Sequence of Prolactin Effects on Phospholipid Synthesis in Mouse Mammary Gland Explants

Summary

In cultured mouse mammary gland explants derived from 12-14 day pregnant mice, the effect of prolactin (PRL) on the rate of incorporation of several precursors into neutral lipids and phospholipids was determined. Employing [¹⁴C]-acetate as a substrate, PRL stimulates its incorporation into a) neutral lipids by 4-6 hours, b) phosphatidyl choline (PC) and phosphatidyl inositolphosphatidyl serine (PI-PS) by 1-2 hours, and c) phosphatidyl ethanolamine (PE) by 2-4 hours. Using [³H]-glycerol as a substrate, the temporal response to PRL for its incorporation into the neutral lipids was the same as that for [¹⁴C]-acetate, however, PRL did not enhance the rate of [³H]-glycerol incorporation into the phospholipids at any time through 16 hours. PRL similarly had no effect on the rates of [³H]-choline, [³H]-serine, [³H]-ethanolamine, or [³²P]O₄ incorporation into the phospholipids at hormone exposure periods of 8 hours or more. And finally, PRL had no effect on the rates of [³H]-arachidonate or [¹⁴C]-linoleate incorporation into neutral lipids or phospholipids at culture periods up to 18 hours. These data suggest that the early effect of PRL on [¹⁴C]-acetate incorporation into the phospholipids is due to either the insertion of newly synthesized fatty acids and/or the extension of fatty acids contained in the phospholipids.

Key words

Prolactin - Phospholipid Synthesis - Choline - Ethanolamine - Serine - Acetate - Glycerol - Mammary Gland - Arachidonic Acid - Linoleic Acid