title: Changes in Knee Laxity and Relaxin Receptor Isoforms Expression (RXFP1/RXFP2) in the Knee throughout Estrous Cycle Phases in Rodents.
abstract: The changes in knee laxity and relaxin receptor expression at different phases of rodent estrous cycle are not known. Here, changes in the parameter were investigated in rats at different phases of the estrous cycle. Estrous cycle phases of intact female rats were determined by cytological examination of the vaginal smear. Following phase identification, blood was collected for serum hormone analyses. Knee passive range of motion (ROM) was determined by using a digital miniature goniometer. The animals were then sacrificed and patellar tendon, collateral ligaments and hamstring muscles were harvested for relaxin/insulin-like family peptide receptor 1 and 2 (RXFP1/RXFP2) analyses. Knee passive ROM was the highest at proestrus followed by diestrus and the lowest at estrus. Estrogen level was the highest at proestrus while progesterone and relaxin levels were the highest at diestrus. A strong correlation was observed between relaxin and progesterone levels. At proestrus, expression of RXFP1 and RXFP2 proteins and mRNAs were the highest at proestrus followed by diestrus and estrus. The finding shows that higher level of progesterone and relaxin in diestrus might be responsible for higher laxity of knee joint in rats.
authors: Department of Exercise Physiology, Faculty of Physical Education and Sport Sciences, University of Tehran, Tehran, Iran.|Department of exercise science, Sports Center, University of Malaya, Kuala Lumpur, 50603, Malaysia.
authors: Firouzeh
authors: F
authors: Dehghan
authors: Department of Exercise Physiology, Faculty of Physical Education and Sport Sciences, University of Tehran, Tehran, Iran.
authors: Rahman
authors: R
authors: Soori
authors: Health Deputy, Babol University of Medical Sciences, Babol, Iran.
authors: Parvin
authors: P
authors: Dehghan
authors: Department of Physiology, Faculty of Medicine, University of Malaya, Kuala Lumpur, 50603, Malaysia.
authors: Khadijeh
authors: K
authors: Gholami
authors: Department of Molecular Medicine, Faculty of Medicine, University of Malaya, Kuala Lumpur, 50603, Malaysia.
authors: Sekaran
authors: S
authors: Muniandy
authors: Department of Physical Education and Sports Sciences, Central Tehran Branch, Islamic Azad University, Tehran, Iran.
authors: Mohammad Ali
authors: MA
authors: Azarbayjani
authors: Department of exercise science, Sports Center, University of Malaya, Kuala Lumpur, 50603, Malaysia.
authors: Ashril
authors: A
authors: Yusof
mesh_terms: D000818:Animals; D004967:Estrogens / Q000378:metabolism; D030762:Estrous Cycle / Q000502:physiology*; D005260:Female; D007719:Knee Joint / Q000378:metabolism*; D017847:Patellar Ligament / Q000378:metabolism*; D011374:Progesterone / Q000378:metabolism; D020033:Protein Isoforms; D016059:Range of Motion, Articular / Q000502:physiology*; D051381:Rats; D011921:Rats, Inbred WKY; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D018000:Receptors, Peptide / Q000235:genetics / Q000378:metabolism*
chemical_list: D004967:Estrogens; D020033:Protein Isoforms; D043562:Receptors, G-Protein-Coupled; D018000:Receptors, Peptide; C504789:Rxfp1 protein, rat; C511608:Rxfp2 protein, rat; D011374:Progesterone