Redistribution of blood volume in Type I diabetes

Aims/hypothesis. Impaired activity of endothelium-derived nitric oxide in T ype I (insulin-dependent) diabetes mellitus will cause an increased vascula r tone. Considering the lower production of nitric oxide in veins than in a rteries, an impaired activity would have less vasoconstrictive effect in ve ins. The reported minimally changed total plasma volume in diabetes might, therefore, indicate a redistribution of blood volumes from the arterial to the venous side of the circulation. This could be more pronounced in patien ts with microalbuminuria. Methods. In 16 normoalbuminuric and 16 microalbuminuric Type I diabetic pat ients and 16 individually matched healthy control subjects, venous and arte rial blood volumes, venous myogenic response and arterial distensibilities were assessed in the upper arm using an electrical bio-impedance method. Results. In diabetic patients, the venous blood volume and venous myogenic response were increased (p < 0.02 and p < 0.05, respectively), whereas the arterial blood volume did not change. Moreover, in diabetic patients the di stensibility of the large arteries was decreased (p < 0.05) but increased i n the total arterial bed (p < 0.05). Therefore, the distensibility of the s mall arteries must have been increased. No differences were found between n ormoalbuminuric and microalbuminuric diabetic patients. Conclusion/interpretation. The increase in venous blood volume and myogenic response and the decrease in distensibility of the large arteries in the u pper arm are in agreement with the expected shift towards venous blood volu me distribution in Type I diabetes with and without microalbuminuria. Furth ermore, they support the haemodynamic hypothesis of the pathogenesis of dia betic microangiopathy.