title: Properties of receptor-controlled inositol trisphosphate formation in parotid acinar cells.
abstract: Activation of muscarinic receptors in rat parotid cells results in breakdown of polyphosphoinositides liberating inositol phosphates, including inositol trisphosphate. Formation of inositol trisphosphate appears independent of agonist-induced Ca2+ mobilization, since neither formation nor degradation of inositol trisphosphate are appreciably altered in low-calcium media, and elevation of cytosolic Ca2+ with a calcium ionophore does not cause an increase in cellular inositol trisphosphate. Further, activation of substance P receptors and alpha 1-adrenoreceptors, but not beta-adrenoreceptors, increases inositol trisphosphate formation. The dose-response curve for methacholine activation of inositol trisphosphate formation more closely approximates the curve for receptor occupancy than for Ca2+-activated K+ release. These results are all consistent with the suggestion that inositol trisphosphate could function as a second messenger linking receptor occupation to cellular Ca2+ mobilization.
mesh_terms: D000818:Animals; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000096:biosynthesis* / Q000378:metabolism; D008297:Male; D016210:Methacholine Chloride; D008688:Methacholine Compounds / Q000494:pharmacology; D010306:Parotid Gland / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011976:Receptors, Muscarinic / Q000378:metabolism*; D013403:Sugar Phosphates / Q000096:biosynthesis*
chemical_list: D007295:Inositol Phosphates; D008688:Methacholine Compounds; D011976:Receptors, Muscarinic; D013403:Sugar Phosphates; D016210:Methacholine Chloride; D015544:Inositol 1,4,5-Trisphosphate