Activation of guanyl cyclase and adenyl cyclase by secretin

摘要: Abstract Properties of rat liver guanyl cyclase and adenyl the effects hormones on activity these enzymes have been investigated. 1. Secretin ( 2·10 −7 –60·10 M ) stimulates 18 000 × g supernantants homogenates with no change in Michaelis-Menten constant for GTP 3.8·10 −5 ). 2. Insulin, glucagon, hydrocortisone vitro were found to effect presence or absence secretin. 3. p- Chloromercuriphenyl sulfonate inhibits activity, chloromercuriphenyl inhibition is reversed by dithiothreitol. sulfonate-dithiothreitol treatments sensitivity enzyme secretin stimulation. These studies indicate that sulfhydryl groups may be involved regulation cyclase. 4. Adenyl homogenate stimulated approximately 50% stimulation caused glucagon. Using hormone concentrations maximally stimulate cyclase, experiments combinations secretin, isoproterenol only do not additive effects. Propranolol blocks due isoproterenol, but does affect 5. Insulin has either glucagon- secretin-stimulated activity.