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 degrees 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 X 10(-9) M and 1 fmol/mg prot and 2 X 10(-8) M and 20 fmol/mg prot, 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 X 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. These results suggest that 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 b of 1 X 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. These results suggest that 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 b of 1 X 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. These results suggest that 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.
Characterization of (-)-[3H]dihdroalprenolol binding sites on isolated rat fat cells.
