Evidence for Proteolysis during Purification of Relaxin from Pregnant Sow Ovaries

Publisher Website
Google Scholar
Abstract
The proteolytic degradation of relaxin during its isolation from pregnant sow ovaries has been examined. Ovaries from pregnant sows were selected and divided into three groups according to the stages of pregnancy. Each group was extracted with and without protease inhibitors. It was found that protease(s) were present in all groups of ovaries and that a 2–4 fold increase in yield of total relaxin was obtained when isolation and purification was carried out in the presence of protease inhibitors. However the ratio of the three forms of relaxin remain unchanged. Relaxin is a small peptide hormone (M.W. 6,300) which relaxes the pubic symphysis, inhibits spontaneous uterine contractions, softens and dilates the cervix, and stimulates the development of mammary glands (1). Porcine relaxin has been successfully purified from pregnant sow ovaries (2). Three components, namely, CM-B, CM-a and CM-a' were obtained according to their order of elution from a CM-cellulose column. Although chemical structures for porcine relaxin have been proposed (3, 4, 5, 6), the structural differences among the three components of relaxin have not yet been established. In addition two other laboratories have used different isolation methods and have also shown three species of relaxin present in pregnant sow ovaries (7, 8). Hence there has been discussion on whether there are a number of relaxin(s) or isohormones (9). The purpose of this study was to examine the possibility that proteolytic degradation of the stored form of relaxin during the isolation procedure could explain the heterogeneity found by several isolation methods. In our attempt to control proteolysis during relaxin isolation we noted increased yields of relaxin although the ratio of the three components CM-B, CM-a and CM-a' were essentially unchanged, suggesting either that they are endogenous components or that proteolysis may still be taking place during isolation. The increased yields of total relaxin which were obtained regardless of the stage of pregnancy of the ovaries used is of particular value when isolation is from tissues in which the relaxin content is much lower than in pregnant sow ovaries.