Fig. 9.
Effects of the P2Y1 receptor antagonist MRS2500 on MRS2365-, thio-UTP-, or ATP-induced Isc in mIMCD-K2 cells. A: superimposed representative traces of Isc responses to the addition of the P2Y1 agonist MRS2365 or the P2Y2 agonist thio-UTP following treatment with control (solid trace) or with 10−6 M P2Y1 receptor antagonist MRS2500 (dashed trace) added to both sides of cell sheets. Am, 10−5 M amiloride; MRS2500, 10−6 M MRS2500; MRS(a) and MRS(b) indicate addition of 10−6 M P2Y1 agonist MRS2365 to the apical and basal sides, respectively. UTP(b) and UTP(a) indicate the addition of 10−6 M P2Y2 agonist thio-UTP to the basal and apical sides, respectively. B: average Isc values in the transient response to basal addition of either MRS2365 (ΔIsc) or thio-UTP in control cells (open bars) or in cells pretreated with MRS2500 (closed bars). Values are means ± SE (n = 9 filters). *Value significantly different from control value. C: representative trace of Isc showing that pretreatment of both sides of cell sheets with the P2Y1 antagonist MRS2500 (10−6 M) blocked the stimulatory effects of the P2Y1 agonist MRS2365 (10−6 M) added to the basal side of cell sheets [MRS(b)]. MRS(a) indicates MRS2365 (10−6 M) added to the apical side. Pretreatment of MRS2500 did not affect the stimulatory effects of ATP on Isc when added to either the basal [ATP(b)] or apical [ATP(a)] sides of cell sheets (n = 6 filters).