Inositol cycling and phosphoinositide metabolism in rat pancreatic islets.
The effects of extracellular inositol and LiCl on intra-islet inositol cycling were investigated in isolated rat islets. Islets were cultured for 7 days in inositol-free RPMI 1640 containing 11.1 mM glucose and labeled with 3.7 MBq myo-[2-3H] inositol for the final 3 days. The labeled islets were then perifused under various conditions. There was a persistent increase in [3H] efflux from labeled islets stimulated with 16.7 mM glucose for 60 min. Addition of 5 mM inositol resulted in marked release of [3H] from islets and a decrease in radioactive inositol-lipid. When islets were perifused with 5 mM LiCl, the glucose-induced efflux of [3H] was greatly inhibited. The inhibitory effect of LiCl on [3H] efflux was partially corrected by the addition of 5 mM inositol. A prominent effect of LiCl was an increase in inositol monophosphate, indicating increased phospholipase C activity. This was detected within 5 min after glucose stimulation. The present data suggest that there is always very active intra-islet inositol cycling and that glucose can augument inositol-lipid metabolism.
Tanigawa
K
K
Department of Medicine, Northwestern University Medical School, Chicago, Illinois 60611.
Lewis
N J
NJ
Freinkel
N
N
D000818:Animals; D002478:Cells, Cultured; D002712:Chlorides / Q000494:pharmacology; D004336:Drug Antagonism; D005947:Glucose / Q000494:pharmacology; D006868:Hydrolysis; D066298:In Vitro Techniques; D007294:Inositol / Q000378:metabolism*; D007295:Inositol Phosphates / Q000096:biosynthesis; D007515:Islets of Langerhans / Q000378:metabolism*; D008094:Lithium / Q000494:pharmacology; D018021:Lithium Chloride; D010716:Phosphatidylinositols / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D010738:Type C Phospholipases / Q000378:metabolism
D002712:Chlorides; D007295:Inositol Phosphates; D010716:Phosphatidylinositols; D007294:Inositol; C047872:inositol 2-monophosphate; D008094:Lithium; D010738:Type C Phospholipases; D018021:Lithium Chloride; D005947:Glucose