Endorphin activity in cerebrospinal fluid prior to elective cesarean section and in early puerperium.

Opioid activity in cerebrospinal fluid (CSF) was estimated by radioreceptor-assay (RRA) in samples obtained from ten women at term pregnancy and in the early puerperal period. The samples were fractioned on Sephadex G-10 columns and two opioid receptor active fractions, FI and FII, were recovered. Two pools of FII materials from pregnant and puerperal women, respectively, were further analyzed by electrophoresis and the concentrations of opioid activity were measured by radioreceptor assay. There was a significant rise in receptor-assayed FII opioid activity in late pregnancy as well as in the early puerperal period compared to that of healthy, nonpregnant, nonpuerperal females. Pooled FII material obtained before delivery could be separated into two major components tentatively assigned the hexapeptide [Met]enkephalin-Lys6 and the heptapeptide [Met]enkephalin-Arg6-Phe7. These two opioid peptides both have their origin in the [Met]enkephalin precursor, proenkephalin A. In the puerperal period there was predominance of only one of these components.