title: Opposing effects of glucose and tolbutamide on the sodium content of rat pancreatic islets.
abstract: Integrating flame photometry was employed for measuring sodium in rat pancreatic islets incubated in media buffered with HEPES or bicarbonate. The sodium content decreased by nearly 40% when the islets were exposed to 5 mmol/l glucose, no further reduction being seen with additional rise of the concentration to 20 mmol/l. Whereas the depressing effect of glucose was mimicked by 100 mumol/l quinine, increased sodium contents were noted after inhibition of the Na/K pump (removal of extracellular K+ or addition of 1 mmol/l ouabain) or exposure of the islets to 1 mmol/l tolbutamide. Although promoting sodium accumulation in the islet cells, tolbutamide counteracted the increase in sodium obtained on withdrawal of K+ from the incubation medium. It is suggested that tolbutamide in addition to its major effect in promoting the entry of Ca2+ also facilitates insulin release by suppressing the outward transport of this ion.
authors.affiliation: Department of Medical Cell Biology, University of Uppsala, Sweden.
authors.forename: L
authors.initials: L
authors.lastname: Ali
authors.forename: N
authors.initials: N
authors.lastname: Wesslén
authors.forename: B
authors.initials: B
authors.lastname: Hellman
mesh_terms: D000818:Animals; D005947:Glucose / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000032:analysis*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000032:analysis*; D014044:Tolbutamide / Q000494:pharmacology*
chemical_list: D014044:Tolbutamide; D012964:Sodium; D005947:Glucose