PERMEABILITY OF FERRET TRACHEA IN-VITRO TO TC-99M-DTPA AND [C-14] ANTIPYRINE

Platelet-activating factor (PAF) and vasoactive drugs were tested on permeability of ferret trachea in vitro by measuring fluxes of Tc-99m-diethylenetriamine pentaacetic acid (Tc-99m-DTPA; hydrophilic) and [C-14]antipyrine ([C-14]Ap; lipophilic) across the tracheal wall. Tracheae were bathed on both sides with Krebs-Henseleit buffer, with luminal buffer containing either Tc-99m-DTPA or [C-14]AP. Luminal and abluminal radioactivities, potential difference, and tracheal smooth muscle tone were measured. Baseline Tc-99m-DTPA and [C-14]AP permeability coefficients were -4.7 +/- 0.6 (SE) X 10(-7) and -2.2 +/- 0.1 X 10(-5) cm/s, respectively. PAF (10 mu M) increased permeability to Tc-99m-DTPA to -35.3 +/- 7.6 X 10(-7) cm/s (P < 0.05), but permeability to [C-14]AP did not change, suggesting that paracellular but not transcellular transport was affected. Abluminal and luminal applications of methacholine (MCh, 20 mu M), phenylephrine (PE, 100 mu M), and albuterol (Alb, 100 mu M) caused no change in permeability to Tc-99m-DTPA before or after exposure to luminal PAF, but abluminal histamine (Hist, 10 mu M) significantly increased permeability. Abluminal Hist decreased permeability to [C-14]AP before and after exposure to PAF. MCh, PE, and Hist increased smooth muscle tone; Alb and PAF had no effect. Thus, only PAF and Hist altered permeability to Tc-99m-DTPA, and MCh, PE, and Hist changed smooth muscle tone. Tracheal permeability changes were greater for the hydrophilic than for the lipophilic agent.