Uptake of 1:2-14C-choline by the guinea-pig lung in vitro: and the effects of p-terphenyl hemicholinium-3.

1. The perfused guinea-pig lung in vitro released a total of 290 +/- 24 nmol choline after 65 min. At the end of perfusion, there were 525 +/- 36 nmol choline and 11.6 +/- 0.5 mg lecithin per g of lung tissue. 2. When perfused with 1:2-(14) C-choline at 20 nmol (20 nCi)/ml for 70 min, the level of choline in the perfusion fluid remained at 20 nmol/ml; but 65% of radioactivity was abstracted by the lung. 21% of the sequestered radioactivity was in choline phospholipids, chiefly lecithin. 3. The p-terphenyl analogue of hemicholinium no. 3 (TPHC-3), when added into the perfusion fluid at concentration 30 nmol/ml, increased significantly both the 14C-choline uptake and the conversion of 14C-choline to 14C-lecithin in the lung. However, it did not change the total tissue concentration of choline and lecithin in the lung. 4. The lung seems to have separate uptake and release mechanisms for choline and these are in equilibrium. 5. The effects of TPHC-3 on the lung in this study may be secondary to its respiratory depressant action.