Physiological effect of protein kinase C on ENaC-mediated lung liquid regulation in the adult rat lung

Abstract

The aim of this work was to determine whether PKC activation is involved in the physiological regulation of LL volume in a whole lung preparation. Rat lungs were perfused with a modified Ringer solution, and the lumen was filled with the same solution without glucose. LL volume was measured during a control period and after modulating drugs were administered, and net LL transepithelial movement (Jv) was calculated. When the PKC activator PMA (10 Ϫ5 M) and the Ca 2ϩ ionophore ionomycin (10 Ϫ6 M) were instilled into the lung together, Jv was significantly reduced (P ϭ 0.03). This reduction was blocked by the PKC inhibitor chelerythrine chloride (10 Ϫ6 M; P ϭ 0.56) and by a second PKC inhibitor GF109203X (10 Ϫ5 M; P ϭ 0.98). When PMA and ionomycin were added with the ␤-adrenergic agonist terbutaline, the terbutaline-induced increase in Jv was abolished. Addition of PMA and ionomycin with the epithelial Na ϩ channel (ENaC) blocker amiloride had no additional inhibitory effect. Together, these results suggest that PKC is likely to be involved in LL absorption, and the ability of PMA/ionomycin to block the terbutaline-induced increase in Jv suggests that the downstream target of PKC is ENaC.calcium-dependent protein kinase C; ionomycin; phorbol 12-myristate 13-acetate TIGHT CONTROL OF LUMINAL lung liquid (LL) volume is essential for normal pulmonary function. An excess or deficiency of LL in the airway and the alveoli leads to pathology, so mechanisms to control LL volume are critical. In the airway, there is a dynamic balance between secretion and absorption of liquid (30), and some of the cellular mechanisms involved have been shown to be present in alveolar cells (13). Cl Ϫ transport seems to underlie liquid secretion into the lumen, while Na ϩ transport has been shown to be essential for liquid absorption. The Na ϩ absorptive mechanisms have received more attention than the Cl Ϫ secretory mechanisms, and the airway epithelium has been better studied than the alveolar barrier, although the latter contributes by far more surface area (by a ratio of Ն500:1, if not 850:1) (18).The principal channel responsible for Na ϩ absorption is the epithelial Na ϩ channel (ENaC), which has been the focus of much research. In the perinatal period, activation of lung ENaC is very sensitive to epinephrine, which causes a dramatic reversal of net transepithelial liquid flow (J v ), thereby facilitating the change at birth from a prenatal secreting phenotype to an absorption phenotype (9, 17). Hummler et al. (15) demonstrated that ␣-ENaC-deficient (Ϫ/Ϫ) mice were unable to survive beyond 40 h after birth. These animals died from acute respiratory failure with liquid-filled lungs, providing conclusive evidence that ENaC is vital for the liquid absorption at birth. During postnatal life, there is a dynamic balance between the secretory and absorptive processes. Although liquid absorption predominates in the liquid-filled lung, a secretory mechanism persists and can be demonstrated to be present under certain circumstances (25). The me...

Non-Genomic Estrogen Regulation of Ion Transport and Airway Surface Liquid Dynamics in Cystic Fibrosis Bronchial Epithelium

“…For example, estrogen produced a 50% inhibition of 22 Na + uptake in pig kidney epithelial LLC-PK1 cells after PMA (PKC activator) treatment [43]. In the alveoli, it has been shown that PKC is involved in ENaC-mediated lung liquid regulation [44]. However, to our knowledge, no report has shown that the PKCδ isoform could regulate fluid absorption through the bronchial epithelia.…”

Hydrogen sulfide decreases β-adrenergic agonist-stimulated lung liquid clearance by inhibiting ENaC-mediated transepithelial sodium absorption

“…The in situ perfused rat preparation used in these experiments has been described previously (75,89). All animal experiments were approved by independent committees.…”

La membrana alveolo-capilar

“…Se ha descrito que los canales de sodio son elementos fundamentales en la regulación del edema, y que una función correcta de los mismos podría resolver este evento de forma vectorial (102)(103)(104)(105)(106). Aparentemente, se requiere la subunidad de Na-K ATPasa para la polarización celular y formación de uniones intercelulares, esenciales en la estabilización de la barrera (107)(108)(109)(110).…”