Relaxin: Target Tissues and Effects on Uterine Contraction in Vivo and in Vitro in the Rat

Possible target tissues for relaxin in estrogen-primed ovariectomized rats were identified by determing (1) the tissue distribution of injected ('125)I-labeled relaxin (('125)I-relaxin) in vivo and (2) the changes in cyclic AMP (cAMP) levels in several tissues following incubation with relaxin in vitro. Porcine relaxin was radioiodinated with ('125)I-labeled Bolton-Hunter reagent. Relaxin retained its biological activity following modification with unlabeled Bolton-Hunter reagent (N-succinimidyl 3-(4-hydroxyphenyl) propionate). Of the tissues examined, thyroid, kidney, liver, spleen, lung and uterus (horns and cervix) had higher concentrations of radioactivity than blood during the first 4 h following the injection of 5 (mu)Ci (approximately 16 ng) of ('125)I-labeled relaxin. Only with the uterus could the higher levels of radioactivity be significantly displaced by the simultaneous administration of 15,000 ng of unlabeled relaxin (P < 0.05). Samples of uterine horns and cervix, liver, kidney, spleen, adrenal, diaphragm, lung, ileum, bladder, ureter and arterial vascular wall were incubated with Krebs-Ringer bicarbonate buffer (pH 7.4, 37C, gas phase 95%O(,2)-5%CO(,2), containing 5.5 mM glucose and 5 mM theophylline). After 15 min of incubation with 4 (mu)g/ml porcine relaxin, only the uterine horns and cervix showed significant increases in cAMP levels over controls (P < 0.001) as measured by radioimmunoassay. The increases in cAMP levels within the uterine horns were time and hormone-dose dependent. It appears that the uterine horns and cervix are target tissues for relaxin in the estrogen-primed ovariectomized rat. Relaxin may exert its biological effects, at least in part, through cAMP.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physiology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2014

Author dc:creator

• Cheah, Swee Hung

• Biology, Animal Physiology

Language dc:language

eng

Identifier

(UMI)AAI8114399

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/68308