Figure 3.
Effect of cationic amino acids on cellular uptake and permeability of albuterol. (A) Two amino acids, lysine (lys) and histidine (His), known to be transported by cationic amino-acid transporters, were assessed for their ability to inhibit cellular albuterol uptake. Histidine and lysine demonstrated a potent inhibition of cellular uptake, suggesting that amino-acid transporters may be involved in the cellular uptake of albuterol. (B) Neither histidine nor lysine showed any significant inhibition of transepithelial albuterol flux (P > 0.05). All data represent the mean ± SE for n = 4 experiments from two different lungs. *P < 0.05. Papp, apparent permeability.