Effect of modulators of cytoskeletal function on desensitization and recovery of PGE2-responsive ovarian adenylate cyclase.

Exposure of cultured Graafian follicles to PGE2 for 20 h resulted in a loss of the cyclic AMP response to fresh hormone. This desensitization was prevented by addition to the medium of D2O (25--50%) or Li+ (0.6--6 mM), agents believed to stabilize microtubules, as well as by phalloidin (1.0--10 microM), believed to stabilize the polymerized state of actin, in a dose-dependent manner. The spontaneous recovery of responsiveness to PGE2 upon incubation of refractory follicles for 6 h in hormone-free medium was prevented by addition to the medium of cytochalasin B (CB; 3 microgram/ml) or of the actin-binding myosin subfragment HMM S-1 (80 microgram/ml) or of anti-actin serum; viz. by agents likely to interfere with microfilament function. D2O (50%) caused morphological damage to the inner layer of the membrana granulosa and severe depression of protein synthesis. The other drugs used (phalloidin, LiCl and cytochalasin B) had no such effects. Resensitization of refractory follicles was also prevented by cycloheximide (10 micrograms/ml) and by actinomycin D (10 micrograms/ml). It is speculated that the recovery process may involve the insertion of a newly synthesized protein, such as PG-receptor, into the membrane by a mechanism dependent on microfilament action. These findings provide suggestive evidence for the hypothesis that cytoskeletal elements associated with the cell membrane take part in the modulation of the adenylate cyclase response to hormones.