Table 2.

Dose-response parameters of the inhibition of GlySar (Uptake) by L-histidine (Inh) in different regions of adult brain from PepT2 null mice

Tissue	No Inh (µL/g)	Imax (µL/g)	IC50 (µM)	r2	Max Inh (%)
Cortex	100 ± 5	82 ± 6	0.76 ± 0.27	0.942	82
Cerebellum	85 ± 5	70 ± 6	0.80 ± 0.35	0.949	82
Hippocampus	89 ± 4	69 ± 4	1.25 ± 0.38	0.951	78

Data shown as mean ± SD (n=3 per tissue region). Dose-response parameters were derived from the equation:

$$\mathit{\text{Uptake}}=\mathit{\text{No Inh}}-\frac{I_{\mathit{\text{max}}}\times Inh}{{IC}_{50}+Inh}$$

where No Inh is the uptake of GlySar in the absence of L-histidine; I_max is the maximal inhibition of GlySar uptake by L-histidine; IC₅₀ is the concentration of L-histidine at which one-half the I_max is reached; and r² is the coefficient of determination. Max Inh (%) is calculated as: 100 × I_max divided by No Inh, and represents the maximal inhibition observed when the concentration of L-histidine >> IC₅₀ (expressed as percentile).