Investigation of the chronic effects of NPY by subcutaneous implantation of 6-23 cells producing NPY in WAG rats

Objective: In this experiment, we studied the chronic effects of NPY, as there were no data on long-term effects of NPY in vivo. Methods: Complementary DNA encoding NPY was isolated, sequenced and cloned into the expression vector, pCEP4. The 6-23 clone 6 cell line was transfected with this clone. Two groups of 10 adult male WAG rats (180–250 g body weight) were injected with either untransfected 6-23 clone 6 or 6-23 clone 6 transfected with NPY cDNA [6-23 (NPY)]. After 8 weeks, the animals were killed, their plasma assayed for insulin. Pancreatic glucagon (PG), by RIA, and plasma glucose were measured. Results: The transfected cells were shown to be producing fully processed, bioactive NPY. The expression of NPY was also confirmed by Northern blot analysis. The animals injected with 6-23 (NPY) cells gained significantly more weight than the controls, (on day 54, 31.89 ± 3.56 vs. 24.1 ± 4.12 g, n = 10, P< 0.05). Plasma insulin and PG increased significantly in NPY animals compared to controls. The total RNA extracted from tumours was analysed by Northern blotting and showed NPY mRNA expression in NPY animals, but not in controls. Conclusion: The long-term effects of NPY was confirmed by injection of the cells producing this peptide.