title: Effects of 3-isobutyl-1-methylxanthine on neonatal pancreatic islets maintained in tissue culture.
abstract: The phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) promoted the formation of monolayers in cultured pancreatic islets isolated from neonatal rats. Immunofluorescence with specific antisera to insulin and glucagon revealed B-cells and A-cells in these monolayers. Glucose-mediated insulin release was increased by raising the glucose concentration from 5 to 10 mmoles/l. Addition of IBMX (0.1 mmoles/l) to medium containing 10 moles/l glucose produced a further increase in insulin release. Recovery of total insulin, i.e. intracellular insulin plus insulin secreted, was also increased by approximately 50% after 8 days of culture. The B-cells showed a marked biosynthetic response to an acute glucose challenge after prior culture with 10 mmoles/l glucose. Although both unstimulated (1.5 mmoles/l glucose) and stimulated rates (1.5 mmoles/l glucose) of [3H]leucine incorporation into (pro)insulin were significantly higher following culture in 10 mmoles/l glucose plus IBMX (0.1 mmoles/l) than after prior culture with 10 mmoles/l glucose alone, the percentage of (pro)insulin synthesized in relation to total protein synthesis was only increased at the low concentration of glucose. These studies demonstrate that monolayer cultures of neonatal B-cells can be readily produced by IBMX and maintained in a functional state, as defined by their secretory and biosynthetic response. It is suggested that the phosphodiesterase inhibitor exerts a sensitizing effect on the responsiveness of the B-cell to glucose. Moreover, the culture system employed in the present study may prove to be useful for further studies of various agents affecting the B-cell function.
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology*; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D046508:Culture Techniques; D005455:Fluorescent Antibody Technique; D005947:Glucose / Q000494:pharmacology; D006651:Histocytochemistry; D007328:Insulin / Q000378:metabolism; D007515:Islets of Langerhans / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011384:Proinsulin / Q000096:biosynthesis; D051381:Rats; D011919:Rats, Inbred Strains; D013806:Theophylline / Q000031:analogs & derivatives*
chemical_list: D007328:Insulin; D011384:Proinsulin; D013806:Theophylline; D005947:Glucose; D015056:1-Methyl-3-isobutylxanthine