Expression and Distribution of Na, K-ATPase Isoforms in the Human Uterus

Na, K-ATPase activity relies on the composition of its catalytic alpha, beta, and FXYD constituents, all of which are expressed as multiple isoforms (4 alpha, 4 beta, and 7 FXYD). We used reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemistry to study Na, K-ATPase expression in uterine samples from nonlaboring elective and laboring emergency caesarean sections (CSs). Transcripts of alpha 1 to 3, beta 1 to 3, and FXYD1 isoforms were detected in all samples, but FXYD2 was only present in hysterectomy samples. Abundant immunoreactivity of alpha 1 and moderate alpha 2 was localized in myometrial smooth muscle and secretory glands of all groups. Smooth muscle and gland epithelia showed diffuse cytoplasmic alpha 3 immunoreactivity. beta isoforms were detected in all groups but beta 3 showed much denser immunoreactivity in myometrial samples taken from women in labor. In pregnancy, there was a switch in isoform expression, resulting in increased beta 3 and decreased FXYD2 at the protein and messenger RNA (mRNA) levels. Na, K-ATPase isoform alterations may modulate uterine contractility during labor.