Vascular responsiveness to infused angiotensin II and to norepinephrine was determined in 14 normal subjects and two groups of diabetic subjects, 16 with no clinically detectable diabetic complications and 14 with diabetic retinopathy but no clinical evidence of nephropathy. All were maintained on a 100-mEq.-Na-100-mEq.-K diet. Serum electrolytes, 24-hour urinary sodium, creatinine clearance, and plasma renin activity did not differ significantly among the groups. Group mean baseline diastolic pressure in those with retinopathy was higher than in normal subjects but no significantly different from that of uncomplicated diabetics. The pressor dose of angiotensin II (ng./kg./min. to increase diastolic blood pressure 20 mm. Hg) for each group respectively was 11.5 ± 0.9, 12.9 ± 1.3, and 8.3 ± 1.3, and the slope of the dose-response curve (mm. Hg rise in blood pressure resulting from the infusion of 1 ng./kg./min. following the initial increment in blood pressure) was 2.0 ± 0.2, 1.6 ± 0.2, 3.3 ± 0.6. For norepinephrine, the pressor doses were 163 ± 24, 212 ± 21, and 123 ± 11 and slopes were 0.17 ± 0.03, 0.13 ± 0.02, and 0.20 ± 0.02. Neither diabetic group differed significantly from normal subjects. Diabetics with retinopathy were more sensitive to angiotensin II, pressor dose (P < 0.059) and slope (P < 0.02), and to norepinephrine, pressor dose (P < 0.006) and slope (P =0.05) than those without complications. These data suggest that vascular reactivity is enhanced in diabetics with retinopathy.

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