Cleaved prolactin increases activity of amiloride‐sensitive sodium channels in mouse collecting duct principal cells (893.3)

Abstract

In the renal collecting duct, sodium reabsorption through the epithelial sodium channel (ENaC) creates an osmotic driving force for water reabsorption resulting in increased blood volume and pressure. Investigators have previously shown that prolactin (PRL) stimulated ENaC activity in bullfrog skin cells. However, studies in mammalian systems show no effect of PRL on ENaC function. PRL is present in two forms: a 23kDa full length form (PRL) and a 14‐16kDa cleaved form (PRL‐C). We hypothesized that these two PRL molecules may exert different effects on ENaC activity. To investigate this hypothesis, we used a cell culture model of principal cells from the cortical collecting duct (mpkCCD) which express ENaC subunits and exhibit amiloride‐sensitive current. We measured transepithelial voltage and resistance across cell monolayers before and after basolateral treatment with vehicle (water) or 1‐2 ug/mL of PRL or PRL‐C and calculated transepithelial current using Ohm’s law. We found that PRL produced only a small, variable effect on ENaC activity in mpkCCD cells. However, PRL‐C approximately doubled the amiloride‐sensitive current in these cells within 24 hrs. Compared to kidney lysates, mpkCCD cells exhibit a low abundance of the PRL receptor which may explain the need for large PRL concentrations in these cells. Our results indicate that cleaved PRL stimulates ENaC activity in mpkCCD cells. In future studies, we will examine the effect of PRL and PRL‐C on single channel properties of ENaC in isolated collecting ducts and the effect of these hormones on blood pressure in vivo.Grant Funding Source: Supported by NIH K12GM000680 and T32HL076118