ObjectiveTo detect the development of retinal neovascularization (NV) induced by metabolic acidosis in neonatal rats and investigate the relationship between the occurrence of NV and vascular endothelial growth factor (VEGF). MethodsA total of 425 newborn Sprague-Dawley rats in experimental group underwent tubal feeding of NH4Cl (535 mg/kg) with the concentration of (50 mg/ml) (twice per day) from the 2nd day after the birth for 6 days and followed by a period of recovery. Additional 150 neonatal rats were in the control group without the tubal feeding. The rats were executed at the 3rd, 5th, 8th, 10th, 13th, 20th day after birth respectively. The retinal vessels were evaluated through retinal stretched preparation andadenosine diphosphatase (ADPase) staining; VEGF in retina was detected by enzymelinked immunosorbent assay(ELISA).ResultsIn the experimental group, the incidence of retinal NV at the 3rd, 5th, 8th, 10th, 13th, 20th day after birth was 0%，9%，26%，55%，19%, and 0% respectively. At the 3rd day, the expression of VEGF protein was lower in experimental group ［（101.1±14.2 ）pg/mg］ than that in the control group ［（133.2±15.9） pg/mg］（P＝0.004）, while at the 8th day it was higher in experimental group［(98.4±19.2) pg/mg］than that in the control group［（78.1±8.7） pg/mg］（P=0.028). There was no significant difference between the two groups at the 5th, 10th, 13th, and 20th day (Pgt;0.05). ConclusionsMetabolic acidosis may induce NV by injuring the developing retinal vessels. Retinal NV induced by acidosis relates to VEGF. (Chin J Ocul Fundus Dis, 2005,21:296-299)