Chloride and bicarbonate transport in chick embryonic red blood cells.

1. Unidirectional efflux of 36Cl- and H14CO3- from erythrocytes of 4- to 16-day-old chick embryos was measured under steady-state conditions at 37 degrees C and pH 7.7. The efflux rates were high, > 3 s-1, and were, therefore, measured by means of the continuous flow tube method. 2. At day 4 of development the range of permeability coefficients for bicarbonate and chloride (PHCO3 and PCl was 1-30 x 10(-4) cm s-1, with average values of respectively 10 x 10(-4) and 8 x 10(-4) cm s-1. However, the results can be divided into two groups, one with PHCO3 and PCl above 12 x 10(-4) cm s-1, and one with values below 5 x 10(-4) cm s-1. The same range of values was also obtained for day 6 erythrocytes, but the overlap is more conspicuous. At day 16, PHCO3 and PCl were respectively 9 x 10(-4) and 6 x 10(-4) cm s-1 (37 degrees C, pH 7.7). In adult chicken red blood cells PHCO3 and PCl were respectively 7 x 10(-4) and 4 x 10(-4) cm s-1, and in human red blood cells the respective values were 5.6 x 10(-4) and 4 x 10(-4) cm s-1. 3. Chloride self-exchange, measured at 0 degrees C, was almost completely inhibited by addition of 1 mM 4,4'-diisothiocyanostilbene-2,2'-disulphonate (DIDS) at both days 6 and 16 of embryonic development, supporting the finding that the embryonic chick erythrocytes also have a transmembrane anion exchanger similar to that of other red cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Control of cell pH in immature primitive red cells from chick embryo.

1. The intracellular pH in primitive red cells from 4 day chick embryos was measured with the digitonin null-point method and the fluorescent indicator SNARF-1. At physiological pHe of 8.0 red cell pH is 7.39 at day 4. 2. The calculated proton equilibrium potential of -38 mV is in good agreement with previous measurements of Em (Engelke et al., 1988) and supports the conclusion that the Em is dominated by a proton conductance. 3. The sodium-proton exchanger is present in primitive red cells but quiescent under physiological conditions. 4. The results indicate that the bicarbonate-chloride exchange via Band 3 protein is impaired.

Measurement of pH in blood vessels and interstitium of 4 and 6 days-old chick embryos.

The pH in intra- and extraembryonic blood vessels and in the embryonic interstitium has been measured in 4 and 6 days-old chick embryos using pH microelectrodes. The mean pH of the lateral vitelline vein was 8.0 at day 4 and 7.89 at day 6 and that of the vitelline artery 7.8 and 7.66, respectively. The pH of the blood in the embryonic heart was the same at day 4 and 6 (7.68 and 7.67). The lowest blood pH was recorded in the jugular vein (7.42 at day 6). The pH values measured in the interstitium show less variability. However a clear cranio-caudal gradient was apparent at day 4 where pH fell from 7.68 to 7.47. At day 6 the pH values of the interstitium ranged between 7.61 and 7.52 showing no preferential distribution. Using previously determined values for blood PO2 and the oxygen haemoglobin equilibrium curves, we calculated the oxygen saturation of the blood at the measured pH. In the vitelline vein the O2 saturation is 89% at day 4 and more than 95% at day 6, whereas that of the vitelline artery is 37% and 25%, respectively. When ambient PCO2 is raised to about 8 torr the pH falls to 7.81 (7.68) in the vitelline vein at day 4 (6) and the oxygen saturation decreases to 64% and 79%, respectively. Thus the high pH values found in the vitelline vein seem to be necessary for adequate oxygen uptake of the embryo.