TABLE 1.

Differences in characteristics of VA kinetics between adult rats and neonatal rats¹

Characteristic	Adult rats	Control neonatal rats	VARA-supplemented neonatal rats
Recycling number2	∼12–13	144	100
Transit time in plasma,3 h	1.90	0.40	0.14
Plasma REs cleared by liver, %	∼75	52	22
Plasma REs cleared by intestine, %	NA	4.7	32
Plasma REs cleared by carcass, %	NA	40	43
Plasma retinol turnover to liver, %	48	76	56

¹Data for adult rats are from reference 22, and data for neonatal rats are from reference 41. NA, not available because of administration of retinol tracer directly into plasma (Figures 2A and 3A); RE, retinyl ester; VA, vitamin A; VARA, vitamin A and retinoic acid.

²Average number of times a retinol molecule recycles through plasma before it irreversibly exits it.

³Mean of the time that a retinol molecule spends in plasma during a single transit before leaving reversibly or irreversibly.