Synthesis of prostaglandins in cholera toxin-treated Chinese hamster ovary cells

The prostaglandin (PG) and adenosine 3′,5′-cyclic monophosphate (cAMP) responses of Chinese hamster ovary (CHO) cells were measured after cholera toxin (CT) exposure to evaluate dose and kinetic relationships. Release of prostaglandin E₂ (PGE₂) and the accumulation of cAMP were dependent on the dose of CT, with an effective dose of approximately 10-100 ng/ml within 4 h; the PGE₂ response was about four- to six-fold more than that of PGE₁. CHO cells exposed to CT also released increased amounts of thromboxane B₂ (TxB₂), PGF_2α, and 6-keto PGF_1α (a non-enzymatic degradation product of prostacyclin). Kinetic analysis of CT-treated cells revealed that small peaks of cAMP accumulation and of PGE₁ and PGE₂ release were detected at approximately 30 min, but larger, progressive PG and cAMP responses were measured 2-4 h later. Exposure of the cells to relatively high doses of membrane-permeable derivatives of cAMP (1 mm) and forskolin (10 μm) caused PGE₂ release. Concomitantly, exogenous PGE₂ (100 μm) increased intraceliular levels of cAMP. We have considered the interrelationship of the cyclo-oxygenase and the cyclic nucleotide pathways relative to the molecular mechanism of CT.