Objective: To investigate the capacity of the human corpus luteum (CL) of pregnancy to form cyclic adenosine-3',5'-monophosphate (cAMP) and P in vitro in response to hCG and prostaglandin (PG) E2.
Design: Six women undergoing sterilization concomitant with legal abortion and eight women undergoing surgery for ectopic pregnancy were included. Human chorionic gonadotropin was analyzed preoperatively in two serum samples. The CL were excised and luteal specimens were incubated for 2 hours in the presence or absence of hCG or PGE2. The tissue concentrations of cAMP and P concentrations in the incubation media were measured. The in vitro results were correlated to the preoperative daily change in serum hCG.
Results: In CL from pregnancies with normally rising serum hCG levels, the addition of hCG in vitro did not affect luteal cAMP or P production. In pregnancies with plateauing and/or decreasing serum hCG levels, the addition of hCG in vitro significantly stimulated cAMP and P formation, and this stimulatory effect correlated significantly with the preoperative daily change in serum hCG. In contrast to hCG, PGE2 had the same stimulatory effect in vitro on CL specimens from both normal and pathological pregnancies. This effect did not correlate with the preoperative daily change in serum hCG.
Conclusions: Prostaglandin E2 stimulates all CL, irrespective of any changes in preoperative serum hCG levels. In contrast, the stimulatory effect of hCG in vitro does not correlate with changes in serum hCG, and thus CL from pregnancies with normally rising serum hCG levels are refractory to hCG in vitro.