Fox D A, Rubinstein S D
College of Optometry, University of Houston, TX 77204.
Exp Eye Res. 1989 Feb;48(2):237-49. doi: 10.1016/s0014-4835(89)80073-9.
Electroretinographic, morphometric and cyclic nucleotide metabolism studies in adult hooded rats have established that low-level lead exposure during early postnatal development (postnatal days 0-21) causes long-term selective rod deficits and degeneration. To determine if this same low-level lead exposure during early postnatal development produces immediate and/or long-term alterations in retinal sensitivity we examined ERG b-wave threshold responses in dark-adapted control and lead-exposed rats at 1-, 3- and 12 months of age. In addition, to determine possible sites and mechanisms of action responsible for the observed decreases in retinal sensitivity we analyzed the rhodopsin content per eye, the lambda max of rhodopsin and rod outer segment (ROS) length in superior and inferior posterior retina at 1-, 3- and 12 months of age. Relative to adult (3-month-old) controls whose log threshold was arbitrarily set at 0 log units, the mean log relative threshold in control rats was 0.4 log units at 1 month of age and 0.2 log units at 1 yr of age. In contrast, the mean log relative threshold in lead-exposed rats was 1.3 log units at 1 month of age and 1.1-1.2 log units at 3- and 12 months of age. Thus, compared with controls, retinal sensitivity in lead-exposed rats was decreased approx. 1 log unit at all ages examined. The rhodopsin content per eye in control rats increased 13% between 1- and 3 months of age, reaching an adult value of 1.99 nmol per eye, and then decreased 8% by 1 yr of age. In contrast, the eyes from lead-exposed rats contained 30-34% less rhodopsin at all ages examined. No change in the lambda max of rhodopsin was observed in the retinas from the lead-exposed rats. In both controls and lead-exposed rats, the developmental changes in log b-wave relative threshold were paralleled by linear increases and decreases in rhodopsin content per eye such that a log-linear relation between retinal sensitivity and rhodopsin content per eye existed between 1- and 12 months of age. The developmental changes in the superior and inferior retinal ROS length were similar in control and lead-exposed rats: ROSs were at their adult length at 1 month of age and then slightly decreased by 1 yr of age.(ABSTRACT TRUNCATED AT 250 WORDS)
对成年带帽大鼠进行的视网膜电图、形态学和环核苷酸代谢研究表明，出生后早期发育阶段（出生后0 - 21天）的低水平铅暴露会导致长期的选择性视杆细胞缺陷和退化。为了确定出生后早期发育阶段的这种低水平铅暴露是否会在视网膜敏感性方面产生即时和/或长期改变，我们检测了1、3和12月龄的暗适应对照大鼠和铅暴露大鼠的视网膜电图b波阈值反应。此外，为了确定导致观察到的视网膜敏感性降低的可能作用部位和机制，我们分析了1、3和12月龄大鼠上、下后视网膜每只眼睛的视紫红质含量、视紫红质的最大吸收波长以及视杆细胞外段（ROS）长度。相对于成年（3月龄）对照大鼠（其对数阈值被任意设定为0对数单位），对照大鼠在1月龄时的平均对数相对阈值为0.4对数单位，1岁时为0.2对数单位。相比之下，铅暴露大鼠在1月龄时的平均对数相对阈值为1.3对数单位，3月龄和12月龄时为1.1 - 1.2对数单位。因此，与对照相比，铅暴露大鼠在所有检测年龄的视网膜敏感性均降低了约1对数单位。对照大鼠每只眼睛的视紫红质含量在1至3月龄之间增加了13%，达到成年值每只眼睛1.99 nmol，然后到1岁时下降了8%。相比之下，在所有检测年龄，铅暴露大鼠眼睛中的视紫红质含量均减少30 - 34%。在铅暴露大鼠的视网膜中未观察到视紫红质最大吸收波长的变化。在对照大鼠和铅暴露大鼠中，对数b波相对阈值的发育变化与每只眼睛视紫红质含量的线性增减平行，使得在1至12月龄之间视网膜敏感性与每只眼睛视紫红质含量之间存在对数线性关系。对照大鼠和铅暴露大鼠上、下视网膜ROS长度的发育变化相似：ROS在1月龄时达到成年长度，然后到1岁时略有下降。（摘要截选至250字）
