[Solitary Peripheral Pulmonary Squamous Cell Papilloma;Diagnostic Significance of 18F-fluorodeoxyglucose Positron Emission Tomography Findings].

The patient was a 79-year-old woman who had received enucleation of right pulmonary papilloma 7 years earlier. She experienced bloody sputum and was therefore referred to our hospital. Chest computed tomography revealed a mass shadow(21 mm) in the right upper lobe (S2). By bronchoscopy, there was no bulging lesion in the visible range. SCC and CEA increased to 6.4 ng/ml and 6.42 ng/ml, respectively. Whole-body 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) showed increased FDG uptake in the region of the right-lung mass shadow (maximum standardized uptake value 12.95). Since malignancy could not be ruled out, a wedge resection was performed. The post-operative histopathologic diagnosis was squamous cell papilloma. Our literature review showed 12 out of 14 cases with solitary papilloma of the peripheral lung to have increased FDG uptake. Ki-67 positive cells were confirmed in the basal layers of the epithelium, and active cell proliferation of the papilloma is likely to be a cause of increased FDG uptake.

HCO(-3)-dependent pHi recovery and overacidification induced by NH+4 pulse in rat lung alveolar type II cells: HCO(-3)-dependent NH3 excretion from lungs?

Intracellular pH (pHi) after the NH+4 pulse addition and its removal were measured in isolated alveolar type II cells (ATII cells) using BCECF fluorescence. In the absence of HCO(-3), the NH+4 pulse addition increased pHi (alkali jump) and its removal decreased pH(i) (acid jump) to the control level (no overacidification). This pHi change was induced by reaction 1 (NH3 + H+ <--> NH+4). However, in the presence of HCO(-3), the NH+4 pulse removal decreased pHi (acid jump) with overacidification. The extent of overacidification was decreased by acetazolamide (a carbonic anhydrase inhibitor), bumetanide (an inhibitor of Na+/K+/2Cl(-) cotransporter [NKCC]), and NPPB (an inhibitor of Cl(-) channel). The NH+4 pulse addition led to the accumulation of NH+4 in ATII cells via reaction 1 and NKCC, and the NH+4 pulse removal induced reaction 2 (NH+4 + HCO(-3) --> NH3 + H+ HCO(-3)) in addition to the reversal of reaction 1. Thus, NH+4 that entered via NKCC reacts with HCO(-3) (reaction 2) to produce H+, which induces overacidification in the acid jump. After the overacidification, the pH(i) recovery consisted of a rapid recovery (first phase) followed by a slow recovery (second phase). The first phase was inhibited by NPPB, glybenclamide, amiloride, and an Na+-free solution, and the second phase was inhibited by DIDS, MIA, and an Na+-free solution. Both phases were accelerated by a high extracellular HCO(-3) concentration. These observations indicate that the first phase was induced by HCO(-3) entry via Cl(-) channels coupled with Na+ channels activities, and that the second phase was induced by H+ extrusion via Na+/H+ exchanger and by HCO(-3) entry via HCO(-3) cotransporter. Thus, in ATII cells, HCO(-3) entry via Cl(-) channels is essential for recovering pHi after overacidification during the acid jump and for removing NH+4 that entered via NKCC from ATII cells, suggesting HCO(-3)-dependent NH3 excretion from lungs.

Cell shrinkage evoked by Ca2+-free solution in rat alveolar type II cells: Ca2+ regulation of Na+-H+ exchange.

The effects of intracellular Ca2+ concentration, [Ca2+]i, on the volume of rat alveolar type II cells (AT-II cells) were examined. Perfusion with a Ca2+-free solution induced shrinkage of the AT-II cell volume in the absence or presence of amiloride (1 microm, an inhibitor of Na+ channels); however, it did not in the presence of 5-(N-methyl-N-isobutyl)-amiloride (MIA, an inhibitor of Na+-H+ exchange). MIA decreased the volume of AT-II cells. Inhibitors of Cl(-)-HCO3- exchange, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS) also decreased the volume of AT-II cells. This indicates that the cell shrinkage induced by a Ca2+-free solution is caused by a decrease in NaCl influx via Na+-H+ exchange and Cl(-)-HCO3- exchange. Addition of ionomycin (1 microm), in contrast, induced cell swelling when AT-II cells were pretreated with quinine and amiloride. This swelling of the AT-II cells is not detected in the presence of MIA. Intracellular pH (pHi) measurements demonstrated that the Ca2+-free solution or MIA decreases pHi, and that ionomycin increases it. Ionomycin stimulated the pHi recovery after an acid loading (NH4+ pulse method), which was not noted in MIA-treated AT-II cells. Ionomycin increased [Ca2+]i in fura-2-loaded AT-II cells. In conclusion, the Na+-H+ exchange activities of AT-II cells, which maintain the volume and pHi, are regulated by [Ca2+]i.