These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Stimulation by prostaglandin E2 of a high-affinity GTPase in the secretory granules of normal rat and human pancreatic islets.
    Author: Kowluru A, Metz SA.
    Journal: Biochem J; 1994 Jan 15; 297 ( Pt 2)(Pt 2):399-406. PubMed ID: 7905262.
    Abstract:
    Recent reports of a pertussis-toxin (Ptx)-sensitive inhibition of glucose-induced insulin release by prostaglandin E2 (PGE2) in transformed beta-cells prompted us to look for the presence of prostaglandin-regulatable GTP-binding proteins (G-proteins) on the secretory granules of normal pancreatic islets. PGE2 (but not PGF2 alpha, PGA2, PGB2 or PGD2) stimulated in a concentration-dependent manner a high-affinity GTPase activity in the secretory-granule-enriched fractions of both normal rat and human islets. Similar results were found after sucrose-density-gradient-centrifugation-based isolation of secretory granules to those after a differential-centrifugation procedure. Half-maximal stimulation occurred at 800 nM PGE2, a concentration known to inhibit both phases of glucose-induced insulin secretion from pure beta-cell lines. The GTPase stimulatory effect of PGE2 was blocked virtually totally by Ptx pretreatment; it was not due to an effect on substrate binding since no measurable effect of PGE2 on binding of guanosine 5'-[gamma-[35S]thio]triphosphate was observed in cognate fractions. Other Ptx-sensitive inhibitors of insulin secretion (such as adrenaline or clonidine) also stimulated GTPase activity, suggesting that one (or more) inhibitory exocytotic G-proteins (i.e. a putative GEi) is located on the secretory granules. These studies demonstrate, for the first time in an endocrine gland, the presence of a regulatable G-protein, strategically located on the secretory granules where it might regulate the exocytotic cascade distal to both plasma-membrane events and the generation of soluble mediators of insulin secretion.
    [Abstract] [Full Text] [Related] [New Search]