Active transport into the human erythrocyte; evidence from comparative kinetics and competition among monosaccharides

1. Applicability of the previously postulated active transport system for conveying glucose into the human red cell was tested in connection with a number of related substances, comprising 6-carbon aldoses and ketoses, 5-carbon aldoses, and 5- or 6-carbon polyhydric alcohols. 2. The alcohols did not perceptibly penetrate the cells; all the sugars penetrated, the rates differing, but all of the same order of magnitude. 3. All the aldoses penetrated according to the pattern previously reported for glucose, in that the rate of penetration was not directly related to the gradient, but subject to some limiting factor. 4. The ketoses penetrated approximately according to the pattern of passive diffusion. 5. When present in equal concentrations, any aldose prevented or greatly delayed the entrance of a ketose, while the ketose did not perceptibly alter the rate of aldose uptake. Within each class, similar inhibitory relations were observed. 6. Penetration of all the sugars showed a high temperature coefficient and was inhibited by the mercuric ion or p-chloromercuribenzoate; certain of the sugars showed a residual degree of penetration not thus inhibitable. 7. Penetration of the ketoses was selectively inhibited by barbital. 8. These observations are interpreted in terms of simple equilibria between the various sugars and a hypothetical carrier molecule in the membrane, with which the sugars form a complex during their passage through the membrane. Comparisons between the sugars in relation to their reactions with the carrier system are indicated.

A theoretical study of the influence of diffusion and chemical reaction velocity on the rate of exchange of carbon monoxide and oxygen between the red blood corpuscle and the surrounding fluid

Numerical methods have been applied to the problem of the diffusion of CO and O 2 through the red blood corpuscle membrane, accompanied by diffusion and chemical reaction of these substances in the layer of concentrated haemoglobin solution inside the corpuscle. The methods are applied to recent data on (i) the rates of CO uptake by corpuscle suspensions and haemoglobin solutions, prepared from the blood of rams and pregnant ewes, (ii) the rates of O 2 egress from ram corpuscle suspensions and haemoglobin solutions. In the case of the ram blood the slower overall rates of exchange in the corpuscle suspensions, as compared with the haemoglobin solution, can be accounted for by the limiting effect of diffusion inside the corpuscle, without the necessity of attributing any limiting effect to the corpuscle membrane. In the pregnant ewe blood, on the other hand, the corpuscle membrane appears to have a definite limiting effect on the passage of CO and preliminary values of its permeability to this substance are given. It is also shown how the special methods, of computation developed in this paper can be generalized and thus made applicable to other processes in which diffusion and chemical reaction velocity are jointly involved.

Erythrocyte life span in growing swine as determined by glycine-2-C14

Red blood cell survival studies were performed on five normal growing swine by following the C(14)-specific activity of hemoglobin and heme after the administration of glycine-2-C(14). The erythrocytes of normal growing swine appear to be destroyed both by a random and an age-dependent process. Random destruction accounts for the larger portion of the cells which are destroyed. The "mean" red cell survival time was 62 days. This represents the interval from the time of incorporation of 50 per cent of the maximal amount of labelling achieved to the time when the level had decreased once more to the 50 per cent amount. The " 'corrected' average potential life span" of the red cells was 86 +/- 11.5 days. This figure was obtained by subtracting the number of days required to attain 80 per cent of the maximal labelling from the average survival time of red cells destroyed by an age-dependent process as distinguished from random destruction.

The specific heat and the heat of compression of human red cells, sickled red cells, and paracrystalline rat red cells

The investigation of two thermal properties of red cells throws some light on whether sickling is a process involving the crystallization of a relatively insoluble hemoglobin. These properties are the specific heat and the heat of compression, both of which would be expected to become numerically less if the hemoglobin of the red cell were to crystallize. In the case of paracrystalline rat red cells, which give spacings at 45 A and 58 A by x-ray diffraction, the specific heat is reduced to 85 per cent of that of the normal red cells, and the heat of compression is only about 75 per cent of that found for the normal red cell. In the case of the red cell sickled by a reduction of the O₂ tension, the specific heat and the heat of compression are substantially the same as found for the normal red cell. This is an argument against sickling being the result of a crystallization process, and supports the observation that sickled cells do not give x-ray spacings. The result is compatible, on the other hand, with sickling being the result of the formation of an oriented and birefringent gel.