Bioassays for relaxin and relaxin-related peptides

Abstract

The bioactivity of relaxin, isolated as native peptide from the ovaries of various species and synthesised as the peptide predicted from gene sequence, has been characterised in several functional bioassays. The in vivo guinea pig pubic symphysis palpation [1] and the mouse interpubic ligament [2] bioassays are well documented to measure relaxinlike activity. However, these bioassays are expensive, cumbersome and require a large number of animals to obtain a dose-response relationship. The isolated atrial bioassay is a more recently developed functional bioassay [3], where relaxin produces dose-dependent positive chronotropic and inotropic responses in rat right and left atria respectively. The isolated atrial assay is relatively easy to set up and since a complete dose response curve can be completed in a single preparation, it allows the dose-response relationship of relaxin to be determined with small numbers of animals. In this study, we have used the isolated rat atrial bioassay and a quantitative autoradiographic binding assay using rat atrial sections [4] to characterise the bioactivity of human, porcine and rat relaxin analogues. To assess the interaction of relaxin analogues with a human relaxin receptor, we used a receptor binding assay with human THP-1 cells [5].