Association in Long-Evans hooded rats of red cell 2,3-diphosphoglycerate levels with hemoglobin types

Erythrocyte isozymes of phosphofructokinase in genetically high- and low-2,3-diphosphoglycerate rats

A major locus (Dpg) with two alleles (d and D) controls erythrocyte 2,3-diphosphoglycerate (DPG) levels in Long-Evans rats and is closely linked to a locus (Hbb) determining a hemoglobin electrophoretic polymorphism. Glycolytic intermediate levels and phosphofructokinase (PFK) kinetic studies suggest that in vivo PFK activity differences underlie the differences in DPG levels. We report here chromatographic and immunologic evidence that rat erythrocyte PFK is composed of two isozymes which elute from DEAE-Sephadex at positions identical to those of the isozymes in platelets and liver, respectively. The percentage of platelet-type PFK is significantly (P less than 0.05) smaller in low-DPG (dd) hemolysates than in DD hemolysates regardless of hemoglobin phenotype. When hemolysates were prepared in a stabilizing buffer, PFK specific activity was significantly (P less than 0.005) higher in DD rats. These data suggest that the PFK kinetic differences may result from alterations in the isozyme composition of active PFK.

Hemoglobin polymorphism in inbred strains of rats (Rattus norvegicus)

Hemoglobin phenotypes A and B were determined by polyacrylamide gel electrophoresis of erythrocyte lysates from 29 inbred strains of rats. Fourteen strains have phenotype A and fifteen have phenotype B, which are characterized by five and six hemoglobin bands, respectively. Breeding studies showed that the phenotypes are codominant and that they segregate in a simple Mendelian fashion in the (A x B) F1 x A backcross. Sex and hemoglobin phenotype assort independently, and the hemoglobin phenotype is not linked to the major histocompatibility complex (RT1) and to two erythrocyte alloantigenic systems (RT2 and RT3).

2,3-diphosphoglycerate in high- and low-altitude populations of the deer mouse

Erythrocyte DPG concentrations were studied in populations of Peromyscus maniculatus native to different altitudes. Deer mice native to, and resident at, high altitude showed higher DPG/Hb ratios than did deer mice native to, and resident at, low altitude. However, after prolonged acclimation to low altitude, the high-altitude natives showed lower DPG/Hb ratios than did low-altitude natives. The differences in baseline DPG levels appear to be determined primarily by genetic factors. The heritability (h2) of DPG/Hb ratios was estimated by two independent methods to be 0.51 and 0.66, but those values are inflated to an unknown extent by environmental correlations between relatives. Mild cold stress did not elicit an increase in DPG/Hb ratios. DPG levels tended to decrease with age, but the aging effect was not consistently observed in all samples. Neither sex nor alpha-globin genotype influenced DPG levels. The adaptive significance of the genetic differences in DPG metabolism between high- and low-altitude populations remains problematic.

Erythrocyte phosphofructokinase in rat strains with genetically determined differences in 2,3-diphosphoglycerate levels

We have studied the erythrocyte enzyme phosphofructokinase (PFK) from two strains of Long-Evans rats with genetically determined differences in erythrocyte 2,3-diphosphoglycerate (DPG) levels. The DPG difference is due to two alleles at one locus. With one probable exception, the genotype at this locus is always associated with the hemoglobin (Hb) electrophoretic phenotype, due to a polymorphism at the III beta-globin locus. The enzyme PFK has been implicated in the DPG difference because glycolytic intermediate levels suggest that this enzyme has a higher in vivo activity in High-DPG strain rats, although the total PFK activity does not differ. We report here that partially purified erythrocyte PFK from Low-DPG strain cells is inhibited significantly more at physiological levels of DPG (P less than 0.01) than PFK from High-DPG strain erythrocytes. Citrate and adenosine triphosphate also inhibit the Low-DPG enzyme more than the High-DPG enzyme. Therefore, a structurally different PFK, with a greater sensitivity to inhibitors, may explain the lower DPG and ATP levels observed in Low-DPG strain animals. These data support a two-locus (Hb and PFK) hypothesis and provide a gene marker to study the underlying genetic and physiologic relationships of these loci.

Rat hemoglobin heterogeneity: postnatal changes in proportions of multiple components and effects of erythropoietin on marrow cell cultures

Hemolysate from adult and newborn rats was fractionated into nine components (I-IX) using DEAE-cellulose chromatography. A subsequent chromatographic step resolved component IV into two, IVa and Ivb. A comparison of adult and newborn rat hemolysates showed that newborn had higher levels of components I, II, and IV. In the newborn, they accounted for 52% of total hemoglobin eluted, compared to 36% in the adult. Components V, VI, and VIII were less in the newborn than in the adult red cell, at 42% compared to 59%. Minor components III, VII, and IX were unchanged, at 5.8% in newborn and 5.3% in adult rats. Bone marrow cells from adult rats cultured for 46 hours, showed stimulation of eight components under the influence of erythropoietin (components IVa and IVb were not distinguished, and VII was not detected). The extent of stimulation was not consistently higher for major than for minor hemoglobins. These data show that adult rats possess at least ten hemoglobin components, that newborn rats have the same components but in different proportions, and that both major and minor components are stimulated by erythropoietin in bone marrow cell cultures.

Rat embryonic and foetal erythrocytes. High 2,3-bisphosphoglycerate and ATP and low oxygen affinity in vitro for nucleated embryonic cells

Embryonic nucleated red cells of the rat have high ATP and 2,3-bisphosphoglycerate and relatively low oxygen affinity. During foetal life they are replaced by large non-nucleated red cells with high ATP, low bisphosphoglycerate and high oxygen affinity. After birth, small non-nucleated red cells with high bisphosphoglycerate and low oxygen affinity rapidly predominate.