Proton NMR spectroscopy of the phospholipids in human uterine smooth muscle and placenta

The parameters regulating the fluidity of myometrial and placental phosphol ipids include double bonds, fatty acid chain length and the cholesterol/pho spholipid ratio. The transformation of these parameters was studied during pregnancy and labor. Myometrial and placental tissue samples were collected from 24 patients: 6 were nonpregnant, 6 early-pregnant, 6 late-pregnant no t in labor and 6 in labor. After butanol extraction, tissue cholesterol and lipid phosphorus were determined. Proton NMR spectroscopy of the phospholi pids was performed at 500 MHz. The myometrial cholesterol/phospholipid rati o was slightly elevated in pregnant patients not in labor. The uterine musc le of the nonpregnant patients contained more CH=CH groups in the phospholi pids than that of the late-pregnant patients. There were 29 more double bon ds in placental than in uterine tissue per 100 fatty acid molecules. The av erage fatty acid chain length varied from 14.0 to 18.8. The placenta has lo nger fatty acid chains than the uterine smooth muscle. The myometrial carbo n chain was shortened on the average by 1.4 and the placental by 1.0 carbon atoms, when the patient went into clinical labor. These findings suggest f luidity changes in myometrial and placental phospholipids during human preg nancy and labor.