We have studied the production and release of cholecystoklnin (CCK) forms by rat medullary thyroid cancer (MTC) in vivo. MTC cells were inoculated s.c. into 8 Wag‐Rij rats. One month later, after i.v. injection of calcium plasma levels of CCK, calcitonin and tissue contents of gastrln and calcitonin were determined by radioimmunoassay (RIA), immunocyto‐chemistry, and high‐pressure liquid chromatography (HPLC). The tumors were passed 4 times to 8 rats in 1‐month intervals fasting levels of CCK in control rats were unaffected by calcium stimulation, and in tumor‐bearing rats, plasma CCK was elevated in 3 out of 4 passages, falling to normal levels at the end of passage 4. Hypercalcemia had no effect on plasma levels of CCK in tumor‐bearing rats, but did stimulate the release of calcitonin in both control and some tumor‐bearing rats in later passages. CCK‐8 sulfate was found in all 4 tumor passages but not CCK‐33/39. We conclude that rat MTC synthesizes and releases CCK‐8, but unlike calcitonin, release of CCK appears unresponsive to calcium stimulation.
ASJC Scopus subject areas
- Cancer Research