Inhibition of FSH-stimulated cAMP accumulation and progesterone production by mono(2-ethylhexyl) phthalate in rat granulosa cell cultures

Abstract

Several phthalate esters are male and female reproductive toxicants in vivo. In the male, mono(2-ethylhexyl) phthalate (MEHP), the active metabolite of di(2-ethylhexyl) phthalate (DEHP), inhibits follicle stimulating hormone (FSH)-stimulated cAMP accumulation in the Sertoli cell in vitro. Since granulosa and Sertoli cells share several structural and functional characteristics, the effect of MEHP on granulosa cell intracellular cAMP accumulation was examined to elucidate a possible mechanism for DEHP reproductive toxicity in females. MEHP (100 μ m) reduced FSH-stimulated cAMP accumulation in granulosa cells by 40% after a 24-hr preincubation. Significant inhibition of cAMP accumulation by MEHP occurred by 15 hr and MEHP did not affect the dose of FSH which resulted in half-maximal stimulation. Detailed investigations regarding the mechanism of MEHP inhibition were conducted using cholera toxin, forskolin, and isoproterenol. In contrast to FSH, MEHP did not affect the ability of these compounds to stimulate cAMP accumulation. In addition, a functional endpoint of granulosa cell function, progesterone production, was inhibited in a dose-dependent manner by MEHP. Further experiments will be necessary to determine the significance of these findings to in vivo toxicity, but these experiments describe a specific site of action of MEHP in vitro which may be related to the in vivo female reproductive toxicity of phthalate esters.