In vitro action of PG F 2σ on progesterone and cAMP synthesis in small bovine letual cells

Abstract • The action of prostaglandin F 2 σ (PG F 2 σ) on incubated small bovine luteal cells in the presence or in the absence of bovine luteinizing hormone (LH) or dibutyryl cyclic adenosine monophosphate (db cAMP) was investigated. • In the absence of LH and db cAMP, PG F 2 σ stimulated progesterone synthesis at concentrations of 10 ng/ml and 100 ng/ml but had no effects at concentrations below 1 ng/ml. PG F 2 σ partially inhibited the LH or db cAMP stimulated progesterone synthesis. This inhibition was maximal for PG F 2 σ concentrations around 100 pg/ml whereas distinctly higher or lower concentrations were without effect. At the concentration of 100 pg/ml, PG F 2 σ partially inhibited the LH induced cAMP accumulation. • These results demonstrate an “in vitro” action of PG F 2 σ on bovine luteal cells. They indicate that the luteolytic action of PG F 2 σ in the bovine species could involve, as already suggested for the rat, both an inhibition of the LH induced synthesis of cAMP and on inhibition of the action of cAMP.