11 Jan

Regulation of Anion Secretion by Prostaglandin E2: RESULTS(1)

RESULTS(1)

lsc Responses to PGE2

The mouse endometrial culture exhibited a mean basal Isc (Ib) °f 6.2 ± 0.2 (xAcm 2 (n = 145), a mean transepithelial resistance (Rj) of 580 ± 20 Hem2 (n = 145), and a mean transepithelial potential (Vx) of 4.1 ± 0.2 mV (n = 145). The cultured mouse endometrial epithelium responded to apical as well as basolateral addition of PGE2 with a sustained increase in the Isc (Fig. 1, A and B). The ISc response to apical addition of 5 |xM PGE2 reached an averaged peak value of 3.3 ± 0.3 [xA/cm2 (n = 23), while the peak value of the Isc response to basolateral addition of 1 ц,М PGE2 was 5.4 ± 0.4 (лА/cm2 (n = 24). Both responses usually took about 7 min to reach the peak, and the responses lasted for at least 30 min. The value of the peak response was used for analysis throughout the study.

As shown in Figure 2, PGE2 stimulated Isc in a concentration-dependent manner, with a value of half-maximum effective concentration (EC50) at about 200 and 4 nM for apical and basolateral addition of PGE2, respectively. asthma inhalers

Anion Dependence of the PGE2-Stimulated lsc

Ion substitution experiments were conducted to study the ion species involved in mediating the PGE2-stimulated ISc response (Fig. 3). When Cl in the bathing solutions was replaced by gluconate, the PGE2-stimulated ISc was reduced by 66.7 ± 1.5% (n = 4) and 57.5 ± 2.2% (n = 4) for apical and basolateral addition of PGE2, respectively. In HC03 -free solution, the PGE2-stimulated Isc was reduced by 60.4 ± 2.0% (n = 3) for apical addition of PGE2, but a 22.7 ± 7.0% (n = 4) reduction was observed for the basolateral response, suggesting differential dependence of these responses on HCO3. When both external Cl and HCO3 ions were replaced, 85% of the PGE2-induced Isc response of either membrane was reduced, indicating a predominant anion dependence of the PGE2-stimulated ISc response.
Fig1Regulation of anion secretion
FIG. 1. Effect of PGE2 on the lsc. A) Current recording with arrow marking the time at which apical (ap.) PGE2 was added (representative of 23 experiments; lb: 7.5 ixAcrrr2; RT: 450 Пет2). В) Current response to ba-solateral (Ы.) PGE2 (representative of 24 experiments; lb: 4.6 ц-Асггг2; RT: 900 Пет2). Experiments were performed in normal K-H solution. The horizontal line represents zero lsc. The transient current pulses resulted from an intermittently applied voltage of 0.1 mV, from which transepithe-lial resistance could be calculated.

Fig2Regulation of anion secretion
FIG. 2. Concentration-dependent response curves of apically and ba-solaterally applied PGE2. Change in lsc is plotted against PGE2 concentrations. Data for each point were obtained from at least 3 independent experiments. Values are mean ± SE. The £C50 for apical and basolateral addition of PGE2 is about 200 nM and 4 nM, respectively.

Fig3Regulation of anion secretion
FIG. 3. Effect of ion substitution on the PGE2-induced lsc. Mean lsc responses to apical (A) or basolateral addition of PGE2 (B) obtained in normal K-H, Ch-free, HC03~-free, and Cl- and HC03~-free bathing solutions are plotted, means ± SE (n > 3). Single and double asterisks indicate p < 0.05 and p < 0.01, respectively, when compared to corresponding experimental group with PGE2 stimulation to the other side of the membrane.

Categories: Prostaglandin
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