[Relaxin and cervical dilatation during parturition (author's transl)]

Relaxin concentrations during pregnancy and parturition were measured in tissue specimens of the uterine cervix of 27 women in childbearing age. During pregnancy relaxin levels increase from 0.4 guinea pig unit (GPU) to 0.94 GPU/mg soluble tissue protein. Already during parturition (0.41 GPU) and immediately post partum (0.39 GPU) the hormone concentrations have dropped back to normal. It appears that the biochemical changes which occur in the connective tissue of the uterine cervix during pregnancy and parturition are influenced by relaxin. Experimental animals were taken to show if relaxin acts by activation of collagenolytic enzymes. In the mouse a rise in the activity of collagen-peptidase and of the inhibitor of collagen-peptidase in plasma was found after subcutaneous injections of relaxin. The addition of human cervical tissue extracts resulted in an increase of enzyme-activation (even higher than could be expected of the hormone concentrations of the individual extracts). The highest levels of the enzyme were found after injections of extracts from cervical tissue specimens of parturient women.