RETROVIRAL-MEDIATED GENE-TRANSFER OF THE PORCINE CHOLINE-ACETYLTRANSFERASE - A MODEL TO STUDY THE SYNTHESIS AND SECRETION OF ACETYLCHOLINE IN MAMMALIAN-CELLS

We have constructed a recombinant retrovirus that expresses choline ac etyltransferase (ChAT) by placing the porcine enzyme cDNA under the co ntrol of the 5' long terminal repeat of the retroviral vector pMMuLV. Using retrovirus-mediated gene transfer, we have expressed ChAT in ast roglial (STR-SVLT) and neuroendocrine (RIN) cell lines. Both genetical ly modified cell types synthesize acetylcholine (ACh). ACh is also pre sent in the culture medium at a low concentration relative to that fou nd in the modified cells. This result suggests that the synthesized AC h is retained within the cells and released by these two cell types. R elease of ACh is not increased in the presence of the calcium ionophor e A23187 or by depolarizing concentrations of potassium in either STR- SVLT or in RIN cells. The implications of these studies for understand ing ACh release mechanisms are discussed.