Glycosylated hemoglobin was measured, by a colorimetric method, in 49 patients with sickle cell anemia attending Khartoum Teaching Hospital. The level obtained (4.9%, SD 1.3) was significantly lower than the control value (5.6%, SD 0.2; p < 0.0025). Expressed as percentage of the control value, the glycosylated hemoglobin level in these patients was 81 %. This falls midway between the 90% reported in a benign form of sickle cell anemia in Saudi Arabia and the 58% reported in a severe form in an American Black group, which gives support to the observed heterogeneity of sickle cell anemia. Alternatively, glycosylated hemoglobin level in 27 subjects with sickle cell trait (5.6%, SD 0.2) was identical to that of the controls. The state of hemolysis in the sickle cell anemia patients, as indicated by bilirubin levels, did not correlate with the glycosylated hemoglobin values. Although glycosylated hemoglobin measurement is affected by red cell survival, it does not reflect the state of ongoing hemolysis.

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The effects of glucose and arginine on insulin secretion in the presence of glucagon antibodies were investigated in rats in vivo. In contrast to controls, animals given glucagon antibodies showed an inhibition of arginine-stimulated (p less than 0.001), but not glucose-stimulated, insulin secretion. That these effects were not due to incomplete neutralisation of endogenous glucagon is evidenced by the presence of large antibody excess throughout the duration of the experiments. Both the glucagonotropic effect of arginine (319 +/- 60 ng/l, p less than 0.01) and the insulinotropic effect of exogenous glucagon (8.3 +/- 0.8 microgram/l, p less than 0.001) were demonstrable under our experimental conditions in the absence of exogenous glucagon antibodies. These observations suggest that different mechanisms are involved in the stimulation of insulin release by arginine and by glucose, and that glucagon may play an important physiological role in the mediation and regulation of insulin secretion by secretogogues, such as arginine.

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