Effect of estradiol on pancreatic amylase and cholecystokinin binding in ovariectomized guinea pigs

The effect of estradiol (E₂) on amylase content and on basal and stimulated amylase release from the pancreatic acini was examined in relation to its effects on cholecystokinin (CCK)-receptor (R) levels. Guinea pigs were ovariectomized (OVX) and a week later administered either E₂ (10 μg/kg) (Treated, T) or vehicle (corn oil) (Control, C) 0.2 ml/day s.c. After 7 days of injections, animals were killed, pancreata weighed and basal and stimulated amylase release from pancreatic acini measured. Receptors for CCK were measured on pancreatic membranes. Chronic administration of E₂ resulted in a significant decrease in: (1) pancreatic weight (0.96 ± 0.04, T vs 1.142 ± 0.046 g, C); (2) total pancreatic DNA content (5.74 ± 0.37, T vs 6.81 ± 0.16 mgs, C); (3) total amylase content in pancreata (2081 ± 307, T vs 3795 ± 442 I.U., C); (4) absolute value of basal amylase release (6.57 ± 1.4, T vs 11.8 ± 1.9 I.U./incubate, C); and (5) absolute value of amylase release stimulated by increasing doses (0.01-1000 nM) of CCK in T vs C animals. On the other hand, the amylase release in response to >0.5 nM of CCK, expressed as a percentage of the total amylase content, was significantly increased in T vs C animals, which may be related to a significant rise in the concentration (fmol/mg protein) of CCK-receptors (629.8 ± 65.9, T vs 313.4 ± 92.7 fmol, C). Concentration of DNA/unit pancreatic weight and basal amylase release expressed as a percentage of total content, however, was similar in the C and T guinea pigs, while concentration of amylase and CCK-receptors/unit pancreatic weight remained significantly different in the two groups of animals. These results suggest that E₂ may have more than one effect on the pancreas in vivo, including a significant reduction in pancreatic growth and amylase concentration/cell and an up-regulation of CCK-receptors/cell.