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Induction of pancreatic duct cells of neonatal rats into insulin-producing cells with fetal bovine serum: a natural protocol and its use for patch clamp experiments.

AIM
To induce the pancreatic duct cells into endocrine cells with a new natural protocol for electrophysiological study.


METHODS
The pancreatic duct cells of neonatal rats were isolated, cultured and induced into endocrine cells with 15% fetal bovine serum for a period of 20 d. During this period, insulin secretion, MTT value, and morphological change of neonatal and adult pancreatic islet cells were comparatively investigated. Pancreatic beta-cells were identified by morphological and electrophysiological characteristics, while ATP sensitive potassium channels (K(ATP)), voltage-dependent potassium channels (K(V)), and voltage-dependent calcium channels (K(CA)) in beta-cells were identified by patch clamp technique.


RESULTS
After incubation with fetal bovine serum, the neonatal duct cells budded out, changed from duct-like cells into islet clusters. In the first 4 d, MTT value and insulin secretion increased slowly (MTT value from 0.024+/-0.003 to 0.028+/-0.003, insulin secretion from 2.6+/-0.6 to 3.1+/-0.8 mIU/L). Then MTT value and insulin secretion increased quickly from d 5 to d 10 (MTT value from 0.028+/-0.003 to 0.052+/-0.008, insulin secretion from 3.1+/-0.8 to 18.3+/-2.6 mIU/L), then reached high plateau (MTT value >0.052+/-0.008, insulin secretion >18.3+/-2.6 mIU/L). In contrast, for the isolated adult pancreatic islet cells, both insulin release and MTT value were stable in the first 4 d (MTT value from 0.029+/-0.01 to 0.031+/-0.011, insulin secretion from 13.9+/-3.1 to 14.3+/-3.3 mIU/L), but afterwards they reduced gradually (MTT value <0.031+/-0.011, insulin secretion <8.2+/-1.5 mIU/L), and the pancreatic islet cells became dispersed, broken or atrophied correspondingly. The differentiated neonatal cells were identified as pancreatic islet cells by dithizone staining method, and pancreatic beta-cells were further identified by both morphological features and electrophysiological characteristics, i.e. the existence of recording currents from K(ATP), K(V), and K(CA).


CONCLUSION
Islet cells differentiated from neonatal pancreatic duct cells with the new natural protocol are more advantageous in performing patch clamp study over the isolated adult pancreatic islet cells.