The development of a blood‐brain barrier mechanism in foetal sheep

作者：Chris Evans, James M. Reynolds, Margaret L. Reynolds, Norman Ruthven Saunders, M. B. Segal · 发表于：The Journal of Physiology · 年份：1974 · DOI：10.1113/jphysiol.1974.sp010530 · 被引用次数：160 · 研究领域：Heme Oxygenase-1 and Carbon Monoxide、Neonatal and fetal brain pathology、Neonatal Health and Biochemistry

1. The penetration of a metabolically inert, small molecular radius lipid insoluble substance ([(13)C] and [(4)H]sucrose), from blood into brain and c.s.f., has been studied in developing sheep from 50 days gestation (term, 150 days) through to the new-born stage. Around 50 days gestation sucrose accumulated rapidly into brain and c.s.f., and reached a steady-state level in brain of about 12% of the plasma level by 3 hr. By 60 days sucrose penetrated less freely into brain and c.s.f.; the brain steady-state level was 10% by 4(1/2) hr. A large decrease in sucrose penetration occurred by 70 days gestation, and by 123 days (just before the time when a foetal lamb becomes viable) both the rate of penetration and the brain steady-state level of sucrose were similar to those of the adult of other species.2. The rate of c.s.f. secretion at different ages has been estimated by dye dilution during ventriculo-cisternal perfusion. The turnover of c.s.f. in 60 day foetuses was high (1.36%/min.g wet weight brain). From 123 days gestation to the adult stage the turnover was much lower, 0.02%/min.g at 123 and 137 days gestation and 0.01%/min.g in the adult ewe.3. A simple new method for measuring c.s.f. volume is described. The volume at 51 days was estimated to be 0.14 ml., S.E. +/- 0.03, n = 4 (brain weight = 0.87 g +/- 0.11), at 59 days it was 0.45 ml., S.E. +/- 0.04, n = 6 (brain weight = 2.0 g +/- 0.1) and near term it was 7.28 ml S.E. +/- 1.29, n = 4 (brain weight 42.0 g +/- 0.5).4. T...