White C R, Hao X, Pearce W J
Center for Perinatal Biology, Department of Biochemistry, Loma Linda University School of Medicine, California 92350, USA.
Pediatr Res. 2000 Mar;47(3):369-75. doi: 10.1203/00006450-200003000-00014.
Basal cGMP concentrations are greater in immature than in mature cranial arteries, which may help explain why cerebrovascular resistance is lower in neonates than in adults. The present studies explore the hypothesis that this difference derives from age-related differences in soluble guanylate cyclase (sGC) activity. Maturation depressed (p < 0.01) maximal sGC activity (pmol cGMP/mg/min) in both carotid (from 11.10 +/- 0.50 to 3.60 +/- 0.20) and cerebral (from 3.10 +/- 0.31 to 1.45 +/- 0.08) arteries. Western blot analysis of relative sGC abundance (relative to sGC expression in adult kidney) found that sGC abundance was significantly greater (p < 0.05) in newborn carotid (0.38 +/- 0.04) and cerebral arteries (0.37 +/- 0.06) than in adult arteries (0.25 +/- 0.05 and 0.17 +/- 0.03, respectively). Basal Km values in carotid and cerebral arteries did not differ significantly between newborns (3- to 7-d old) and adults. Activation of sGC with nitrosylated heme significantly reduced Km values 3- to 5-fold in both types of artery and in both age groups. Within artery type, maturation had no significant effect on activated Km. Between artery types, activated Km values were greater (p < 0.05) in cerebral (200 +/- 40 microM) than in carotid (80 +/- 10 microM) arteries. Together, these data suggest that variations in sGC substrate affinity contribute to observed differences in sGC activity between artery types but not those between age groups. In contrast, variations in enzyme abundance, and possibly also enzyme-specific activity, appear responsible for differences in sGC activity associated with both age and artery type.
未成熟颅动脉中的基础环磷酸鸟苷（cGMP）浓度高于成熟颅动脉，这或许有助于解释为何新生儿的脑血管阻力低于成年人。本研究探讨了一种假说，即这种差异源于可溶性鸟苷酸环化酶（sGC）活性与年龄相关的差异。成熟过程使颈动脉（从11.10±0.50降至3.60±0.20）和脑动脉（从3.10±0.31降至1.45±0.08）中的最大sGC活性（pmol cGMP/mg/分钟）降低（p<0.01）。对相对sGC丰度（相对于成年肾脏中的sGC表达）进行的蛋白质印迹分析发现，新生颈动脉（0.38±0.04）和脑动脉（0.37±0.06）中的sGC丰度显著高于成年动脉（分别为0.25±0.05和0.17±0.03，p<0.05）。新生儿（3至7日龄）和成年人的颈动脉和脑动脉中的基础米氏常数（Km）值无显著差异。用亚硝基化血红素激活sGC可使两种动脉类型和两个年龄组中的Km值显著降低3至5倍。在动脉类型内部，成熟对激活的Km无显著影响。在不同动脉类型之间，脑动脉（200±40微摩尔）中的激活Km值高于颈动脉（80±10微摩尔）（p<0.05）。总之，这些数据表明，sGC底物亲和力的变化导致了不同动脉类型之间sGC活性的差异，但与年龄组之间的差异无关。相比之下，酶丰度的变化以及可能的酶特异性活性似乎是与年龄和动脉类型相关的sGC活性差异的原因。
