Cyclopentenone prostaglandins(PGs) such as PGA2 and

9-deoxy-9 12.. 1 3, 1 4-dihydro-PGD2(12-PGJ2) are transported actively into the cytoplasm and exert growth inhibition in cultured cells. We examined effect of temperature on the uptake of PGJ2 and its subsequent translocations within and out of the cells. When L-1 21 0 murine leukemia cells were incubated with the PG at 4, 20 and 37#{176} C, the initial rate of uptake increased with temperature. However, the uptake at 37#{176} Cdeclined rapidly after 5 mm, whereas that at 4 and 20#{176} Cincreased linearly and reached plateau. Subcellular distribution study revealed that about 90% of the radioactivity taken up at 4 and 20#{176} Cwas present in the cytoplasm, whereas more than 50% of the radioactivity transported at 37#{176} Caccumulated in the nuclei. When incubation temperature was shifted from 4 to 37#{176} Cduring incu-bation, significant accumulation of the radioactivity in the nuclei occurred at 37#{176} C. In contrast, when the cells were first incubated with 12-PGJ2, then washed and incubated without the PG at either 20 or 37#{176} C, most of the radioactivity found in the cytoplasm was effluxed to the medium during the second incubation. The rate of this efflux was negligible at 4#{176} Cbut increased with temperature above 20#{176} C. These results suggest that L-1 210 cells possess three kinds of temperature-sensitive translocation systems for 12-PGJ2, a carrier-mediated active transport which increases its rate with temperature from 4 to 37#{176} C, an efflux system which is active above 20#{176} Cand a nuclear transfer system which works only at 37#{176} C.