Humoral factors of the spleen in the regulation of the calcium content in blood plasma of rats]

Introduction of protein-free peptides-enriched spleen extract increases the calcium content in blood plasma of rats. After the effect of stress factor (long swimming) it falls. The value of the index under study increases in the splenectomized rats and remains unchanged after stress and introduction of the spleen factors. The most pronounced increase of the calcium concentration is observed in the case of experimental hypersplenism induced by methylcellulose introduction. The calcium-regulating effects of introduction of the enriched protein-free spleen extract and pharmacopoeial splenin preparation are compared. It is supposed that spleen contains two humoral factors of different chemical nature which are able to influence somewhat differently the calcium content in blood plasma.     

Role of calcium in volume regulation by dog red blood cells

Dog red blood cells (RBC) are shown to regulate their volume in anisosmotic media. Extrusion of water from osmotically swollen cells requires external calcium and is associated with net outward sodium movement. Accumulation of water by osmotically shrunken cells is not calcium dependent and is associated with net sodium uptake. Net movements of calcium are influenced by several variables including cell volume, pH, medium sodium concentration, and cellular sodium concentration. Osmotic swelling of cells increases calcium permeability, and this effect is diminished at acid pH. Net calcium flux in either direction between cells and medium is facilitated when the sodium concentrations is low in the compartment from which calcium moves and/or high in the compartment to which calcium moves. The hypothesis is advanced that energy for active sodium extrusion in dog RBC comes from passive, inward flow of calcium through a countertransport mechanism.     

Acute emotional stress and cyclic nucleotide content of the heart and blood plasma

The relationships between the changes in arterial pressure and the content of cyclic nucleotides in the heart and blood plasma were studied on rabbits exposed to acute emotional stress. During 3 hours of the stress program, there were changes in arterial pressure, namely an elevation within the first hour followed by a progressive fall during subsequent 2 hours and death of the animals. The content of cAMP in the heart rose to a greater degree than that of cGMP. The content of cAMP in the blood plasma considerably increased, while the level of cGMP remained unchanged. The data obtained attest to the predominance of activation of adrenergic structures over activation of cholinergic structures.     

Role of endoplasmic reticulum calcium content in prostate cancer cell growth regulation by IGF and TNFalpha

Variations in calcium concentration within the endoplasmic reticulum ([Ca(2+)](ER)) may play a role in cell growth. This study evaluates the regulation of calcium pools by growth modulators of prostate cancer (PC) cells, the insulin growth factor (IGF), and the tumor necrosis growth factor-alpha (TNFalpha) as well as evaluating the possible role of [Ca(2+)](ER) variations as signals for growth modulation. We show that IGF (5 ng/ml), which increases cell growth, induces an increase in [Ca(2+)](ER) whereas TNFalpha (1 ng/ml) which reduces cell proliferation and induces apoptosis, reduces [Ca(2+)](ER). IGF-induced [Ca(2+)](ER) increase is correlated to an overexpression of the sarcoendoplasmic calcium-ATPase 2B (SERCA2b), whereas TNFalpha-induced [Ca(2+)](ER) decrease is associated to a reduction in SERCA2b expression. Pretreatment with epidermal growth factors (EGF) or IGF does not prevent TNFalpha from affecting the induction of apoptosis, [Ca(2+)](ER) reduction and SERCA2b downregulation. Reduction in [Ca(2+)](ER) induced by thapsigargin (TG) (from 1 pM to 1 microM, 48 h) reduces LNCaP growth in a dose dependent manner and induces apoptosis when cells are treated with 1 microM TG. We also show that a transient TG application (1 pM, 1 nM, 1 microM 15 min) is insufficient to induce a long lasting decrease in [Ca(2+)](ER), since [Ca(2+)](ER) remains identical to the control for 48 h following TG application. These treatments (1 pM and 1 nM, 15 min) do not modify cell growth. However, TG (1 microM, 15 min) induces apoptosis. We thus identify [Ca(2+)](ER) and SERCA2b as a central targets for causing LNCaP PC cell life or death induced by growth modulators. Furthermore our results indicate that calcium pool contents can regulate cell growth.     

Role of spleen in ANF-induced reduction in plasma volume.

Atrial natriuretic factor (ANF) causes an increase in hematocrit that cannot be accounted for by urinary losses. The mechanism behind this phenomenon was studied in intact and splenectomized rats. Rat ANF 99-126 was infused i.v. for 30 min into conscious rats at rates of 0 (saline control), 0.05, or 0.1 microgram/min. Plasma volume was then determined by dilution of the dye, Evan's Blue. In one group of rats, red cell volume was determined using 51Cr-labelled erythrocytes. ANF infusion was continued uninterrupted throughout the experiments. In the intact rats, ANF (0.10 microgram/min) caused hematocrit to increase from 38.9 +/- 0.5 to 41.2 +/- 0.4% (p < 0.005). Splenectomy so attenuated this response to ANF that it failed to reach significance. Similarly, ANF (0.10 microgram/min) caused plasma volume to fall from 5.1 +/- 0.1 to 4.5 +/- 0.1 mL/100 g body wt. (p < 0.005) in the intact rats, but did not affect plasma volume in the splenectomized rats. As a result, blood volume was significantly reduced by ANF in the intact rats, but remained unchanged in the splenectomized rats. Red cell volume did not change in response to infusion of ANF, nor did ANF affect the rate of clearance of Evan's Blue out of the plasma. It is concluded that the spleen is an important site of movement of protein-poor fluid out of the vasculature, and that this exchange is influenced by ANF.     

Effect of fenazepam on the ACTH content of the blood plasma in inbred mice under stress exposure

The influence of phenazepam on plasma ACTH level before and after exposure to stress in the "open field" test was investigated in C57BL/6, BALB/c and F1(C57BL/6 X BALB/c) mice. The differences in the dose-dependent drug effect on the hormone level between strains were studied. A correlation between ACTH level and a characteristic animal behaviour has been established for different strains.