Pentose phosphate pathway coordinates multiple redox-controlled relaxing mechanisms in bovine coronary arteries

Pentose phosphate pathway (PPP) inhibitors, 6-aminonicotinamide (6-AN) and epiandrosterone (Epi), were employed to examine whether changes in NADP(H) redox regulates contractile force in endothelium-removed bovine coronary arteries (BCAs). 6-AN (0.01-5 mM) or Epi (1-500 microM) elicited dose-dependent relaxation in BCAs contracted with 30 mM KCl, 0.1 microM U-44619, and endothelin-1 but not with phorbol 12,13-dibutyrate, a protein kinase C activator that causes Ca2+-independent contraction. Relaxation to PPP inhibition was associated with oxidation of NADPH and glutathione (GSH). Relaxation to 6-AN was not mediated by H2O2, because it was not altered by hypoxia or the peroxide scavenger ebselen (100 microM). The thiol reductant DTT (3 mM) attenuated the relaxation to 6-AN and Epi by 30-40%. Inhibition of glycolysis or mitochondrial electron transport did not elicit relaxation in BCAs contracted with 30 mM KCl, suggesting these pathways may not be involved in relaxation elicited by PPP inhibition. High doses of K+ channel blockers [e.g., TEA (10 mM) and 4-aminopyridine (10 mM)] only partially inhibited the relaxation to 6-AN. On the basis of changes in the fura-2 fluorescence ratio, 6-AN and Epi appeared to markedly reduce intracellular Ca2+. Thus PPP inhibition oxidizes NADPH and GSH and appears to activate a novel coordination of redox-controlled relaxing mechanisms in BCAs mediated primarily through decreasing intracellular Ca2+.     

Inter‐annual site fidelity and breeding origins of Gray‐cheeked Thrushes in white sand forests of the Peruvian Amazon

White sand terra firme forests are unusual ecosystems scattered across Amazonia, covering just 3% of the basin. These forests differ from surrounding forests in their scleromorphic vegetation, low nutrient content, and propensity to harbor endemics. We report the capture of 62 Gray‐cheeked Thrushes (Catharus minimus) during a study of the understory avifauna of Amazonian white sand forests near Iquitos, Peru, conducted from 20 June to 8 December 2010–2012. We captured and banded Gray‐cheeked Thrushes in white sand (N = 57) and adjacent weathered clay (N = 5) terra firme forests. Sampling for three consecutive days at 19 different sites each year, the inter‐annual site fidelity rate of Gray‐cheeked Thrushes was 4.8% (N = 3). One bird banded in 2010 was recaptured in 2012. Of the 62 birds, 19.3% (N = 12) were recaptured on subsequent days. All recaptures were in white sand forests. The 19.3% recapture rate of Gray‐cheeked Thrushes from sites re‐sampled no more than 2 d in a given year suggests the presence of settled and perhaps territorial birds. Using rectrices from 12 Gray‐cheeked Thrushes, stable‐hydrogen isotope analyses (δ²H) suggest that the geographic breeding or natal origin of all sampled birds was likely northwestern North America. Our results suggest that Gray‐cheeked Thrushes exhibit site fidelity and may concentrate in white sand forests—an uncommon and scattered ecosystem type in western Amazonia. However, annual tracking of individual Gray‐cheeked Thrushes is needed to fully assess regional patterns of settlement and movement, and the connectivity between breeding and wintering areas.