SITE AND MECHANISM OF GROWTH-INHIBITION BY PROSTAGLANDINS .1. ACTIVE-TRANSPORT AND INTRACELLULAR ACCUMULATION OF CYCLOPENTENONE PROSTAGLANDINS, A REACTION LEADING TO GROWTH-INHIBITION

  • 1 November 1986
    • journal article
    • research article
    • Vol. 239  (2) , 500-505
Abstract
Cyclopentenone prostaglandins (PGs) such as PGA2 or 9-deoxy-.DELTA.9.12-13,14-dihydro-PGD2 (.DELTA.12-PGJ2) induce growth inhibition of various lines of cultured cells. Action sites of these PGs were studied by incubating them with L-1210 murine leukemia cells. L-1210 cells accumulated both PGs in a time-dependent manner at 37.degree. C. When the uptake was analyzed with various concentrations of .DELTA.12-PGJ2, the Michaelis-Menten type of kinetics was obtained, and the Km and Vmax were 250 .mu.M and 2.5 nmol/min/106 cells, suggesting that the uptake was a carrier-mediated active transport. Competition studies with [3H].DELTA.12-PGJ2 showed that PGA2 was transported by the same carrier with a similar affinity. PGs without growth inhibitory activity such as PGD2, PGE2 and PGF2.alpha. were neither taken up by the cells nor interferred the uptake. Subcellular distribution studies with sucrose density gradient centrifugation showed that transported .DELTA.12-PGJ2 was present mainly in cytoplasm and nuclei without metabolism. Accumulation of the PG was attenuated greatly by preincubation of the cells at 37.degree. C for 30 min. When the effect of .DELTA.12-PGJ2 was examined in the control and attenuated cells, a clear correlation was observed between the accumulation of the PG and its growth inhibitory effect. These results suggested that uptake and intracellular accumulation of cyclopentenone PGs are responsible for their growth inhibitory activity.