Physiological concentrations of atrial natriuretic factor stimulate human erythroid progenitors in vitro

Natriuretic peptides in hormonal regulation of hypoxia responses

The possibility that natriuretic peptides' effects are important in hypoxia responses of vertebrates is reviewed. Both the transcription and release of natriuretic peptides are affected by oxygen tension. Furthermore, many of the effects observed in hypoxia, such as diuresis and a reduction of plasma volume, are also caused by treatment of the animal with natriuretic peptides. Also, several clinical observations about changes in natriuretic peptide levels in, e.g., sleep apnea and cyanotic congenital heart disease, are consistent with the idea that hypoxia is involved in the etiology of conditions, in which natriuretic peptide levels increase. Virtually all published information on the relationship between oxygen and natriuretic peptides is based on human studies. Because hypoxic conditions are more common in aquatic than terrestrial environments, future studies about the possible role of natriuretic peptides in hypoxia, as well as the role of hypoxia in the evolution of natriuretic peptides, including the different subtypes, should increasingly involve also aquatic organisms.

Atrial natriuretic peptide: direct effects on human red blood cell dynamics

The ability to deform is an important feature of red blood cells (RBCs) for performing their function of oxygen delivery. Little is known about the hormonal regulation of RBC deformability. Here we report that human atrial natriuretic peptide (ANP) acts directly on human RBCs leading to the elevation of local bending fluctuations of the cell membrane. These changes are accompanied by an increase in the filterability of RBCs. These ANP effects were mimicked by cyclic GMP analogues, suggesting modulation of local membrane bending fluctuations and RBC filterability via a cyclic GMP-dependent pathway. The effect of ANP on the mechanical properties of RBCs suggests that ANP may increase the passage red blood cells through capillaries resulting in an improved oxygen delivery to the tissues.

Evidence that atriopeptin is not a physiological regulator of sodium excretion

Although much experimental evidence is consistent with the concept that atrial natriuretic factor (atriopeptin) is an important physiological regulator of renal sodium excretion, this hypothesis remains unproven. Indeed, a rapidly expanding collection of experimental data appears to be more compatible with the opposite conclusion, namely that circulating atriopeptin exerts only a trivial effect on renal sodium excretion during normal day-to-day living conditions. In this review, the substantial evidence demonstrating that elevations of plasma atriopeptin from threefold to 13-fold produce only a slowly developing and relatively modest natriuresis is reassessed in light of recently published data indicating that the acute intake of food (the pathway by which essentially all sodium enters the body under normal living conditions) does not increase circulating atriopeptin. These considerations imply that atriopeptin does not contribute to the process that elicits a postprandial natriuresis, a process that presumably is of primary importance in the physiological regulation of sodium balance. In addition, consideration is given to a number of common physiological, experimental, and pathophysiological conditions in which circulating atriopeptin does not correlate with renal sodium excretion. This lack of correlation implies that atriopeptin is not an important regulator of sodium excretion in these situations.

Purification of erythropoiesis-stimulating activity (ESA) from one Actinomycetes strain

An Actinomycetes strain was found to produce a protein which stimulated the growth of murine erythroid progenitors in vitro. The protein was purified to homogeneity and was named Erythropoiesis-Stimulating Activity (ESA). ESA was an acidic glycoprotein with a molecular weight around 80,000. When mouse bone marrow cells were cultured in methylcellulose medium containing physiological concentrations of erythropoietin (0.048 units/ml), addition of ESA stimulated the growth of colony forming unit-erythroid (CFU-E) up to three-fold a in dose dependent manner. ESA was not active on the other hematopoietic progenitors.