Figure 4.

PDE4, PDE7, and PDE8 all contribute to suppression of spontaneous production of progesterone and PGRs. (A and B) Time course of synthesis of (A) progesterone and (B) its receptors, PGR-A and PGR-B, in response to LH (300 nM). (C–F) Stimulation of synthesis of (C) progesterone and (D–F) PGRs by incubation of follicles for 6 hours in the presence of LH (300 nM) or PDE4i (rolipram, 5 μM), PDE7i (1 μM), and/or PDE8i (1 μM). (B and D) Molecular weight in kDa is shown at left. The doublet near the 97 kDa marker corresponds to the PGR-A isoform, and the doublet just above the 116 kDa marker corresponds to the PGR-B isoform; the doublets are thought to result from phosphorylation (32). The lower bands, in the range of ∼50 to 70 kDa, are unidentified but have been seen in a previous study as well (32). Numbers in parentheses indicate the number of independent experiments. Different letters indicate significant differences (P < 0.05).