Little is known about matrix metalloproteinases (MMPs), enzymes that are required for the structural remodeling and angiogenesis that occur in the corpus luteum (CL) during the first several days postovulation. In fact, little attention has focused on early CL function including the regulation of progesterone (P4) production. Thus, the objective of the present study was 1) to investigate the effects of insulin, LH, and dibutyryl cAMP on P4 production and cell numbers and 2) to identify MMPs in the 4-day-old CL, with use of a defined culture system. Cultures were seeded with either 1 x 10(6) or 0.5 x 10(6) cells. All cultures containing insulin had higher P4 levels and cell numbers (p < 0.05) than those without. In cultures containing insulin, basal P4 levels were high throughout the culture period. Furthermore, neither LH nor dibutyryl cAMP stimulated P4 production (p > 0.05) at a seeding density of 1 x 10(6), whereas they stimulated P4 production (p < 0.05) at a seeding density of 0.5 x 10(6) on Days 6 and 8 of culture. In conditioned medium of control cultures seeded with 0.5 x 10(6) cells, substrate gel electrophoresis (zymography) showed two intense bands that migrated at M(r) approximately 97,000 and approximately 65,000-64,000, while two weaker ones migrated at M(r) approximately 88,000 and approximately 64,000-63,000. The molecular weights of the M(r) approximately 97,000 and approximately 88,000 species were consistent with MMP-9 family members, while the molecular weights of the M(r) approximately 65,000-64,000 and approximately 64,000-63,000 species were consistent with MMP-2 family members.(ABSTRACT TRUNCATED AT 250 WORDS)
