Abstract
BackgroundThe present study demonstrates the expression of intermedin (IMD) and its receptor components in the uterus of the female rat during the estrous cycle and its effect on uterine contraction.MethodsThe gene expression level of intermedin and its receptor components and the peptide level of intermedin were studied by real-time RT-PCR and enzyme immunoassay (EIA) respectively. The separation of precursor and mature IMD was studied by gel filtration chromatography and EIA. The localization of IMD in the uterus was investigated by immunohistochemistry. The effect of IMD on in vitro uterine contraction was studied by organ bath technique.ResultsUterine mRNAs of Imd and its receptor components and IMD levels displayed cyclic changes across the estrous cycle. Imd mRNA level was the highest at proestrus while the IMD level was the highest at diestrus. IMD was found in the luminal and glandular epithelia and IMD treatment significantly reduced the amplitude and frequency of uterine contraction but not the basal tone. Both calcitonin gene-related peptide (CGRP) receptor antagonist hCGRP8-37 and adrenomedullin (ADM) receptor antagonist hADM22-52 partially abolished the inhibitory effect of IMD on uterine contraction while the specific IMD receptor antagonist hIMD17-47 completely blocked the actions. The enzyme inhibitors of NO (L-NAME) and PI3K (Wortmannin) pathways diminished the IMD effects on uterine contraction while the cAMP/PKA blocker, KT5720, had no effect, indicating an involvement of NO and PI3K/Akt but not PKA.ConclusionsIMD and the gene expression of its receptor components are differentially regulated in the uterus during the estrous cycle and IMD inhibits uterine contraction by decreasing the amplitude and frequency.
Highlights
The present study demonstrates the expression of intermedin (IMD) and its receptor components in the uterus of the female rat during the estrous cycle and its effect on uterine contraction
As ADM is known to inhibit uterine contraction [25,26], we have investigated the changes of IMD gene expression and peptide levels in the uterus during the estrous cycle and its effect on spontaneous uterine contraction to understand the possible roles of IMD in the uterus
IMD immunoreactivity and mRNA level of Imd The levels of IMD and Imd mRNA in the uterus of cycling rats were estimated by IMD enzyme immunoassay (EIA) and real-time RT
Summary
The present study demonstrates the expression of intermedin (IMD) and its receptor components in the uterus of the female rat during the estrous cycle and its effect on uterine contraction. IMD has several functions similar to those of ADM. Both IMD and ADM are potent vasodilators [2,8,9] and are anorexogenic [2,4,10]. Both suppress stomach emptying [2,11,12] and increase circulating prolactin levels [2,13,14]. IMD has its own effects not shared by ADM [15,16,17,18,19,20,21].
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