Relaxin receptors in the human female anterior cruciate ligament.
BACKGROUND
Noncontact anterior cruciate ligament injuries occur two to eight times more often in women than in men. Changes in ligament laxity and strength have been associated with female hormones such as relaxin.


OBJECTIVE
Relaxin receptors are present within the female anterior cruciate ligament.


METHODS
Controlled laboratory study.


METHODS
Remnants of anterior cruciate ligament were harvested from five women and five men undergoing routine ligament reconstruction. Relaxin was biotinylated and analyzed for biologic activity with use of the mouse interpubic ligament bioassay. Immunohistochemical localization of relaxin receptors was performed with appropriate negative controls and competitive binding assays to determine receptor specificity and saturability.


RESULTS
Anterior cruciate ligament sections from women but not from men showed uniform specific binding that was limited to synovial lining cells, stromal fibroblasts, and cells lining blood vessels. Specific binding was confirmed in the presence of a 2000-fold excess of human insulin, the structural homolog of relaxin, and competitive inhibition was demonstrated in the presence of a 2000-fold excess of unlabeled relaxin.


CONCLUSIONS
Relaxin exhibits specific saturable binding in the female anterior cruciate ligament, where specific relaxin receptors were present.


CONCLUSIONS
The high incidence of anterior cruciate ligament rupture in female athletes may be partially explained by the effects of relaxin.
Dragoo
Jason L
JL
Department of Orthopaedic Surgery, University of California Los Angeles School of Medicine, Los Angeles, California 90095, USA.
Lee
Richard S
RS
Benhaim
Prosper
P
Finerman
Gerald A M
GA
Hame
Sharon L
SL
D000293:Adolescent; D000328:Adult; D016118:Anterior Cruciate Ligament / Q000378:metabolism*; D000070598:Anterior Cruciate Ligament Injuries; D001265:Athletic Injuries / Q000378:metabolism; D005260:Female; D006801:Humans; D008297:Male; D043562:Receptors, G-Protein-Coupled; D018000:Receptors, Peptide / Q000378:metabolism*; D012421:Rupture / Q000378:metabolism; D012737:Sex Factors
D043562:Receptors, G-Protein-Coupled; D018000:Receptors, Peptide; C033395:relaxin receptors