Lead ions but not other metallic ions increase resistance to hypotonic lysis in prenatal hemopoiesis red blood cells

Metals known to have toxic effects on exposed individuals (Aluminum (Al), Cadmium (Cd), Zinc (Zn) and lead (Pb)) were selected. Umbilical cord erythrocytes from normal newborns were incubated in isotonic media alone or with addition of Pb (20 microM), Cd, Zn or Al (concentration range: 20-250 microM). Red cells were then placed in media of diminishing tonicity, to measure cellular lysis and volume; the regression curves of percent lysis as a function of osmolarity were determined for each data set and the break points calculated. Resistance to lysis increased significantly in Pb treated cells whereas cells treated with the other metals did not differ from controls, even at concentrations ten times higher than that of Pb. Lead produced a reduction in cellular volume corrected by addition of quinidine (an inhibitor of potassium channels activation) to the cell suspension; on the other hand, quinidine did not modify the effect of lead on lysis sensitivity. These results suggest that the effect of lead on cell resistance to lysis might be mediated by changes in membrane structure. The other metals examined did not affect the variables studied.(AU)

Lead ions but not other metallic ions increase resistance to hypotonic lysis in prenatal hemopoiesis red blood cells

Metals known to have toxic effects on exposed individuals (Aluminum (Al), Cadmium (Cd), Zinc (Zn) and lead (Pb)) were selected. Umbilical cord erythrocytes from normal newborns were incubated in isotonic media alone or with addition of Pb (20 microM), Cd, Zn or Al (concentration range: 20-250 microM). Red cells were then placed in media of diminishing tonicity, to measure cellular lysis and volume; the regression curves of percent lysis as a function of osmolarity were determined for each data set and the break points calculated. Resistance to lysis increased significantly in Pb treated cells whereas cells treated with the other metals did not differ from controls, even at concentrations ten times higher than that of Pb. Lead produced a reduction in cellular volume corrected by addition of quinidine (an inhibitor of potassium channels activation) to the cell suspension; on the other hand, quinidine did not modify the effect of lead on lysis sensitivity. These results suggest that the effect of lead on cell resistance to lysis might be mediated by changes in membrane structure. The other metals examined did not affect the variables studied.

Lead ions but not other metallic ions increase resistance to hypotonic lysis in prenatal hemopoiesis red blood cells.

Metals known to have toxic effects on exposed individuals (Aluminum (Al), Cadmium (Cd), Zinc (Zn) and lead (Pb)) were selected. Umbilical cord erythrocytes from normal newborns were incubated in isotonic media alone or with addition of Pb (20 microM), Cd, Zn or Al (concentration range: 20-250 microM). Red cells were then placed in media of diminishing tonicity, to measure cellular lysis and volume; the regression curves of percent lysis as a function of osmolarity were determined for each data set and the break points calculated. Resistance to lysis increased significantly in Pb treated cells whereas cells treated with the other metals did not differ from controls, even at concentrations ten times higher than that of Pb. Lead produced a reduction in cellular volume corrected by addition of quinidine (an inhibitor of potassium channels activation) to the cell suspension; on the other hand, quinidine did not modify the effect of lead on lysis sensitivity. These results suggest that the effect of lead on cell resistance to lysis might be mediated by changes in membrane structure. The other metals examined did not affect the variables studied.

Lead ions but not other metallic ions increase resistance to hypotonic lysis in prenatal hemopoiesis red blood cells.

Metals known to have toxic effects on exposed individuals (Aluminum (Al), Cadmium (Cd), Zinc (Zn) and lead (Pb)) were selected. Umbilical cord erythrocytes from normal newborns were incubated in isotonic media alone or with addition of Pb (20 microM), Cd, Zn or Al (concentration range: 20-250 microM). Red cells were then placed in media of diminishing tonicity, to measure cellular lysis and volume; the regression curves of percent lysis as a function of osmolarity were determined for each data set and the break points calculated. Resistance to lysis increased significantly in Pb treated cells whereas cells treated with the other metals did not differ from controls, even at concentrations ten times higher than that of Pb. Lead produced a reduction in cellular volume corrected by addition of quinidine (an inhibitor of potassium channels activation) to the cell suspension; on the other hand, quinidine did not modify the effect of lead on lysis sensitivity. These results suggest that the effect of lead on cell resistance to lysis might be mediated by changes in membrane structure. The other metals examined did not affect the variables studied.

Neonatal red blood cells: amiloride-insensitive Na+-H+ transport isoform would express Na+-Li+ exchange.

Neonatal red cells (umbilical cord blood) were in vitro incubated in isotonic media (thiocyanate as predominant anion). This experimental condition was selected as it was known that this chaotropic anion induced activation of Na+-H+ exchange. The transport amiloride-sensitive mechanism, that decreased the acidic intracellular pH change occurring in this medium, would correspond to Na+-H+ exchange (NHE1 isoform). However, the Na+-Li+ exchange, also determined in the cells in the above-mentioned medium was not affected by amiloride. The present data suggest that an amiloride insensitive Na+-H+ exchange isoform would express Na+-Li+ countertransport in these cells.

Lead effects on structural and functional cellular parameters in human red cells from a prenatal hematopoiesis stage.

An attenuation (or reversion) of the prolytic effect of lead on neonatal red cells is observed in iso- or hypotonic low ionic strength media. This effect correlates neither with concomitant activation of K+ (Ca2+ or Pb2+) channels nor with volume reduction. Neonatal erythrocytes were used in this study owing to their greater cellular density, as compared with adult red cells, for the above mentioned channels. The attenuation-reversion effect would be mediated through lead interactions with the cytoskeleton, a structure that is the limiting factor for red cell lysis in low ionic strength media.

The homogeneous effect of calcium ionophore A23187 on potassium loss in human foetal red cell populations.

A "pulse like" increase of cytoplasmic calcium concentration, which is proportional to ionophore concentration, is induced in red cells by exposure to A23187. Different Ca2+ levels are attained depending on cellular calcium buffering power and/or primary active calcium transport activation. We examined the effect of A23187 concentration of potassium loss in neonatal (nRC) as well as in adult red cells (aRC). The increase in ionophore concentration produced an "all- or -none" recruitment in adult cells and a "gradual" one in neonatal red cells. The "gradual" response observed in nRC would suggest that the "all or none" character of the response is not present in red cells during the foetal stages of haematopoiesis.

Human neonatal red blood cells. An experimental model for the study of calcium-activated potassium channel refractoriness.

To study some characteristics of calcium-activated potassium channels free from plasma membrane lipid perturbations, neonatal red blood cells were selected. To this end, cells not previously treated (ATP depletion and/or reversible lysis) were exposed to the ionophore A23187 in a NO3 medium with calcium. The net efflux of potassium from the cells was studied. Preincubation in a medium devoid of potassium induced a significant decrease only in the rate constant of potassium flux. The data suggest that, in the absence of plasma membrane lipid impairment, changes in internal sites reactivity with calcium ions of channel proteins would be involved in the refractoriness. This would be at variance with channel density modifications.

Human neonatal red cells. Regulatory volume response under anisotonic conditions.

Studies have been carried out in human neonatal red cells (cord blood) to examine the outcome of cellular volume under anisotonic media. When exposed to hypertonicity these cells showed, after an initial shrinkage phase, a volume expansion that reached short of the original volume at 60 minutes. The chloride replacement by nitrate as well as amiloride (in chloride media) inhibited this regulatory volume response. The cellular sodium increase that paralleled the volume expansion was also amiloride-sensitive. We suggest that a Na+/H+ antiport mechanism could mediate the response. Cell volume increase in hypotonic media was not followed by a shrinkage phase.

Potassium influx in human neonatal red blood cells. Partition into its major components.

The potassium influx in human neonatal red blood cells (nRBC) shows an approximately 25% lower value compared to the total potassium influx in adult red blood cells (aRBC). The ouabain-sensitive potassium influx component represents approximately 70-75% of the total potassium influx for both types of cells but with an absolute value significantly lower in nRBC. In nRBC, the half maximum inhibitory effect for ouabain was obtained at a 10(-9) M concentration. The ouabain-insensitive nRBC potassium influx fractions showed two components: (i) a bumetanide-sensitive component, significantly lower than that of aRBC, (ii) a ouabain-bumetanide-insensitive (leak) component with a similar value in both cell types. The sum of the ouabain-sensitive and furosemide-sensitive components amounted in nRBC to a greater value than the total potassium influx. This behaviour could be interpreted as a superposition of the action of the inhibitors on the components affected.

Efecto de la bilirrubina no conjugada sobre los contenidos ionicos y la sensibilidad a hemolisis hiposmotica en eritrocitos. / Effect of unconjugated bilirubin on ionic contents and sensitivity to hyposmotic hemolysis in erythrocytes

Se estudio, in vitro, el efecto de la bilirrubina no conjugada sobre el contenido intracelular de sodio, potasio y cloruro, asi como la sensibilidad a hemolisis de eritrocitos humanos provenientes de adultos normales. Las modificaciones de los contenidos ionicos se relacionaron con la concentracion de bilirrubina libre en el medio de incubacion. El contenido de cloruro intracelular fue el mas sensible a la accion de la bilirrubina y la perdida desde las celulas se realizo contra su gradiente de concentracion. Se observo, ademas, un incremento significativo en la sensibilidad a la hemolisis hiposmotica, probablemente como consecuencia de la accion de la bilirrubina no conjugada (BNC) sobre la estructura de membrana. Se sugiere que la modificacion del contenido de cloruro en los eritrocitos podria ser un indice de la toxicidad celular de BNC y un criterio adicional a considerar en decisiones terapeuticas

Efecto de la bilirrubina no conjugada sobre los contenidos ionicos y la sensibilidad a hemolisis hiposmotica en eritrocitos. / Effect of unconjugated bilirubin on ionic contents and sensitivity to hyposmotic hemolysis in erythrocytes

Se estudio, in vitro, el efecto de la bilirrubina no conjugada sobre el contenido intracelular de sodio, potasio y cloruro, asi como la sensibilidad a hemolisis de eritrocitos humanos provenientes de adultos normales. Las modificaciones de los contenidos ionicos se relacionaron con la concentracion de bilirrubina libre en el medio de incubacion. El contenido de cloruro intracelular fue el mas sensible a la accion de la bilirrubina y la perdida desde las celulas se realizo contra su gradiente de concentracion. Se observo, ademas, un incremento significativo en la sensibilidad a la hemolisis hiposmotica, probablemente como consecuencia de la accion de la bilirrubina no conjugada (BNC) sobre la estructura de membrana. Se sugiere que la modificacion del contenido de cloruro en los eritrocitos podria ser un indice de la toxicidad celular de BNC y un criterio adicional a considerar en decisiones terapeuticas

Bilirubin adsorption in vitro by foetal and adult human erythrocytes.

Adsorption of bilirubin in vitro by human foetal erythrocytes from umbilical cords was significantly greater than the binding by adult erythrocytes. A difference in binding capacity was detected at 0.6 mmol/l bilirubin concentration (bilirubin/albumin ratio 2:1) immediately after mixing with the bilirubin solution. After 30 min incubation a further increase in bound bilirubin was found to be due only to binding in foetal cells. The results suggest that bilirubin from the medium was incorporated into at least two compartments in foetal erythrocytes. A possible role of human foetal erythrocytes in bilirubin distribution to tissues is stressed.

Effects of quinestrol on hepatic function in the rat.

Hepatic function in female rats given 200 microgram of quinestrol every 15 days for up to 210 days was studied. Prolonged treatment with quinestrol affected liver weight, serum cholestrol levels, biliar flux, and bromosulphthalein test, but these parameters tended toward control levels after 30 days of treatment. Quinestrol failed to affect alkaline phosphatase, oxalacetic and pyruvic transaminases and the concentration of bilirubin in serum and bile. The effects of quinestrol on hepatic function are similar to the effects of other estrogen derivatives.

Prednisone effects on postnatal brain development of rats following maternal therapy.

16-beta-Metilprednisone was administered in the last week of pregnancy in order to study its effects on postnatal brain development of the litters. Two groups of pregnant inbred rats were used for the experiments. Group I received 1.25 mg/kg/day 16-beta-metilprednisone. Group II served as untreated controls. The litters were killed either within 24 hr after birth, at 17 days, or at 45 days of age. Treated litters (animals whose mothers received the steroid) had a decreased body weight at 17 days of age. Wet brain weight was decreased in the same group. At 17 and 45 days of life treated rats showed a dry brain weight lower than that of controls. Newborn and 17-day-old rats whose mothers received the steroid showed a decreased content of brain proteins. Total lipids, cholesterol, and phospholipids were reduced in the brain of treated rats at 45 days of life. Brain phospholipids were also decreased in 17-day-old rats. These results show that 16-beta-metilprednisone administration to pregnant rats produces long lasting changes in brain chemical composition.