Unresponsiveness of phospholipase C to the regulatory proteins Ns and Ni in pancreatic islets.
The possible participation of the regulatory proteins Ns and Ni in the regulation of phospholipase C activity in rat pancreatic islets was investigated. The islets were preincubated for 120 min with myo-[2-3H]inositol and the fractional outflow rate of [3H]inositol or production of [3H]inositol 1-phosphate was then measured. Glucagon failed to affect these metabolic variables, whether in the absence or presence of D-glucose. Pretreatment of the islets with cholera toxin also failed to affect basal or glucose-stimulated [3H]inositol outflow. Likewise, clonidine, which abolished insulin release evoked by D-glucose and carbamylcholine, failed to prevent the stimulant action of these secretagogues upon either [3H]inositol outflow or [3H]inositol 1-phosphate production. It is concluded that the regulatory proteins Ns and Ni apparently do not play any major role in the regulation of phosphoinositide phosphodiesterase activity in islet cells.
D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D003000:Clonidine / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology*; D005934:Glucagon / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D066298:In Vitro Techniques; D007295:Inositol Phosphates / Q000378:metabolism; D007328:Insulin / Q000378:metabolism; D007515:Islets of Langerhans / Q000201:enzymology* / Q000378:metabolism; D007700:Kinetics; D010477:Perfusion; D051381:Rats; D010738:Type C Phospholipases / Q000378:metabolism*
D007295:Inositol Phosphates; D007328:Insulin; D002217:Carbachol; D005934:Glucagon; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D005947:Glucose; D003000:Clonidine