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. 1983 Nov 15;216(2):433–441. doi: 10.1042/bj2160433

Phosphatidylinositol hydrolysis in isolated guinea-pig islets of Langerhans.

M P Schrey, W Montague
PMCID: PMC1152521  PMID: 6362663

Abstract

Previous studies have reported an increased turnover of phospholipid in isolated islets of Langerhans in response to raised glucose concentrations. The present investigation was thus undertaken to determine the nature of any phospholipases that may be implicated in this phenomenon by employing various radiolabelled exogenous phospholipids. Hydrolysis of 1-acyl-2-[14C]arachidonoylglycerophosphoinositol by a sonicated preparation of islets optimally released radiolabelled lysophosphatidylinositol, arachidonic acid and 1,2-diacylglycerol at pH 5,7 and 9 respectively. This indicates the presence of a phospholipase A1 and a phospholipase C. However, the lack of any labelled lysophosphatidylinositol production when 2-acyl-1-[14C]stearoylglycerophosphoinositol was hydrolysed argues against a role for phospholipase A2 in the release of arachidonic acid. Phospholipase C activity as measured by phosphatidyl-myo-[3H]inositol hydrolysis was optimal around pH8, required Ca2+ for activity and was predominantly cytosolic in origin. The time course of phosphatidylinositol hydrolysis at pH 6 indicated a precursor-product relationship for 1,2-diacylglycerol and arachidonic acid respectively. The release of these two products when phosphatidylinositol was hydrolysed by either islet or acinar tissue was similar. However, phospholipase A1 activity was 20-fold higher in acinar tissue. Substrate specificity studies with islet tissue revealed that arachidonic acid release from phosphatidylethanolamine and phosphatidylcholine was only 8% and 2.5% respectively of that from phosphatidylinositol. Diacylglycerol lipase was also demonstrated in islet tissue being predominantly membrane bound and stimulated by Ca2+. The availability of non-esterified arachidonic acid in islet cells could be regulated by changes in the activity of a phosphatidylinositol-specific phospholipase C acting in concert with a diacylglycerol lipase.

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Selected References

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  1. BLIGH E. G., DYER W. J. A rapid method of total lipid extraction and purification. Can J Biochem Physiol. 1959 Aug;37(8):911–917. doi: 10.1139/o59-099. [DOI] [PubMed] [Google Scholar]
  2. Bell R. L., Kennerly D. A., Stanford N., Majerus P. W. Diglyceride lipase: a pathway for arachidonate release from human platelets. Proc Natl Acad Sci U S A. 1979 Jul;76(7):3238–3241. doi: 10.1073/pnas.76.7.3238. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Clements R. S., Jr, Rhoten W. B. Phosphoinositide metabolism and insulin secretion from isolated rat pancreatic islets. J Clin Invest. 1976 Mar;57(3):684–691. doi: 10.1172/JCI108325. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Di Renzo G. C., Johnston J. M., Okazaki T., Okita J. R., MacDonald P. C., Bleasdale J. E. Phosphatidylinositol-specific phospholipase C in fetal membranes and uterine decidua. J Clin Invest. 1981 Mar;67(3):847–856. doi: 10.1172/JCI110102. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Freinkel N., El Younsi C., Dawson M. C. Inter-relations between the phospholipids of rat pancreatic islets during glucose stimulation, and their response to medium inositol and tetracaine. Eur J Biochem. 1975 Nov 1;59(1):245–252. doi: 10.1111/j.1432-1033.1975.tb02448.x. [DOI] [PubMed] [Google Scholar]
  6. Hirasawa K., Irvine R. F., Dawson R. M. Proteolytic activation can produce a phosphatidylinositol phosphodiesterase highly sensitive to Ca2+. Biochem J. 1982 Sep 15;206(3):675–678. doi: 10.1042/bj2060675. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Hirasawa K., Irvine R. F., Dawson R. M. The catabolism of phosphatidylinisitol by an EDTA-insensitive phospholipase A1 and calcium-dependent phosphatidylinositol phosphodiesterase in rat brain. Eur J Biochem. 1981 Nov;120(1):53–58. doi: 10.1111/j.1432-1033.1981.tb05669.x. [DOI] [PubMed] [Google Scholar]
  8. Irvine R. F. How is the level of free arachidonic acid controlled in mammalian cells? Biochem J. 1982 Apr 15;204(1):3–16. doi: 10.1042/bj2040003. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Lacy P. E., Kostianovsky M. Method for the isolation of intact islets of Langerhans from the rat pancreas. Diabetes. 1967 Jan;16(1):35–39. doi: 10.2337/diab.16.1.35. [DOI] [PubMed] [Google Scholar]
  10. Laychock S. G. Phospholipase A2 activity in pancreatic islets is calcium-dependent and stimulated by glucose. Cell Calcium. 1982 Mar;3(1):43–54. doi: 10.1016/0143-4160(82)90036-7. [DOI] [PubMed] [Google Scholar]
  11. Metz S. A., Fujimoto W. Y., Robertson R. P. Lipoxygenation of arachidonic acid: a pivotal step in stimulus-secretion coupling in the pancreatic beta cell. Endocrinology. 1982 Dec;111(6):2141–2143. doi: 10.1210/endo-111-6-2141. [DOI] [PubMed] [Google Scholar]
  12. Montague W., Parkin E. N. Changes in membrane lipids of the beta-cell during insulin secretion. Horm Metab Res Suppl. 1980;Suppl 10:153–157. [PubMed] [Google Scholar]
  13. Rittenhouse-Simmons S. Production of diglyceride from phosphatidylinositol in activated human platelets. J Clin Invest. 1979 Apr;63(4):580–587. doi: 10.1172/JCI109339. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Sagawa N., Okazaki T., MacDonald P. C., Johnston J. M. Regulation of diacylglycerol metabolism and arachidonic acid release in human amnionic tissue. J Biol Chem. 1982 Jul 25;257(14):8158–8162. [PubMed] [Google Scholar]
  15. Schrey M. P., Rubin R. P. Characterization of a calcium-mediated activation of arachidonic acid turnover in adrenal phospholipids by corticotropin. J Biol Chem. 1979 Nov 25;254(22):11234–11241. [PubMed] [Google Scholar]
  16. Shukla S. D. Minireview. Phosphatidylinositol specific phospholipases C. Life Sci. 1982 Apr 19;30(16):1323–1335. doi: 10.1016/0024-3205(82)90016-9. [DOI] [PubMed] [Google Scholar]
  17. Tanigawa K., Kuzuya H., Imura H., Taniguchi H., Baba S., Takai Y., Nishizuka Y. Calcium-activated, phospholipid-dependent protein kinase in rat pancreas islets of langerhans. Its possible role in glucose-induced insulin release. FEBS Lett. 1982 Feb 22;138(2):183–186. doi: 10.1016/0014-5793(82)80436-5. [DOI] [PubMed] [Google Scholar]
  18. Wassef M. K., Horowitz M. I. Degradation of phosphatidylinositol by soluble enzymes of rat gastric mucosa. Biochim Biophys Acta. 1981 Aug 24;665(2):234–243. doi: 10.1016/0005-2760(81)90007-2. [DOI] [PubMed] [Google Scholar]
  19. White D. A., Pounder D. J., Hawthorne J. N. Phospholipase A 1 activity of guinea pig pancreas. Biochim Biophys Acta. 1971 Jul 21;242(1):99–107. doi: 10.1016/0005-2744(71)90091-x. [DOI] [PubMed] [Google Scholar]
  20. Wightman P. D., Dahlgren M. E., Hall J. C., Davies P., Bonney R. J. Identification and characterization of a phospholipase C activity in resident mouse peritoneal macrophages. Inhibition of the enzyme by phenothiazines. Biochem J. 1981 Aug 1;197(2):523–526. doi: 10.1042/bj1970523. [DOI] [PMC free article] [PubMed] [Google Scholar]

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