Human milk does not degrade TRH

We have found previously that TRH is accumulated in rat milk in biologically active form. TRH was reported to be present in high concentrations in human milk too. These findings together with the absence of TRH degrading activity in plasma of newborns suggest a possible physiological role of the neurohormone coming from milk. We studied, therefore, TRH degrading activity of human milk. TRH incubated in vitro with 100 microliters human milk (4 days and 4 months after delivery) in 0.01 mol l-1 phosphate saline buffer (pH 7.6) with 1% gelatine (total volume 0.3 ml) at 37 degrees C was not degraded during 2 hours as revealed by specific RIA. The addition of the same amount of milk to adult human plasma did not affect intensive TRH degradation. We conclude that human milk does not contain TRH degrading enzymes nor their inhibitors.