Abstract
Mammary carcinomata were induced by administration of nitrosomethyl urea to female Buffalo rats. Specific binding of PGE 1 to the 15,000xg membranes obtained from these tumors was maximal after ∼ 60 minutes of i cubation at 15°C. An excess of unlabeled PGE 1 dissociated 50% of the [ 3H]PGE 1 from the membrane within 15 minutes. The binding of [ 3H]PGE 1 was inhibited by various prostaglandins in a concentration-dependent manner, the order of potency being PGE 1>PGE 2>PGA 2>PGF 2α>PGB 2. High affinity receptor sites were not definable by Scatchard analysis until 5mM CuCl 2 was added. This resulted in the detection of both high and low affinity receptors (K d= 1.01 nM and 21 μM) having binding capacities of 29 and 357 fmole/mg protein, respectively. Addition of CaCl 2 or MgCl 2 did not result in a significant increase in the specific binding of PGE 1 to the receptors. These studies provide a means by which high affinity prostaglandin E 1 receptors can be detected in neoplastic tissue and suggest a mechanism by which copper ions can increase the effect of PGE 1 in tissues.
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