Krewson et al. (1995) presented the steady-state data in the table below for the distribution of NGF in the vicinity of a thin cylindrical controlled drug release device implanted into the brain of a...

Krewson et al. (1995) presented the steady-state data in the table below for the distribution of NGF in the vicinity of a thin cylindrical controlled drug release device implanted into the brain of a rat. The polymeric disks containing radiolabeled I125-NGF were 2 mm in diameter and 0.8 mm in thickness. NGF has a molecular weight of 28,000 g mol−1. Assume that the NGF is eliminated from the brain tissue by a first order process, i.e., the rate of elimination is proportional to the concentration of NGF, i.e., kapparent CNGF where kapparent is the apparent first order elimination rate constant for NGF and accounts for processes such as metabolism, cellular internalization, or uptake by the brain’s systemic circulation. Then develop a steady-state reaction-diffusion model to analyze these data. The boundary conditions, assuming the origin of the Cartesian coordinate system to be the midline of the polymeric disk, are as follows:

is the value of kapparent? Using, Equation 8.30 calculate the half-life of NGF in the brain tissue.

How does this value of the NGF half-life compare to the reported half-life of NGF in brain tissue of about 1 h?

Equation 8.30