The developmental accumulation of gamma-glutamyl transferase in the pancreas of the rat.

The developmental accumulation of pancreatic exocrine secretory enzymes is well defined, but little is known of the development of other enzymes in the pancreas. This report focuses on the developmental accumulation of gamma-glutamyl transferase (GGT), a membrane-bound ectoenzyme whose specific activity in the pancreas is the second largest among rat organs. GGT activity is large in organs with active glutathione metabolism. Pancreatic GGT specific activity increased 100-fold from prenatal day 14 to birth, decreased 3-fold until about postnatal week 2, and then increased until the adult value was reached 4 weeks after birth. There was a 500-fold increase in specific activity from prenatal day 14 to the adult. The developmental accumulation pattern of GGT was very similar to that of the exocrine secretory enzyme amylase, which increased 1,300-fold from prenatal day 14 to birth, decreased 8-fold by postnatal week 1, and then increased to the adult level soon after week 4. The overall increase in amylase specific activity was 1,100-fold. The similar developmental accumulation patterns of GGT and amylase suggested that their accumulation might be regulated in a similar fashion. Although the thymidine analogue 5-bromodeoxyuridine inhibited the prenatal accumulation of amylase, as previously reported, it did not inhibit prenatal GGT accumulation. Therefore, the prenatal accumulation of GGT appears to be regulated differently than amylase. On the other hand, the postnatal levels of GGT appear to be controlled by glucocorticoids in a fashion similar to the previously reported control of amylase levels, since both enzymes could be induced to rise prematurely to adult levels by a series of three injections of the glucocorticoid dexamethasone beginning on days 7, 8, 9, 10, 11, or 12.(ABSTRACT TRUNCATED AT 250 WORDS)