Production of inositol trisphosphates and inositol tetrakisphosphate in stimulated pancreatic islets.
Glucose and carbamylcholine caused concentration-dependent increases in the production of total [3H]inositol phosphates in [3H]inositol-labelled rat pancreatic islets. When extracts from islets stimulated with glucose, carbamylcholine or depolarising concentrations of K+ were analysed using anion-exchange high performance liquid chromatography, increased production of [3H]Ins1,4,5-P3 was detected, and in addition, elevated levels of two other labelled compounds which co-chromatographed with Ins1,3,4-P3 and Ins1,3,4,5-P4. In the case of carbamylcholine and high K+, such an effect was apparent within 20 s, whereas glucose appeared to cause a delayed response. In the presence of 5 mM LiCl, the accumulation of Ins1,3,4-P3 was more marked. The presence of LiCl had no major influence on the levels of Ins1,4,5-P3 or Ins1,3,4,5-P4. It is suggested that the stimulation of pancreatic islets with glucose, carbamylcholine or high K+ results in the hydrolysis of inositol lipids with the production of Ins1,4,5-P3 and in addition, Ins1,3,4-P3 and Ins1,3,4,5-P4. The physiological functions of these novel inositol phosphates in islets remain to be established.
D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002712:Chlorides / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D005947:Glucose / Q000494:pharmacology; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000096:biosynthesis*; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008094:Lithium / Q000494:pharmacology; D018021:Lithium Chloride; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D013403:Sugar Phosphates / Q000096:biosynthesis*
D002712:Chlorides; D007295:Inositol Phosphates; D013403:Sugar Phosphates; D015544:Inositol 1,4,5-Trisphosphate; D002217:Carbachol; D008094:Lithium; D018021:Lithium Chloride; D005947:Glucose; D011188:Potassium