Factors in the control of plasma renin activity and concentration in Type 1 (insulin-dependent) diabetes

Increased red cell sodium lithium countertransport activity, total exchangeable sodium, and hormonal control of sodium balance in normoalbuminuric type 1 diabetes

The relationship between erythrocyte sodium lithium countertransport activity (SLC), total exchangeable sodium (NaE), and hormonal control of renal function was examined in 40 normotensive, normoalbuminuric, non-neuropathic Type 1 diabetic subjects, of whom 8 had elevated SLC (> 0.40 mmol Li h-1l-1 rbc). Eleven health controls with normal SLC, who were of comparable age, body mass, and blood pressure were also studied. By contrast with healthy controls, SLC in Type 1 diabetes was not associated with plasma renin activity (PRA), aldosterone, systolic blood pressure or lean body mass. SLC was also unrelated to atrial natriuretic peptide (ANP) (Type 1 diabetes only) and NaE. NaE was not correlated with any other variables. The relationships between PRA and aldosterone in healthy controls were retained in Type 1 diabetes (R2 0.37 supine, p = 0.00001, and 0.27 ambulant, p = 0.0005), as were respective direct and inverse relations between vasopressin and ANP and both PRA (rs 0.54 to 0.57, rs -0.43 to -0.53), and aldosterone (rs 0.78 to 0.80, rs -0.71 to -0.80). Fasting free serum insulin and vasopressin were both inversely related to ANP (rs -0.91 and -0.71, respectively). In the absence of autonomic dysfunction, hypertension or early nephropathy in Type 1 diabetes, increased SLC or exchangeable sodium were unrelated to each other or with hormonal control of sodium balance, but the homeostatic factors controlling hormonal interaction appear to be maintained. The interaction between insulin and hormonal control of sodium and water balance may be modified by circulating free insulin concentrations.

The activity of the renin-angiotensin-aldosterone system before and during submaximal bicycle exercise in relation to circulatory catecholamines in patients with type 1 (insulin-dependent) diabetes mellitus

To evaluate the renin-angiotensin-aldosterone system in relation to circulatory catecholamines, we determined renin activity, angiotensin II, aldosterone, adrenaline, and noradrenaline in plasma before and during a submaximal bicycle exercise test in 23 Type 1 (insulin-dependent) diabetic patients (aged 19-57 years, mean 37; duration of diabetes 2-32 years, mean 16), 17 with signs of cardiac autonomic neuropathy, and in 18 healthy non-diabetic subjects (aged 24-41 years, mean 29). At rest, Type 1 diabetic patients showed significantly lower aldosterone values than control subjects (0.14 +/- 0.02 nmol/l and 0.22 +/- 0.02 nmol/l; p less than 0.01) while renin activity (1.0 +/- 0.1 nmol.l-1.h-1 and 0.9 +/- 0.1 nmol.l-1.h-1) and angiotensin II (14 +/- 1 nmol/l and 18 +/- 2 nmol/l) did not differ significantly between patients and control subjects. During exercise, increments (increase from the resting value to the value at 80% of maximal working capacity) in renin (1.5 +/- 0.4 nmol.l-1.h-1 and 3.7 +/- 0.5 nmol.l-1.h-1; p less than 0.001), angiotensin II (28 +/- 8 nmol/l and 60 +/- 8 nmol/l; p less than 0.001), aldosterone (0.16 +/- 0.04 nmol/l and 0.25 +/- 0.05 nmol/l; p less than 0.05), adrenaline (1.96 +/- 0.49 nmol/l and 2.92 +/- 0.51 nmol/l; p less than 0.05), and noradrenaline (12.01 +/- 1.25 nmol/l and 18.74 +/- 1.45 nmol/l; p less than 0.01) were significantly lower in the patients than in control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Central role for sodium in the pathogenesis of blood pressure changes independent of angiotensin, aldosterone and catecholamines in type 1 (insulin-dependent) diabetes mellitus

We studied 73 Type 1 (insulin-dependent) diabetic patients, 18 to 50 years of age, with a diabetes duration of more than five years. Group 1: normal urinary albumin excretion below 30 mg per 24 h (n = 19); group 2: microalbuminuria, 30-300 mg per 24 h (n = 36); and group 3: diabetic nephropathy, above 300 mg per 24 h (n = 18). Fifteen nondiabetic persons matched for sex and age served as control subjects. The sodium intake evaluated on the basis of 24-h urine sodium excretion was similar in patients and control subjects. Blood pressure in groups 1 and 2 and control subjects was below 160/95 mmHg. The blood pressure was increased in group 3 as compared with the other groups (systolic/diastolic 161 +/- 22/101 +/- 9 mmHg vs 131 +/- 13/84 +/- 10, mean +/- SD, p less than 0.0001). Exchangeable sodium was increased in patients (p less than 0.01) and correlated to the mean blood pressure (n = 70, r = 0.41, p less than 0.01). Extracellular volume was increased in patients (p less than 0.05), whereas plasma volume was normal. Supine serum angiotensin II was suppressed in the patients (p less than 0.001). A negative correlation was found between mean blood pressure and supine serum aldosterone (n = 68, r = -0.24, p less than 0.05), and exchangeable sodium and aldosterone (n = 66, r = -0.36, p less than 0.002) in all patients. The catecholamine levels were also suppressed or normal in the patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased vasopressor responsiveness to angiotensin II in type 1 (insulin-dependent) diabetic patients without complications

The blood pressure response to infused angiotensin II (0.3 to 3 ng X kg-1 X min-1) was investigated in six normotensive patients with Type 1 (insulin-dependent) diabetes free of complications and in six healthy subjects matched for age, sex and weight. Basal blood pressures (111/68 and 114/72 mmHg) and basal plasma angiotensin II levels (18.0 +/- 5.2 and 14.1 +/- 2.4 pmol/l; mean + SD) were similar in the diabetic and control groups as were 24 h urinary excretions of sodium (157 +/- 88 and 154 +/- 84 mmol/24 h). Equal increments in plasma angiotensin II were produced during the infusions in the two groups. Increases in both diastolic and systolic blood pressure were significantly greater in the diabetic patients throughout the infusion. Mean diastolic increments were: 6.7 versus 1.3 mmHg (0.3 ng dose), 11.0 versus 6.9 mmHg (1 ng dose) and 16.7 versus 12.3 mmHg (3 ng dose) (p less than 0.001). Corresponding figures for systolic pressure were: 8.7 versus 1.3 mmHg, 10.3 versus 3.7 mmHg and 15.3 versus 8.7 mmHg (p less than 0.001). Vasopressor responsiveness to angiotensin II is thus increased in Type 1 diabetic patients without complications; it may, therefore, be a consequence of the diabetes rather than of the presence of microvascular disease or hypertension.