Prostaglandin E2-binding sites and cAMP production in porcine fundic mucosa

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Abstract
Biologically active [3H]prostaglandin E2 (PGE2) bound rapidly and specifically to membrane fractions from hog fundic mucosa. Optimal binding occurred in the 30,000-g membrane preparation at 37.degree. C (pH 5.0). Scatchard analysis of specific PGE2 binding revealed the presence of a heterogeneous population of binding sites with Kd values and binding site concentrations of approximately 1 .times. 10-9 M and 1 f[femto]/mg protein and 2 .times. 10-8 M and 20 fmol/mg protein, respectively. Specific binding was inhibited by the following agents in descending order of potency: PGE1, PGA2, PGD2, 6-keto-PGF1.alpha. and thromboxane B2. Trypsin treatment or boiling reduced or abolished specific PGE2 binding. PGE2 stimulated cAMP formation in the 2,500-g fraction, with an approximate Km of 1 .times. 10-6 M, but stimulation of adenylate cyclase activity by PG was not evident in the 16,000-g or 30,000-g tissue preparations. Evidently, a specific PGE2-binding site exists in the 16,000-g and 30,000-g fractions of porcine fundic mucosa, although an increase in cAMP-forming capacity could not be localized in these fractions in vitro.