Characterization of choline acetyltransferase-sustaining and survival-promoting activities for parasympathetic neurons in pig lung.

A total of 49 tissues from six animal species were screened for substances that would sustain choline acetyltransferase (ChAT) in parasympathetic ciliary neurons in culture. Among these, lungs from several species, particularly pig, contained relatively high concentrations of ChAT-sustaining activity. The bioassay used was one in which embryonic chicken ciliary ganglia were cultured as explants for 3 days with KCl and lung extract. KCl, in the presence of lung extract, sustained high concentrations of choline acetyltransferase activity, but did not maintain enzymatic activity in the absence of lung extract. These effects were dependent on the embryonic age of the ciliary ganglia. Lung extract and KCl would not maintain choline acetyltransferase activity in parasympathetic neurons taken from chickens older than embryonic day 12. In addition to ChAT-sustaining activity, pig lung also contains survival-promoting activity for parasympathetic neurons but not for other neuronal types, including sympathetic or sensory neurons of neural crest or placodal origin. This is a more specific target spectrum than previously reported ciliary survival-promoting factors that have been purified or partially purified and indicates that survival-promoting activities in pig lung are different than those previously observed. Because of the large quantitites that can be obtained, we suggest that pig lung is a preparatively feasible source for possibly novel ciliary neuron ChAT-sustaining and survival-promoting activities for parasympathetic neurons.