STIMULATION OF IMMUNOREACTIVE INSULIN AND HUMAN GROWTH HORMONE RELEASE BY ADMINISTRATION OF ARGININE IN PATIENTS WITH DIABETIC RETINOPATHY

ABSTRACT The effect of arginine hydrochloride (30 g), given twice at 90 min intervals, on the release of immunoreactive insulin and of human growth hormone was studied in healthy subjects (HS), in diabetics without and with various degrees of retinopathy and in acromegalics. The insulinogenic index estimated by the ratio of μU IRI per ml/mg per 100 ml of blood glucose was maximal in HS after the first administration of arginine. It was highest in acromegalics and diminished in all the diabetic subjects. The release of human growth hormone as estimated by the mean sum of increments above the basal levels (x̄ + sem) during period I and II was 80.2±15 ng/ml and 59.0±18 ng/ml in HS (n = 7), 38±8.6 ng/ml and 36±16.3 ng/ml in diabetics without retinopathy (n = 9), 4.2±0.4 ng/ml and 19±7 ng/ml in insulin treated diabetics with retinopathy (n = 9), and 22.7±10.7 ng/ml and 46±10.5 ng/ml in orally treated diabetics with retinopathy (n = 7). Patients suffering from proliferative retinopathy (n = 9) exhibited values of 32.8±10.6 ng/ml during period I and 43.5±10.6 ng/ml during period II. The secretory response of HGH to arginine in acromegalics (n = 6) was not significant. The data reported suggest an impaired secretory capacity for the release of human growth hormone to the administration of arginine in patients with diabetic retinopathy. The observations do not support the hypothesis that an exaggerated release of HGH plays a role in the development of diabetic retinopathy.