Effect of glucose concentrations on functional maturation of monolayer-cultured B cells from the rat pancreas

ABSTRACT The effect of two concentrations of glucose on the maturation of the response of B cells was studied in pancreatic monolayer cultures of the neonatal rat using a perifusion system. After exposure for the initial 3 days to a medium with 5·5 mmol glucose/l and 10 μmol iodoacetic acid/l (day 3), in order to delete fibroblasts selectively, monolayer cultures were kept for a total of 12 days in medium with either 5·5 or 16·7 mmol glucose/l alone. On day 3, B cells responded in a monophasic fashion, with no significant second phase, to acute challenge with 16·7 mmol glucose/1. At a concentration of 10 mmol/l, leucine and 2-ketoisocaproate both produced only minimal increases in the second phase of secretion above the basal level. In contrast, B cells on day 7 cultured in 5·5 mmol glucose/l showed a biphasic response to glucose, leucine and 2-ketoisocaproate. The magnitude in response to glucose was well preserved at day 15 of culture, whereas the stimulatory effects of leucine and 2-ketoisocaproate decreased to 24–57% of that of B cells on day 7. Moreover, B cells on day 7 cultured in 16·7 mmol glucose/l responded in a biphasic manner to glucose, the response being 65% of that of B cells in 5·5 mmol glucose/l. Additionally, the response to leucine and 2-ketoisocaproate still appeared to be monophasic. At day 15 of culture, however, the response of B cells in 16·7 mmol glucose/l to glucose was 105%, to leucine 245% and to 2-ketoisocaproate 127% of that of B cells in 5·5 mmol glucose/l. In conclusion, these results suggest that cultivation in medium with 5·5 mmol glucose/l could induce precocious development of an adult pattern of insulin secretion compared with that in 16·7 mmol glucose/l and, in addition, that the medium with 16·7 mmol glucose/l is superior for long-term culture to the medium with 5·5 mmol glucose/l. J. Endocr . (1988) 118, 303–310