Activation of probable proinsulin-converting enzymes in pancreatic islets: its correlationship with rate of insulin biosynthesis
Chatterjee, A.K.; Mukherjee, S.K.
Indian Journal of Experimental Biology 22(8): 435-438
1984
ISSN/ISBN: 0019-5189 PMID: 6392078 Document Number: 238022
A rise in concentration of glucose from 0 to 11.0 and 16.7 mM incubation medium caused a graded increase in the formation of labeled (pro) insulin as well as in the activities of acid phosphatase and cathepsin-B of rat pancreatic islets. However, sorbose and pyruvic acid at 2 different concentrations (16.7 and 22.2 mM: 20.0 and 33.3 mM) failed to bring any alteration in the basal level of (pro) insulin synthesis although, only pyruvic acid caused a little increase in acid phosphatase and a significant increase in cathepsin-B activities. Identical concentration (0.1 mM) of 2 oral antidiabetic compounds-phenformin and tolbutamide was also found to fail in stimulating insulin biosynthesis as well as in any of the enzyme activities. To the contrary, alloxan and streptozotocin at optimum concentrations of 1.25 and 2.2 mM, respectively, lowered significantly the rate of synthesis of (pro) insulin and the activities of the 2 enzymes. Thus, a positive correlationship between the rate of insulin formation and activities not only of acid phosphatase but also of cathepsin-B of pancreatic islets was established.