Metabolism of phospholipid in mammary gland: I. The supply of phospholipid for milk synthesis in the rat and goat

Data presented in this study demonstrate that under normal physiological conditions milk phospholipids in the rat and the goat originate predominantly, if not totally, by de novo synthesis within the mammary gland. Evidence to support this has been obtained for the goat by measurement of P³²-phosphate incorporation into milk phospholipids, and in the rat by measurement of P³²-phosphate incorporation and by feeding radioactive phospholipid to measure the incorporation of serum phospholipids into milk. The latter experiment showed that the fatty acid portion of the dietary phospholipid can readily be utilized by the mammary gland for triglyceride synthesis, but that the contribution of the serum phospholipid “backbone” to milk phospholipid is minimal.