Effect of different insulin-secretagogues and blocking agents on islet cell Ca2+-ATPase activity

60. GRONDA, C.M., ROSSI J.P.F.C. Y GAGLIARDINO, J.J.

BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 1988 vol. 943 p. 183 - 189

0005-2736

Plasma raemla.ane Caz+.ATPase activity was meastwed in rat islet homogenates. The enzyme was inhibited,in a dose-del~ndent manner, when the islets were imdncuhated for 5 mln wilh differex~t concentrations ofglucose (2 to 16 raM). This inklhifion disappeared almost enl~rely alter 15 m[n inenbatinn, regardless of theglucose concentration in the medium. Simuitaneotm m,easuRment of insulin in the medium revealed aslimulatory effect of glucose upon insulin secrettom The CaZ+-A'rPase activity was also inhibited whe~ theislets were pt-eincubaeed for 3 mill with other sfnallainrs of insulin secretitm such as glldazide (76 aM),tolbutamide (1-.~ mM), glucagon (1A FM)+ theophylline (10 raM) and ketoisocapmic acid (15 raM).Conversely, the aefivlty of the enz,jme was significantly enhanced when the islets were preinanbatedwith file Insulin seerelinn blocker, somatost~n (1.4 ~tM). Neither giueose nor any el the other substan~tested when added diree'dy to the eazyme assay medinm m~llfled significantly the Cs~+-A'I'P"~,e aetivilymeasm~ in the islet homogenates. The~, remits would mggest that the activity of the islet plasmamembrane is modulated by one or move ef the intracelinlar metabolites pmdmed when the islets arechallenged by the insnlin stlmulatm' or I~ddng agents.