Objective: To assess the effect of insulin on the Na+/ K+-ATPase expression and activity in human peritoneal mesothelial cells (HPMC). Methods: HPMC were isolated from the omental tissue of non-uremic patients, grown to confluence and rendered quiescent by serum deprivation for 24 hours. The activity of Na+/K+-ATPase was determined by measuring the ouabain-sensitive 86Rb uptake. To assess whether the effect of insulin was related to changes in [Na+](i) the sodium influx was measured with 22Na and the activity of Na+/K+-ATPase was assessed in the presence of amiloride. Expression of Na+/K+-ATPaseα1, α2 and β1-subunit mRNAs was determined by RT/PCR. Results: Exposure of HPMC to insulin resulted in a time- and dose-dependent increase in the Na+/K+-ATPase activity. After 60 minutes the ouabain-sensitive 86Rb uptake (cpm/104 cells) was increased from 6650 ± 796 in control cells to 9763 ± 1212 in HPMC exposed to 100 mU/mL insulin (1.5-fold increase; n = 4, P < 0.05). In addition, incubation of HPMC with 100 mU/mL insulin resulted in a time-dependent increase in the 22Na influx. pre-exposure of HPMC to 1 mM amiloride reduced the activity of Na+/K+-ATPase but did not block the stimulatory effect of insulin. RT/PCR analysis revealed that HPMC constitutively expressed α1- and β1-subunit mRNAs while the α2-subunit mRNA was barely detectable. Exposure of HPMC to insulin for up to 24 hours was not associated with any changes in the expression of either α1, α2 or β1-subunit. Conclusion: Insulin stimulates the Na+/K+-ATPase activity in HPMC in a time- and dose-dependent manner. This effect appears to mediated by an increase in [Na+](i) and is not related to alterations in Na+/K+-ATPase subunit mRNAs expression.
- Mesothelial cells
ASJC Scopus subject areas