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RED-CELL OXYGEN AFFINITY AND 2,3-DIPHOSPHOGLYCERATE IN DIABETES
1179 RED-CELL OXYGEN AFFINITY AND
2,3-DIPHOSPHOGLYCERATE IN DIABETES SiR,-Dr. Ditzel (April 1, p. 721) suggested on the basis of measurements of the oxygen affinity of haemoglobin in vitro at fixed Pco2, that the intraerythrocytic concentra tion of 2,3-diphosphoglycerate (D.P.G.) is decreased in patients with diabetes mellitus. In view of the possible pathophysiological significance of this finding, we report measurements of D.P.G. and the actual oxygen affinity of red cells in normal individuals and in patients with juvenile diabetes. All subjects investigated were men. The actual oxygen affinity of red cells can be calculated from measurements of oxyhaemoglobin saturation and Po2 in anaerobic venous blood. Since in-vitro measurements imply application of a correction factor for pH effects on the oxygen affinity of heamoglobin (the Bohr correction), the value of which is not constant (varying with pH, PC02> and D.P.G. concentration 1), we consider a standardised measurement of the actual oxygen affinity more pertinent for the physiological evaluation of oxygen transport. Patients with juvenile diabetes were selected from a diabetes clinic, and only well-regulated, non-ketoacidotic patients were included. Samples were drawn early in the morning from fasting individuals (i.e., before the patients were to receive their morning insulin dose). Venous blood was sampled in heparinised glass syringes anaerobically from the antebrachial vein without applying stasis and after a minimum of 15 minutes’ rest of the arm. The samples were kept on ice for no more than 2 hours until the following measurements were carried out: Po2, pH, and PC02 0 Radiometer ’ microelectrodes), oxyhxmoglobin saturation (spectrophotometrically according to SiggaardAndersen et al.2), and D.P.G. (enzymatically according to Nygaard and Rorth 3). The results are shown in the accompanying table. The oxygen affinity of the red cells is expressed as actual P 50 (i.e., the oxygen tension giving 50% oxyhxmoglobin saturation at the prevailing pH and PC02) and is calculated from the measured P02 and oxyhxmoglobin saturation by of the Hill equation: Hb02/Hb+HbO2=K means (P02n)/1 + po2n), assuming a value for n of 2-8. Since the n value only varies insignificantly with pH, PC021 and D.P.G. concentration in near-physiological ranges, this equation can be used for calculation of P 50 as long as the oxyhaemoglobin saturation is in the range 20-80%. No significant differences in D.P.G. concentration or in the actual P50 were found. The unchanged D.P.G. concentration is in agreement with the results obtained by Dr. Alberti and colleagues (April 15, p. 843). Thus, direct measurements of red-cell oxygen affinity and D.P.G. do not support Dr. Ditzel’s hypothesis. The apparent discrepancy between our results and the results (and implications) of 1.
2.
Siggaard-Andersen, O., Rørth, M., Nørgaard-Pedersen, B., Sparre Andersen, O., Johansen, E. Scand. J. clin. Lab. Invest. (in the press). Siggaard-Andersen, O., Jørgensen, K., Naeraa, N. ibid. 1962,
3.
Nygaard,
14, 298.
AGE OF
S. F.,
Rørth, M. ibid. 1969, 24, 299.
SUBJECTS, DURATION
*
OF
nun.
DIABETES,
Hg.
t
Ditzel can probably be ascribed either to methodological differences or to application of improper correction factors. for pH effects on oxygen affinity. Rigshospitalet, 9 Blegdamsvej, Copenhagen, Denmark.
% * A copy of this letter reply follows.-ED. L.
went to
Dr.
Ditzel, and his,
SiR,-The data of Dr. Rorth and his colleagues indicatethat, when the diabetics are well controlled, the red-cell oxygen affinity is normal. These results are in agreement with my own experience, in that recent measurements ofthe average Pgo in 10 well-controlled diabetics was 26-3 ± 2-1 mm. Hg, as opposed to 26-6:1-4 mm. Hg in a comparable group of healthy controls. The reference byDr. Rorth and his co-workers to an as yet unpublished
article concerning the variability of the " Bohr " correction is, of course, very pertinent, and indicates that many more data must be accumulated before any firm conclusion can be reached. Department of Medicine, Aalborg Regional Hospital, Denmark. JØRN DITZEL.
DEVELOPMENTAL ASSESSMENT SiR,-We agree with Professor Illingworth (March 4, p. 532) about the clinical significance of primitive infantile reflexes. The items and abbreviations referred to by himdo not constitute parts of the Griffiths Mental Development Scale, which does not include neurological tests. We were careful to point out in our first letter that examination, particularly neurological examination, is necessary before conclusions are drawn in regard to mental status. As to who carries out psychological testing, there need not be a sharp definition of any boundary. Surely children are at the interface between medicine and psychology (not to mention education and sociology). Dr. Mary Sheridan has illustrated the point rather nicely by mentioning that Gesell was both medically and psychologically trained. Theassessment " team approach can help to avoid attitudes about watertight compartments, but, even so, a good deal of overlap is required before these compartments can become semi-permeable. This Association is a registered charity with membership from both the psychological and medical professions, and is designed to weld the expertise of both disciplines. We have to think in terms of educational medicine, and with the child health service advising parents, teachers, and others in authority not only in terms of medical diagnosis but also social syndromes, educational prognoses, and psychological projections for the child, his family, and his future. An examination of any child is, in our view, "
without some psychological assessment at certain stages, at least until adolescence and possibly afterwards for those handicapped. This is not to undervalue the importance of history-taking, physical examina-
incomplete
pH, P02, PC02’
per cent.
MIKAEL RØRTH H.-H. PARVING S. MUNKGAARD.
Department of Clinical Chemistry A,
OXYHaeMOGLOBIN SATURATION, D.P.G. ANAEROBIC VENOUS BLOOD
{ moles 2,3-diphosphoglycerate
per mole
CONCENTRATION,
haemoglobin
tetramer.
AND ACTUAL
P60
IN
2,3-DIPHOSPHOGLYCERATE IN DIABETES SiR,-Dr. Ditzel (April 1, p. 721) suggested on the basis of measurements of the oxygen affinity of haemoglobin in vitro at fixed Pco2, that the intraerythrocytic concentra tion of 2,3-diphosphoglycerate (D.P.G.) is decreased in patients with diabetes mellitus. In view of the possible pathophysiological significance of this finding, we report measurements of D.P.G. and the actual oxygen affinity of red cells in normal individuals and in patients with juvenile diabetes. All subjects investigated were men. The actual oxygen affinity of red cells can be calculated from measurements of oxyhaemoglobin saturation and Po2 in anaerobic venous blood. Since in-vitro measurements imply application of a correction factor for pH effects on the oxygen affinity of heamoglobin (the Bohr correction), the value of which is not constant (varying with pH, PC02> and D.P.G. concentration 1), we consider a standardised measurement of the actual oxygen affinity more pertinent for the physiological evaluation of oxygen transport. Patients with juvenile diabetes were selected from a diabetes clinic, and only well-regulated, non-ketoacidotic patients were included. Samples were drawn early in the morning from fasting individuals (i.e., before the patients were to receive their morning insulin dose). Venous blood was sampled in heparinised glass syringes anaerobically from the antebrachial vein without applying stasis and after a minimum of 15 minutes’ rest of the arm. The samples were kept on ice for no more than 2 hours until the following measurements were carried out: Po2, pH, and PC02 0 Radiometer ’ microelectrodes), oxyhxmoglobin saturation (spectrophotometrically according to SiggaardAndersen et al.2), and D.P.G. (enzymatically according to Nygaard and Rorth 3). The results are shown in the accompanying table. The oxygen affinity of the red cells is expressed as actual P 50 (i.e., the oxygen tension giving 50% oxyhxmoglobin saturation at the prevailing pH and PC02) and is calculated from the measured P02 and oxyhxmoglobin saturation by of the Hill equation: Hb02/Hb+HbO2=K means (P02n)/1 + po2n), assuming a value for n of 2-8. Since the n value only varies insignificantly with pH, PC021 and D.P.G. concentration in near-physiological ranges, this equation can be used for calculation of P 50 as long as the oxyhaemoglobin saturation is in the range 20-80%. No significant differences in D.P.G. concentration or in the actual P50 were found. The unchanged D.P.G. concentration is in agreement with the results obtained by Dr. Alberti and colleagues (April 15, p. 843). Thus, direct measurements of red-cell oxygen affinity and D.P.G. do not support Dr. Ditzel’s hypothesis. The apparent discrepancy between our results and the results (and implications) of 1.
2.
Siggaard-Andersen, O., Rørth, M., Nørgaard-Pedersen, B., Sparre Andersen, O., Johansen, E. Scand. J. clin. Lab. Invest. (in the press). Siggaard-Andersen, O., Jørgensen, K., Naeraa, N. ibid. 1962,
3.
Nygaard,
14, 298.
AGE OF
S. F.,
Rørth, M. ibid. 1969, 24, 299.
SUBJECTS, DURATION
*
OF
nun.
DIABETES,
Hg.
t
Ditzel can probably be ascribed either to methodological differences or to application of improper correction factors. for pH effects on oxygen affinity. Rigshospitalet, 9 Blegdamsvej, Copenhagen, Denmark.
% * A copy of this letter reply follows.-ED. L.
went to
Dr.
Ditzel, and his,
SiR,-The data of Dr. Rorth and his colleagues indicatethat, when the diabetics are well controlled, the red-cell oxygen affinity is normal. These results are in agreement with my own experience, in that recent measurements ofthe average Pgo in 10 well-controlled diabetics was 26-3 ± 2-1 mm. Hg, as opposed to 26-6:1-4 mm. Hg in a comparable group of healthy controls. The reference byDr. Rorth and his co-workers to an as yet unpublished
article concerning the variability of the " Bohr " correction is, of course, very pertinent, and indicates that many more data must be accumulated before any firm conclusion can be reached. Department of Medicine, Aalborg Regional Hospital, Denmark. JØRN DITZEL.
DEVELOPMENTAL ASSESSMENT SiR,-We agree with Professor Illingworth (March 4, p. 532) about the clinical significance of primitive infantile reflexes. The items and abbreviations referred to by himdo not constitute parts of the Griffiths Mental Development Scale, which does not include neurological tests. We were careful to point out in our first letter that examination, particularly neurological examination, is necessary before conclusions are drawn in regard to mental status. As to who carries out psychological testing, there need not be a sharp definition of any boundary. Surely children are at the interface between medicine and psychology (not to mention education and sociology). Dr. Mary Sheridan has illustrated the point rather nicely by mentioning that Gesell was both medically and psychologically trained. Theassessment " team approach can help to avoid attitudes about watertight compartments, but, even so, a good deal of overlap is required before these compartments can become semi-permeable. This Association is a registered charity with membership from both the psychological and medical professions, and is designed to weld the expertise of both disciplines. We have to think in terms of educational medicine, and with the child health service advising parents, teachers, and others in authority not only in terms of medical diagnosis but also social syndromes, educational prognoses, and psychological projections for the child, his family, and his future. An examination of any child is, in our view, "
without some psychological assessment at certain stages, at least until adolescence and possibly afterwards for those handicapped. This is not to undervalue the importance of history-taking, physical examina-
incomplete
pH, P02, PC02’
per cent.
MIKAEL RØRTH H.-H. PARVING S. MUNKGAARD.
Department of Clinical Chemistry A,
OXYHaeMOGLOBIN SATURATION, D.P.G. ANAEROBIC VENOUS BLOOD
{ moles 2,3-diphosphoglycerate
per mole
CONCENTRATION,
haemoglobin
tetramer.
AND ACTUAL
P60
IN