Concentration of Prolactin, Growth Hormone and ACTH in Blood and Tumor of Rats with Transplantable Mammotropic Pituitary Tumors

Transplantable mammotropic pituitary tumors from Fisher rats during 9 transfers were lyophilized and assayed for prolactin, growth hormone and ACTH activity. Blood plasma from the same rats was also collected and assayed. Prolactin concentration in tumors averaged 3.5 units/g dry wt, which is 3 % of that in the normal pituitary. The plasma level was 1 unit/ml or 10 units/ g dry wt. This is more than 50 times the level in normal plasma. And the plasma powder was more potent than the tumor powder per unit of weight. Growth hormone concentration in tumors averaged 4 units/g dry wt, which is 14% of that in the normal pituitary. The plasma level was 30 mU/ml, which is 30 times the level in normal plasma. ACTH concentration in tumors averaged 7 units/g dry wt, which is 3 % of that in the normal pituitary. The plasma level was 60 mU/ml, which is 6,000 times that in normal human plasma. The ratio of total potency in the tumor to total potency in plasma was 62 for growth hormone, 36 for ACTH and only 1.2 for prolactin. This suggests that growth hormone and ACTH accumulate to an appreciable concentration in tumor tissue, whereas prolactin is not stored. The high plasma levels of all hormones indicate a good rate of hormone production by the tumor tissue.