Abstract: 19

OXIDIZED-LOW DENSITY LIPOPROTEIN INHIBITS CYCLIC AMP PRODUCTION IN PORCINE LUTEAL CELLS.

John Brannian^{1 *}, Carla Rickert^{1 *}
Dept. of OB/GYN, University of South Dakota, Sioux Falls, SD, USA ¹

OX-LDL inhibited steroidogenesis in luteal cell (LC) cultures from regressing porcine CL [BOR 1997; 56:221]. The present study was designed to determine whether OX-LDL inhibited hCG-, cholera toxin (CT)-, and forskolin (FS)-stimulated cAMP production in regressing LC. Collagenase-dispersed pig LC (n =7 animals, estrous cycle day 13-16) were cultured (2.5 × 10⁵ cells/0.5 ml) in ITS-supplemented DMEM/Hams F-12 in duplicate wells at 37°ree;C. Approximately 18 h after plating, media were replaced and LC were immediately treated with human LDL (0, 25, or 100 µg/ml; Sigma, St. Louis, MO) or OX-LDL (25 or 100 µg/ml; BTI, Stoughton, MA). LC were incubated for 2 h before addition of isobutylmethylxanthine (IBMX) to inhibit phosphodiesterase activity, immediately followed by hCG (100 ng/ml; CR-127), CT (0.1 µM; Sigma), FS (50 µM; Sigma), or no further treatment (controls). LC were incubated for an additional 90 min. After removal of culture media, cells were extracted by addition of 0.1 N HCl (0.25 ml) to each well for 15 min. Cell extracts were assayed for cAMP by EIA (R & D Systems, Minneapolis, MN). HCG, CT, and FS increased (p< 0.05) cAMP production approximately 4-, 10-, and 25-fold, respectively, relative to controls. OX-LDL (25 and 100 µg/ml) inhibited (p < 0.05) cAMP production by untreated, hCG-, and CT-stimulated LC, but not that by FS-stimulated LC. The highest concentration of OX-LDL (100 µg/ml) reduced cAMP formation by 39.9±6.7%, 44.7±10.5%, and 67.7±4.9% in untreated, hCG-, and CT-stimulated LC, respectively. In contrast, unmodified LDL (25 and 100 µg/ml) did not alter cAMP production. We conclude that OX-LDL can interfere with the cAMP signaling pathway in regressing luteal cells by acting at sites proximal to adenyl cyclase activation. [NSF OSR-9452894,NICHD grant HD-35333]

    This abstract is being presented on Sunday, August 1 at 8:00 AM to 10:15 AM at CUB 2nd Floor Ballroom.