Expression of transient receptor channel proteins in human fundal myometrium in pregnancy.
OBJECTIVE
Cation channels comprised of transient receptor potential (TrpC) proteins may play a role in signal-regulated calcium entry and calcium homeostasis in myometrium. The objective of this study was to determine the relative abundance of specific TrpC mRNAs expressed in human myometrium and determine if TrpC mRNA and protein concentrations differ in fundal myometrium before and after the onset of labor.


METHODS
A quantitative real-time polymerase chain reaction (Q-RT-PCR) procedure was developed for determining the concentration of TrpC mRNA expression in immortalized and primary human myometrial cells and myometrial fundus tissues from patients before and after the onset of labor. The corresponding TrpC proteins were detected by Western blot analysis and immunohistochemistry.


RESULTS
hTrpC1, 3, 4, 5, 6, and 7 mRNAs were expressed in two lines of immortalized human myometrial cells and in primary human myocytes. In all of these cells, hTrpC1 and hTrpC4 mRNAs were the most abundant, followed by hTrpC6. A similar distribution was observed in fundal myometrium samples from patients before and after the onset of labor. hTrpC4 mRNA was significantly lower after the onset of labor; there were no significant changes in the concentrations of other TrpC mRNAs. Immunohistochemistry identified hTrpC1, 3, 4, and 6 proteins in myometrial smooth muscle cells. Western blot analysis of myometrial membranes demonstrated no statistically significant changes in hTrpC1, 3, 4, and 6 proteins between samples collected before and after the onset of labor.


CONCLUSIONS
We have demonstrated that hTrpC1 and hTrpC4 are the most abundant TrpC mRNAs in human myometrium, with TrpC6 being the next most abundant. There was no increase in TrpC mRNA or protein in fundal myometrium with the onset of labor. Nonetheless, these isoforms may play significant roles in signal regulated calcium entry in human myometrium.
Ku
Chun-Ying
CY
Department of Biomedical Sciences, Colorado State University, Fort Collins, Colorado 80523, USA. cku@lamar.colostate.edu
Babich
Lidiya
L
Word
R Ann
RA
Zhong
Miao
M
Ulloa
Aida
A
Monga
Manju
M
Sanborn
Barbara M
BM
D002118:Calcium / Q000378:metabolism*; D018929:Cell Culture Techniques; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D015151:Immunoblotting; D007743:Labor, Obstetric / Q000378:metabolism*; D009215:Myometrium / Q000378:metabolism*; D011247:Pregnancy; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D050052:TRPC Cation Channels / Q000096:biosynthesis* / Q000502:physiology; D000074287:TRPC6 Cation Channel
D020033:Protein Isoforms; D012333:RNA, Messenger; D050052:TRPC Cation Channels; C489571:TRPC4 ion channel; D000074287:TRPC6 Cation Channel; C117032:TRPC6 protein, human; C096351:transient receptor potential cation channel, subfamily C, member 1; D002118:Calcium