Inositol 1,3,4,5-tetrakisphosphate and not phosphatidylinositol 3,4-bisphosphate is the probable precursor of inositol 1,3,4-trisphosphate in agonist-stimulated parotid gland.
When [3H]inositol-prelabelled rat parotid-gland slices were stimulated with carbachol, noradrenaline or Substance P, the major inositol trisphosphate produced with prolonged exposure to agonists was, in each case, inositol 1,3,4-trisphosphate. Much lower amounts of radioactivity were present in the inositol 1,4,5-trisphosphate fraction separated by anion-exchange h.p.l.c. Analysis of the inositol trisphosphate head group of phosphatidylinositol bisphosphate in [32P]Pi-labelled parotid glands showed the presence of phosphatidylinositol 4,5-bisphosphate, but no detectable phosphatidylinositol 3,4-bisphosphate. Carbachol-stimulated [3H]inositol-labelled parotid glands contained an inositol polyphosphate with the chromatographic properties and electrophoretic mobility of an inositol tetrakisphosphate, the probable structure of which was determined to be inositol 1,3,4,5-tetrakisphosphate. Since an enzyme in erythrocyte membranes is capable of degrading this tetrakisphosphate to inositol 1,3,4-trisphosphate, it is suggested to be the precursor of inositol 1,3,4-trisphosphate in parotid glands.
D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D010306:Parotid Gland / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D013373:Substance P / Q000494:pharmacology; D013403:Sugar Phosphates / Q000378:metabolism*
D007295:Inositol Phosphates; D013403:Sugar Phosphates; C081655:inositol-1,3,4,5-tetrakisphosphate; D013373:Substance P; D015544:Inositol 1,4,5-Trisphosphate; D002217:Carbachol; D009638:Norepinephrine