The influence of aging on whole body choline release and clearance

We have confirmed that hypoxia elicits a substantial rise in blood choline levels in young adult rats. An intravenous infusion of tracer quantities of [2H4]-Ch, serial measurements of blood [2H0]-Ch and [2H4]-Ch, and a simple pharmacokinetic model were used to assess the bidirectional flux of choline between the central pool and peripheral pools before, during and after a period of imposed hypoxia, in rats ranging from 56 to 780 days of age. The results indicate that the age-dependence of the hypercholinemic response to hypoxia is predominantly due to an increase in the amount of choline released in response to hypoxia, and that changes in its clearance are relatively unimportant.