure to nicotine on BP and hypertension target-organ size in rats; and (2 ) to investigate whether such effects depend on genetic background, by studying two genetically distinct strains of rats: the spontaneously hypertensive rat (SHR) and the normotensive Brown Norway (BN) rat. Methods. Nicotine or saline was administered to dams via subcutaneous osmotic minipumps throughout gestation. In nine-week-old male offspring, we measured BP and heart rate, assessed the weight of kidneys and heart, and determined fasting levels of glucose, insulin, triglycerides (TG), and cholesterol. We also measured gene expression of the insulin-like growth factor (IGF) system in the liver and kidneys. Results. SHR and BN offspring differed in their response to intrauterine exposure to nicotine. SHR exposed to nicotine (vs. saline) exhibited higher BP (P < 0.02) and serum cholesterol levels (P = 0.01), and lower kidney weight (P < 0.0001). In contrast, BN rats did not demonstrate differences between the nicotine and saline groups in these variables, but the nicotine-exposed BN rats showed a significant up-regulation in the gene expression of IGF-1 in the liver (P < 0.0001) and IGF receptor in the kidney (P = 0.006). Conclusion. These results suggest that intrauterine exposure to nicotine alters the cardiovascular system depending on the genetic background and, as such, supports the notion that the intrauterine environment interacts with genes in determining an individual's health later in life.