Chilling followed by incubation at 37 degrees causes a flow of 3H-choline labeled phospholipids from nuclear-associated endoplasmic reticulum to other endomembranes of L-cells.

The exposure of L-cells to a period of 15 min incubation in ice followed by a return to normal culture conditions caused distinct alterations in the distribution pattern of 3H-choline incorporation in phospholipids in subcellular fractions. The amount of radioactivity appearing in the nuclei and nuclear-associated endoplasmic reticulum decreased while that in the mitochondrial and endoplasmic reticulum membrane fractions increased, suggesting a precursor-product relationship. These changes appeared to occur in a linear fashion. Furthermore, the increase in radioactivity in individual endoplasmic reticulum subfractions differed in that label increased fivefold in light rough membranes but only about twofold in the HR and S subfractions.