Wood Charles E, Chen Gin-Fu, Keller-Wood Maureen
Dept. of Physiology and Functional Genomics, University of Florida College of Medicine, P.O. Box 100274, Gainesville, FL 32610-0274, USA.
Am J Physiol Regul Integr Comp Physiol. 2005 Aug;289(2):R613-R619. doi: 10.1152/ajpregu.00722.2004.
Fetal baroreflex responsiveness increases in late gestation. An important modulator of baroreflex activity is the generation of nitric oxide in the brainstem nuclei that integrate afferent and efferent reflex activity. The present study was designed to test the hypothesis that nitric oxide synthase (NOS) isoforms are expressed in the fetal brainstem and that the expression of one or more of these enzymes is reduced in late gestation. Brainstem tissue was rapidly collected from fetal sheep of known gestational ages (80, 100, 120, 130, 145 days gestation and 1 day and 1 wk postnatal). Neuronal (nNOS), inducible (iNOS), and endothelial (eNOS) mRNA was measured using real-time PCR methodology specific for ovine NOS isoforms. The three enzymes were measured at the protein level using Western blot methodology. In tissue prepared for histology separately, the cellular pattern of immunostaining was identified in medullae from late-gestation fetal sheep. Fetal brainstem contained mRNA and protein of all three NOS isoforms, with nNOS the most abundant, followed by iNOS and eNOS, respectively. nNOS and iNOS mRNA abundances were highest at 80 days' gestation, with statistically significant decreases in abundance in more mature fetuses and postnatal animals. nNOS and eNOS protein abundance also decreased as a function of developmental age. nNOS and eNOS were expressed in neurons, iNOS was expressed in glia, and eNOS was expressed in vascular endothelial cells. We conclude that all three isoforms of NOS are constitutively expressed within the fetal brainstem, and the expression of all three forms is reduced with advancing gestation. We speculate that the reduced expression of NOS in this brain region plays a role in the increased fetal baroreflex activity in late gestation.
胎儿压力反射反应性在妊娠晚期增强。压力反射活动的一个重要调节因子是脑干核中一氧化氮的生成，这些脑干核整合传入和传出反射活动。本研究旨在验证以下假设：一氧化氮合酶（NOS）同工型在胎儿脑干中表达，并且在妊娠晚期其中一种或多种酶的表达会降低。从已知胎龄（妊娠80、100、120、130、145天以及出生后1天和1周）的胎羊中快速采集脑干组织。使用针对绵羊NOS同工型的实时PCR方法测量神经元型（nNOS）、诱导型（iNOS）和内皮型（eNOS）mRNA。使用蛋白质印迹法在蛋白质水平上检测这三种酶。在单独制备用于组织学检查的组织中，确定了妊娠晚期胎羊延髓的免疫染色细胞模式。胎儿脑干含有所有三种NOS同工型的mRNA和蛋白质，其中nNOS最为丰富，其次是iNOS和eNOS。nNOS和iNOS mRNA丰度在妊娠80天时最高，在更成熟的胎儿和出生后动物中丰度有统计学意义的下降。nNOS和eNOS蛋白质丰度也随着发育年龄而降低。nNOS和eNOS在神经元中表达，iNOS在神经胶质细胞中表达，eNOS在血管内皮细胞中表达。我们得出结论，NOS的所有三种同工型在胎儿脑干中组成性表达，并且随着妊娠进展，所有三种形式的表达均降低。我们推测该脑区中NOS表达的降低在妊娠晚期胎儿压力反射活动增强中起作用。
