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The peptide hormone cholecystokinin (CCK) has been shown to stimulate the growth of azaserine-induced preneoplastic nodules in the rat pancreas. Previously, our laboratory demonstrated by classical binding studies that CCK receptors are overexpressed in azaserine-induced rat pancreatic neoplasms. In the present study, we utilized autoradiography to determine the temporal course of this increased receptor binding. Male Lewis rats were given azaserine or saline injections and sacrificed at 2, 4, 8, 12, and 18 months of age. Pancreatic tissue was harvested and autoradiography using 125I-labeled- CCK-8 was performed. Densitometry measurements of azaserine-induced pancreatic nodules, internodular pancreas, and normal pancreatic tissue (from saline-treated controls) of each age group were taken with an image analyzer. There was no statistically significant difference in CCK binding to internodular pancreas and normal pancreas at any age. At 2 months of age, there was no significant increase in CCK binding to azaserine-induced pancreatic nodules. However, at 4, 8, 12, and 18 months of age there was significantly greater CCK binding to azaserine-induced pancreatic nodules than to both internodular pancreas and normal pancreas (p< 0.001 for all groups). At 18 months of age, one azaserine-treated animal developed a pancreatic acinar cell carcinoma, which likewise exhibited significantly greater CCK binding than internodular pancreas or normal pancreas (p< 0.001 for both). These findings demonstrate increased CCK binding in azaserine-induced preneoplastic pancreatic nodules and pancreatic acinar cell carcinoma, compatible with our previous demonstration of receptor overexpression in these tissues. Increased CCK binding first becomes apparent by 4 months following exposure to azaserine. These results suggest that overexpression of CCK receptors, located specifically on preneoplastic and neoplastic pancreatic lesions, results in increased CCK binding and is involved in the mediation of CCK-stimulated growth during azaserine-induced pancreatic carcinogenesis.

Purified preparations of normal C1¯-inhibitor (C1¯-INH) formed high mol wt complexes with plasma kallikrein that were stable during sodium dodecyl sulfate (SDS)-gel elec-trophoresis, but most of the dysfunctional C1¯-INH proteins isolated from plasma of patients with type II hereditary angioneurotic edema (HANE) did not. Two of eight dysfunctional C1¯-INH proteins were cleaved to lower mol wt forms that were not seen following the reaction of normal C1¯-INH with equimolar amounts, or less, of plasma kallikrein. Only the higher mol wt component of normal C1¯-INH (106,000 mol wt) appeared to form a stable complex with the plasma kallikrein, whereas both the 106,000 and 96,000 mol wt forms made stable complexes with C1s¯. When a preparation of normal C1¯-INH containing a homogeneous single band of C1¯-INH was exposed to C1s¯or kallikrein, a “doublet” form evolved in which the heaviest band was in the original position of native C1¯-INH; C1s¯cleavage provided a second band of 96,000; and cleavage by kallikrein, a second band of 94,000 mol wt. We conclude that dysfunctional C1¯-INH proteins from plasma of persons with type II hereditary angioneurotic edema have impaired interactions with plasma kallikrein and are heterogeneous with respect to these interactions. Moreover, the requirements for the formation of stable complexes between normal C1¯-INH and plasma kallikrein differed from those for stable complex formation with C1s¯. The doublet form of C1¯-INH, which purified preparations frequently demonstrate, may be due to prior cleavage by C1s¯or kallikrein.