Diabetic nephropathy and arterial hypertension. The effect of antihypertensive treatment

Our longitudinal study of urinary albumin excretion rate in long-term insulin-dependent diabetics without proteinuria (negative albustix) suggests that early detection of patients at high and low risk of developing persistent proteinuria, i.e., diabetic nephropathy, is possible by using a sensitive method for albumin determination. Our prospective studies in young insulin-dependent diabetics with diabetic nephropathy show that the rate of decline in glomerular filtration rate (GFR) varies considerably, with a mean of 0.75 ml/min/mo and a range from 0.1 to 1.50 ml/min/mo, and that an increase in arterial blood pressure to a hypertensive level is an early feature; 43% of the patients had diastolic blood pressure greater than 100 mm Hg. Early and aggressive antihypertensive treatment reduces both albuminuria and the rate of decline in GFR in young patients with diabetic nephropathy.

The effect of strict short-term metabolic control on retinal nervous system abnormalities in newly diagnosed Type 1 (insulin-dependent) diabetic patients

The oscillatory potential of the electroretinogram and the initial 2-min phase of dark-adaptation were studied in seven newly diagnosed Type 1 (insulin-dependent) diabetic patients before and during initial insulin treatment. Strict metabolic control was achieved in all seven patients using multiple subcutaneous injections of insulin. Seven to 11 days of strict metabolic control improved the added amplitude value of the oscillatory potential from 236 +/- 8 to 268 +/- 8 microV (mean +/- SEM; p less than 0.01) and the dark-adaptation from 90 +/- 5 to 67 +/- 5 s (p less than 0.01). Our study has demonstrated reversible neurophysiological abnormalities in the diabetic retina which are related to metabolic control.

Hearing sensitivity in patients with myxoedema before and after treatment with l-thyroxine

Fifteen patients with confirmed myxoedema, median age 76 years, were consecutively referred for audiological evaluation. The diagnosis of myxoedema was based on the symptomatology, typical clinical appearance, increased TSH level and decreased T4. The audiological evaluation included routine ENT-examination, pure-tone octave audiometry, determination of speech reception threshold and discrimination score. The function of the middle ear was evaluated by impedance audiometry, indicating both middle ear pressure and stapedial reflex thresholds elicited by contralateral stimulation. All patients were evaluated in the myxoedematous state before treatment with l-thyroxine and reevaluated when treated and found euthyroid, both by the clinical investigation and as judged by chemical thyroid parameters. Bilateral symmetrical or nearly symmetrical sensorineural hearing loss was demonstrated in all patients before treatment. The results indicate that in elderly patients with myxoedema no improvement in hearing sensitivity can be demonstrated upon l-thyroxine medication. Patients with myxoedema at this age demonstrate neither more nor less degree of hearing loss when related to an age-matched group of hearing impaired patients. In patients with myxoedema the hearing impairment is found to be equal to that of an age and sex matched control group exhibiting true age-related hearing loss.

Vitamin D metabolism in insulin-dependent diabetes mellitus

A significant loss of bone has been observed in diabetes mellitus. The pathogenesis is unknown, but an impairment of vitamin D metabolism might be involved. Consequently, we have studied vitamin D metabolism in five groups of insulin-dependent diabetic patients. Significantly reduced levels of serum 25(OH)D were seen only in patients with diabetic nephropathy. The serum levels of 1,25 (OH)2D were reduced only in diabetic ketoacidosis but normalized during recovery. It is concluded that vitamin D metabolism is largely normal in adult insulin-dependent diabetes, and it seems unlikely that a disturbance of the vitamin D metabolism can explain the bone loss in the ordinarily controlled diabetics.

Diabetic nephropathy and arterial hypertension

The relationship between arterial blood pressure and diabetic nephropathy was examined in 61 Type 1 (insulin-dependent) diabetic patients (22 females and 39 males). All patients fulfilled the following criteria: persistent proteinuria (greater than 0.5 g/day), onset of diabetes before 31 years of age, age less than 42 years, serum creatinine less than 130 mumol/l, and no antihypertensive treatment. Thirty Type 1 diabetic patients without persistent proteinuria but matched for sex, age, ideal body weight and duration of diabetes, and 30 healthy subjects matched for sex, age and ideal body weight were also studied as controls. The diabetic patients with persistent proteinuria had elevated blood pressures (146/96 +/- 17/10 mmHg, mean +/- SD) compared with 123/75 +/- 11/8 mmHg in diabetic patients without persistent proteinuria, and normal subjects (120/77 +/- 6/6 mmHg; p less than 0.001 for each). Diastolic blood pressure greater than or equal to 95 mmHg was found in 51% of the group with persistent proteinuria. Elevated arterial blood pressure is frequently present in young Type 1 diabetic patients with diabetic nephropathy and normal serum creatinine.

Decreased distensibility of a passive vascular bed in diabetes mellitus: an indicator of microangiopathy?

This study was undertaken to determine whether the distensibility of a passive vascular bed is reduced in Type 1 (insulin-dependent) diabetic patients with microangiopathy. The change in blood flow induced by 45 degrees head-up tilting was studied in two systems: (a) following maximal ischaemic exercise and (b) in a vascular bed locally paralysed by the injection of papaverine. Five normal subjects, six patients with long-standing Type 1 diabetes and six non-diabetic patients with severe atherosclerosis affecting the legs were studied. Blood flow was measured in the anterior tibial muscle by the isotope washout technique. The median increase in blood flow produced by tilting was greater in normal subjects than in diabetic subjects in both the locally-relaxed bed (58% and 14% respectively) and after maximal ischaemic exercise (45% and 4% respectively). In the atherosclerotic subjects, the increase in blood flow in the locally relaxed bed was 77%. The results are consistent with the hypothesis that the reduced distensibility seen in the diabetic subjects was related to the presence of microvascular disease and that the behaviour of a vascular bed relaxed by the local injection of papaverine might be an appropriate model to study this condition.

Increased transvascular escape rate and lymph drainage of albumin in pigs during intravenous diuretic medication. Relations to treatment in man and transport mechanisms

Transvascular escape rate of albumin (TERalb, i.e. the fraction of intravascular mass of albumin (IVMalb) passing to (or during steady state returning from) the extravascular space per unit time) was determined from the initial disappearance rate of i.v. injected radioiodinated serum albumin in anaesthetized pigs during control conditions and during diuretic medication (furosemide i.v. 20 mg/15 min, total 160-200 mg). During diuretic medication TERalb (mean 17.1% IVMalb X h-1, range 11.5-21, n = 6) increased significantly above the control period (mean 12.3% IVMalb X h-1, range 9.5-16.5, P less than 0.05). Pressures in artery, right atrium, hepatic and portal veins did not change significantly from control to diuretic period. TERalb equals the lymphatic return rate of albumin provided the transport mechanisms are filtrative-convective (i.e. no local back transport). Additional measurements in five pigs with proteins of different molecular size confirmed a dominating filtrative-convective transport. The increased TERalb during diuretic medication is best explained by an increased lymph drainage, which may decrease interstitial fluid pressure and thereby increase the transmural capillary pressure difference being essential for a filtrative-convective transvascular albumin transport. Increased lymph drainage may contribute to the therapeutic effect of diuretic treatment in oedema and ascites.

Myxoedema and Raynaud's phenomenon

Cold hands is a common complaint in myxoedema and were reported by 15 of 17 patients before treatment of myxoedema with 4 having Raynaud's phenomenon. An increased cold sensitivity of the digital arteries could be demonstrated during finger cooling in about half of the patients and Raynaud's phenomenon was verified in the 4 patients as digital arterial closure. The cold sensitivity decreased significantly after treatment with L-thyroxine. The increased cold sensitivity in untreated myxoedema is probably due to an increased sympathetic discharge to the hands that might disclose a predisposition for Raynaud's phenomenon.

Early detection of patients at risk of developing diabetic nephropathy. A longitudinal study of urinary albumin excretion

In an attempt to detect patients at high risk of developing diabetic nephropathy, a longitudinal study of urinary albumin excretion rate (radial immunodiffusion) was carried out in 15 female and 8 male long-term insulin-dependent diabetics without proteinuria (negative Albustix test).

Five females and 3 males had an elevated urinary albumin excretion at the time of screening, mean 115 ± 26 (sd) mg/24 h. Our upper normal range for urinary albumin excretion is ≤ 40 mg/24 h. The 5 patients with the highest albumin excretion subsequently developed persistent albuminuria, 132 → 1007 mg/24 h, P < 0.05, elevated serum creatinine, 83 → 128 μmol/l, P < 0.05, and raised blood pressure, 135/86 → 163/112 mmHg, P < 0.05. One patient developed intermittent albuminuria (positive Albustix test), while the variables in the remaining 2 patients were about the same during the 6 years observation period. Fifteen patients had a normal urinary albumin excretion, mean 17 ± 9 (sd) mg/24 h, at the time of the screening. Intermittent and persistent albuminuria developed in 2 patients, while albumin excretion, serum creatinine, and blood pressure were nearly unchanged in the remaining 13 patients after 6 years.

Our longitudinal study indicates that early detection of patients at high and low risk of developing persistent proteinuria i.e. diabetic nephropathy, is possible by using a sensitive method for measuring urinary albumin excretion.

Kidney function and size in diabetics before and during initial insulin treatment

GFR, RPF, and kidney size were measured in nine young recently diagnosed insulin-dependent diabetics before (days 0) and 3 and 8 days after the beginning of the initial insulin treatment and in comparable control subjects. Kidney function was measured by a constant infusion technique using I-125-iothalamate and 131-I-hippuran. Kidney size was determined by means of ultrasound. Before insulin treatment elevated values for GFR (+44%, P less than 0.01), RPF (+18%, P less than 0.05), and kidney size (+29%, P less than 0.01) were found. Near-normal metabolic control was achieved in all patients using either multiple subcutaneous injections of insulin or an artificial betacell. GFR decreased from 160 +/- 9 SEM to 141 +/- 6 ml/min X 1.73 m2 (P less than 0.01) and further to 133 +/- 5 ml/min X 1.73 m2 (P less than 0.01, compared to day 0). Renal plasma flow was 601 +/- 33 and 588 +/- 44 ml x 1.73 m2 at days 0 and 3, respectively (NS) and decreased to 558 +/- 35 ml/min x 1.73 m2 at day 0 (P less than 0.01). By contrast no statistically significant changes in kidney volume were observed; the results on day 0, 3 and 8 were 145 +/- 7, 162 +/- 11 and 143 +/- 9 ml/1.73 m2, respectively. The present study demonstrates that kidney size and function are elevated at the onset of insulin-dependent diabetes. Near-normal metabolic control; for 8 days induces a reduction but not a complete normalization in kidney function. From the present observations it is suggested that the rapidly reversible part of the elevation in GFR cannot be explained by concomitant changes in kidney and glomerular size (morphological origin) but is probably due to a reduction in renal plasma flow and to a decreased transglomerular pressure (functional origin).

Kidney function and size in type 1 (insulin-dependent) diabetic patients before and during growth hormone administration for one week

Kidney function and size were studied in seven well-controlled male Type 1 (insulin-dependent) diabetic patients before and after administration of highly purified human growth hormone for one week. Glomerular filtration rate, renal plasma flow (steady state infusion technique with urinary collections using 125I-iothalamate and 131I-hippuran), kidney size (ultrasonic scanning) and urinary excretion rates of albumin and beta-2-microglobulin were measured. Highly purified growth hormone was injected subcutaneously, 2 IU in the morning and 4 IU in the evening. The growth hormone dosage applied induced an elevation in plasma growth hormone concentration from the normal level seen in these very well controlled diabetics to levels within the range previously demonstrated in normally controlled Type 1 diabetic patients. During the week of growth hormone administration, glycaemic control was maintained unchanged by increasing the insulin dose by 79 +/- 9% (mean +/- SEM). Glomerular filtration rate increased from 122 +/- 3 to 131 +/- 3 ml/min X 1.73 m2 (p less than 0.05) and renal plasma flow increased from 535 +/- 10 to 569 +/- 22 ml/min x 1.73 m2 (p less than 0.05). Kidney size changed from 128 +/- 5 to 133 +/- 5 ml/1.73 m2 (NS). Urinary excretion rates of albumin and beta-2-microglobulin were unchanged. The present findings suggest that the growth hormone elevation typically found in Type 1 diabetic patients with reasonable clinical control, contributes to the enhanced glomerular filtration rate and renal plasma flow present in that disease.

Acid glycosaminoglycans in myxoedema

Acid glycosaminoglycans were measured in the tissues of a virtually untreated 83-year-old woman with myxoedema. Intercellular oedema was demonstrated histologically in the tongue, myocardium, striated muscles, and in the skin. Tissue oedema was absent in two female control patients. All tissues from the patient with myxoedema, apart from the stomach, showed high concentrations of hyaluronic acid, but there was no consistent elevation of chondroitin-4,6-sulphate, heparan sulphate or dermatan sulphate. The accumulation of hyaluronic acid might contribute to the oedema formation in myxoedema.

Hemodynamics in diabetic orthostatic hypotension

Hemodynamic variables (blood pressure, cardiac output, heart rate, plasma volume, splanchnic blood flow, and peripheral subcutaneous blood flow) and plasma concentrations of norepinephrine, epinephrine, and renin were measured in the supine position and after 30 min of quiet standing. This was done in normal subjects (n = 7) and in juvenile-onset diabetic patients without neuropathy (n = 8), with slight neuropathy (decreased beat-to-beat variation in heart rate during hyperventilation) (n = 8), and with severe neuropathy including orthostatic hypotension (n = 7). Blood pressure decreased precipitously in the standing position in the diabetics with orthostatic hypotension, whereas moderate decreases were found in the other three groups. Upon standing, heart rate rose and cardiac output and plasma volume decreased similarly in the four groups. The increases in total peripheral resistance, splanchnic vascular resistance and subcutaneous vascular resistance were all significantly lower (P less than 0.025) in the patients with orthostatic hypotension compared with the other three groups. The increase in plasma norepinephrine concentrations in the patients with orthostatic hypotension was significantly lower (P less than 0.025) than in the patients without neuropathy, whereas plasma renin responses to standing were similar in the four groups. We conclude that in diabetic hypoadrenergic orthostatic hypotension the basic pathophysiological defect is lack of ability to increase vascular resistance, probably due to impaired sympathetic activity in the autonomic nerves innervating resistance vessels; cardiac output and plasma volume responses to standing are similar to those found in normal subjects and in diabetics without neuropathy.

Kidney function and size in normal subjects before and during growth hormone administration for one week

Kidney function and size were studied in seven normal male subjects before and after administration of highly purified human growth hormone for 1 week. Glomerular filtration rate, renal plasma flow (steady-state infusion technique with urinary collections using 125I-iothalamate and 131I-hippuran) kidney size (ultrasonic scanning) and urinary excretion rates of albumin and beta 2-microglobulin (radioimmunoassays) were measured. Highly purified growth hormone was injected subcutaneously, 2 IU in the morning and 4 IU in the evening. Glomerular filtration rate increased from (mean +/- SEM) 114 +/- 5 to 125 +/- 4 ml/min x 1.73 m2 (P less than 0.01) and renal plasma flow increased from 554 +/- 30 to 601 +/- 36 ml/min x 1.73 m2 (P less than 0.01). Kidney size and urinary excretion rates of albumin and beta 2-microglobulin did not change significantly. Our results show that raising plasma growth hormone into a range similar to that found in insulin-dependent diabetics enhances glomerular filtration rate and renal plasma flow, while kidney size remains unchanged. Increased renal plasma flow is the major determinant of growth hormone induced elevation in glomerular filtration rate. Growth hormone may thus contribute to the enhancement of glomerular filtration rate and renal plasma flow typically found in insulin-dependent diabetics.

Renal function in streptozotocin-diabetic rats

Renal function was examined with micropuncture methods in the insulin-treated streptozotocin-diabetic rat. Kidney glomerular filtration rate was significantly higher in the diabetic rats (1.21 ml/min) than in the control group (0.84 ml/min) Nephron glomerular filtration rate increased in proportion to the rise in kidney glomerular filtration rate (diabetic rats: 37.0 nl/min; control rats: 27.9 nl/min). Likewise renal plasma flow was significantly higher in the diabetic rats (4.1 ml/min) than in the control group (3.0 ml/min). Glomerular capillary pressure was identical in both groups (56.0 and 56.0 mmHg, respectively). The proximal intratubular pressure was significantly reduced in the diabetic rats (10.4 mmHg; control value: 12.5 mmHg). The effective glomerular ultrafiltration coefficient was slightly but not significantly higher in the diabetic rats (0.027 nl s-1mmHg-1) than in the control group (0.023 nl s-1mmHg-1). Kidney weight was significantly higher in the diabetic rats (1.15 g; control rats: 0.96 g) while body weight was similar in both groups (diabetic rats: 232 g; control rats: 238 g). Calculations indicate that the increases in transglomerular hydraulic pressure, renal plasma flow and ultrafiltration coefficient of the glomerular membrane contribute about equally to the rise in glomerular filtration rate. The increases in the values of the determinants of glomerular filtration rate may be the result of renal hypertrophy. These studies suggest that this model provides a useful method for investigating kidney function in diabetes, which may have relevance for our understanding of the kidney abnormalities in human diabetes.

Effect of intravenous glucose infusion on renal function in normal man and in insulin-dependent diabetics

The effect of intravenous glucose infusion on glomerular filtration rate and renal plasma flow (constant infusion technique using 125I-iothalamate and 131I-hippuran) and on urinary excretion of albumin and beta-2-microglobulin were studied in ten normal subjects and seven metabolically well-controlled insulin-dependent diabetics. Following glucose infusion in normal subjects (n = 10) blood glucose increased from 4.7 +/- 0.1 to 10.9 +/- 0.4 mmol/l (SEM) (p less than or equal to 0.01). Glomerular filtration rate increased from 116 +/- 2 to 123 +/- 3 ml/mi x 1.73 m2 (p less than or equal to 0.01), while no change in renal plasma flow was seen - 552 +/- 11 versus 553 +/- 18 ml/min x 1.73 m2. Volume expansion with intravenous saline infusion in six of the normal subjects induced no changes in blood glucose or kidney function. In seven strictly controlled insulin-dependent diabetics, blood glucose values were raised from 4.6 +/- 0.4 to 16.0 +/- 0.6 mmol/l and clamped by means of an 'artificial beta cell'. Glomerular filtration rate increased in all patients, from 133 +/- 5 to 140 +/- 6 ml/min x 1.73 m2 (p less than or equal to 0.02), as did renal plasma flow from 576 +/- 26 to 623 +/- 38 ml/min x 1.73 m2 (p less than or equal to 0.02). Urinary albumin excretion remained unchanged in both normal subjects and diabetics. beta-2-microglobulin excretion rate increased significantly in the diabetics following glucose infusion, while no significant change was seen in the normal subjects. Our results show that hyperglycaemia per se contributes to the increased glomerular filtration rate and renal plasma flow in insulin-dependent diabetes.

The effect of ascitic fluid hydrostatic pressure on albumin extravasation rate in patients with cirrhosis of the liver

Overall transvascular escape rate of albumin [TERalb, i.e. the fraction of intravascular mass of albumin (IVMalb) passing to the extravascular space per unit time] was determined from the disappearance of i.v. injected radioiodinated serum albumin. Patients with tense ascites due to liver cirrhosis and pigs with posthepatic portal hypertension and intraperitoneally instilled fluid were studied before and after abdominal paracentesis in order to evaluate the effect of ascitic fluid hydrostatic pressure on the transvascular escape rate of albumin. TERalb of the ascitic patients (n = 6) were on average 7.8% IVMalb.h-1, which is somewhat higher but not significantly above normal (mean 5.6% IVMalb.h-1). After paracentesis and removal of the ascitic fluid, TERalb rose significantly to an average of 11.9% IVMalb.h-1 (P less than 0.05). The fraction of IVMalb passing into the peritoneal cavity was on average 0.21 and 0.38% IVMalb.h-1 before and after paracentesis, respectively (n = 4). In ascitic, posthepatic portal-hypertensive pigs (n = 6), TERalb averaged 15.1% IVMalb.h-1, a value not being significantly different from non-ascitic, normotensive controls (mean 16.1% IVMalb.h-1). After paracentesis, TERalb rose significantly to an average of 24.3% IVMalb.h-1. The increased albumin extravasation rate after removal of ascites is best explained by an increased sinusoidal-tissue pressure difference caused by a decreased hydrostatic fluid pressure in the liver interstitium (portal and subcapsular spaces) due to the hydrostatic effect of the removed ascitic fluid.

Reduced albuminuria during early and aggressive antihypertensive treatment of insulin-dependent diabetic patients with diabetic nephropathy

Urinary albumin excretion rate (radial immunodiffusion), glomerular filtration rate (GFR) (single-shot 51Cr-EDTA technique), and arterial blood pressure (BP) were measured in 12 juvenile-onset, insulin-dependent diabetic patients with persistent proteinuria (greater than 0.5 g/day) due to diabetic nephropathy. Mean age of the patients was 30 yr. All patients had a diastolic blood pressure greater than or equal to 95 mm Hg. Metoprolol, hydralazine, and furosemide or thiazide were used as antihypertensives. During the 12-mo treatment period, BP decreased from 151/104 to 133/85 mm Hg (P less than 0.001), the urinary albumin excretion rate diminished from 1447 to 613 micrograms/min (P less than 0.005), and GFR declined from 96 to 89 ml/in/1.73 m2 (P less than 0.01). A linear relationship between mean blood pressure and the logarithm of the albuminuria was found (r = 0.48, P less than 0.01). Arterial hypertension is an early feature of diabetic nephropathy in young insulin-dependent patients. Early and aggressive treatment of that condition decreases albuminuria, probably due to reduced intraglomerular filtration pressure. Whether sustained reduction in arterial blood pressure to near-normal levels during several years also reduces the rate of decline in GFR in diabetic nephropathy remains to be established.

Increased transvascular escape rate of albumin during experimental portal and hepatic venous hypertension in the pig. Relation to findings in patients with cirrhosis of the liver

Transvascular escape rate of albumin [TERalb, i.e. the fraction of the intravascular mass of albumin (IVMalb) passing to the extravascular space per unit time] was determined from the disappearance of i.v. injected radioiodinated serum albumin in anaesthetized pigs during control conditions and during regional venous congestion in the infradiaphragmatic area. Balloon catheters were placed in the portal vein (infrahepatic portal congestion) and in the inferior vena cava above (suprahepatic caval congestion) and below (infrahepatic caval congestion) the outlets of the hepatic veins. TERalb was on the average 13% IVMalb.h-1 under basal pressure conditions. TERalb rose significantly (p less than 0.01) during suprahepatic caval and infrahepatic portal congestion to an average of 29 and 19% IVMalb.h-1, respectively. TERalb was positively correlated to the portal pressure (r = 0.75, P less than 0.001). Only a minor increment in TERalb was found during infrahepatic caval congestion. The hepatic share of the increased TERalb during stasis above the hepatic veins was estimated to be threefold that of the extrahepatic splanchnic area. Our results point to filtration of protein, predominantely through the lining of the sinusoids and perisinusoidal space of the liver into the interstitial space around the portal vessels and further into the lymphatics, as the main mechanism of the previously demonstrated marked increase in TERalb in patients with portal venous hypertension due to cirrhosis of the liver.

Distribution and degradation of albumin in extensive skin disease

The distribution and degradation of albumin were determined in twelve patients with extensive skin disease and in ten control subjects by measuring the metabolic turnover and transcapillary escape of 132 I-labelled albumin. The ratio of intravascular to total mass of albumin was normal. Thus the observed hypoalbuminaemia and the low intravascular mass reflect a reduced mass of total body albumin. The rate of synthesis was normal, but the transcapillary escape rate reflecting the microvascular leakiness to macromolecules, and the fractional disappearance rate were significantly higher in the patients than in the controls (P less than 0.001). It is concluded that the hypoalbuminaemia in these patients is the result of an increased endogenous catabolism of albumin without significant loss via urine, stools or skin. A positive correlation between the transcapillary escape rate and fractional catabolic rate of albumin supports the concept of a causal relationship between these parameters.

Increased kidney size, glomerular filtration rate and renal plasma flow in short-term insulin-dependent diabetics

Glomerular filtration rate (GFR), renal plasma flow (RPF) and kidney volume were measured in thirteen male subjects (mean age 30 years) with short-term insulin-dependent diabetes (mean duration of disease 2.4 years) and fourteen normal male subjects (mean age 29 years). GFR and RPF were measured by constant infusion technique using I125-iothalamate and 131I-hippuran. Kidney size was determined by means of ultrasound. GFR, RPF and kidney volume were increased in the diabetic patients compared to the normal controls, 144 versus 113 ml/min X 1.73 m2 (p less than 0.0005), 627 versus 523 ml/min X 1.73 m2 (p less than 0.0025) and 278 versus 224 ml/1.73 m2 (p less than 0.0005) respectively. Combining results from diabetic patients and controls revealed a positive correlation between kidney size and GFR (r = 0.70, p less than 0.001) and between kidney size and RPF (r = 0.61, p less than 0.001). Within the groups kidney size and RPF correlated significantly in the diabetics (p less than 0.01) and the same was found for kidney size and GFR (0.025 less than p less than 0.05), while no correlations were found in the normal group. GFR and RPF correlated in the diabetics when evaluated separately (r = 0.81, p less than 0.001) and in the controls (r = 0.73, p less than 0.001). The previous and present data suggest that the mechanisms of the elevated GFR in insulin-dependent diabetics are enhanced RPF, increased transglomerular hydrostatic pressure gradient and increased glomerular ultrafiltration coefficient. The increased kidney size is probably the main cause of the above alterations in the GFR determinants.

A prospective study of glomerular filtration rate and arterial blood pressure in insulin-dependent diabetics with diabetic nephropathy

Glomerular filtration rate (GFR, single bolus 51Cr-EDTA technique), serum creatinine, proteinuria and arterial blood pressure have been measured prospectively in 14 young onset insulin-dependent diabetics selected by of persistent proteinuria (greater than 0.5 g/day) secondary to diabetic nephropathy. Twelve of the 14 patients had normal serum creatinine levels. None of the patients received antihypertensive treatment. During the mean observation period of 26 months (range 23 to 33 months) GFR decreased from 107 to 87 ml/min/1.73 m2 (p less than 0.001), serum creatinine remained unchanged: 107 and 112/mumol/l (NS), proteinuria increased from 1.8 to 3.3 g/day (p less than 0.001) and arterial blood pressure rose from 132/88 to 153/101 mmHg (p less than 0.001). Glomerular filtration rate decreased linearly with time (slope = -0.75, r = 0.99, p less than 0.001) by a mean of 0.75 ml/min/month (range 0.1 to 1.5 ml/min/month). The decrease in GFR did not correlate wih sex, age at onset, duration of diabetes, arterial blood pressure, proteinuria, insulin requirement, postprandial blood glucose or the initial GFR in each individual was constant, but varied considerably between patients. Increase in arterial blood pressure to a hypertensive level is an early feature of diabetic nephropathy in young insulin-dependent diabetics.

Plasma and interstitial fluid volume in extensive skin disease

Plasma volume and extracellular fluid volume were determined simultaneously in 17 patients with extensive skin disease and 18 matched normal subjects after an intravenous bolus injection of 131I-labeled human serum albumin and inulin. The patients had a decrease in plasma volume (-6%), which, however, was statistically significant only when related tao body weight or surface area. There was a concomitant increase in extracellular fluid volume (+7%) and interstitial fluid volume (+12%). These deviations from control data were statistically significant neither in absolute values nor when related to body size. Interstitial fluid volume was calculated as the difference between extracellular fluid volume and plasma volume. The mean plasma volume: interstitial fluid volume ratio was significantly lower in the patients (0.35 +/- 0.05 SD) than in the control group (0.42 +/0 0.05 SD) (p < 0.001). These results show that a shift of fluid from the intra- to the extracellular spaces is present in patients with extensive skin disease. Elevated microvascular water filtration in the skin is suggested as a major mechanism of this abnormal fluid distribution.

Filtration as the main transport mechanism of protein exchange between plasma and the peritoneal cavity in hepatic cirrhosis

Fractional peritoneal reabsorption rates (FPRR) were determined from the plasma activity after simultaneous intraperitoneal injection of 131I-labelled serum albumin (a) and 125I-labelled immunoglobulin G-IgG (g) in eight patients with cirrhosis (+ ascites 6, -ascites 2) and in one patient with carcinomatous ascites. Trans-vascular escape rates of albumin (TERa) and IgG (TERg) were determined in the cirrhotic patients from the disappearance of simultaneously intravenously injected 131I-labelled serum albumin and 124I-labelled IgG. Peritoneal space to plasma appearance times ranged 0.1-3.3 h, and the appearance times of albumin and IgG were almost identical. In patients with cirrhosis FPRRa and FPRRg were on average 1.27 and 1.21% of intraperitoneal protein masses returning to plasma per hour, respectively. Mean FPRRg/FPRRa ratio was 0.95 and this value was not significantly different from unity, but significantly higher (P < 0.001) than the ratio between the free diffusion coefficients of IgG and albumin (0.06). The calculated ascitic fluid flow rate was on average 61 ml/h. TERa and TERg were on average 9.6 and 8.6% of intravascular protein masses per hour, mean TERg/TERa ratio was 0.95. Peritoneal space to plasma protein flux averaged 0.4% of the intravascular protein mass per hour. The results point to filtration (convective flux) as the main transport mechanism responsible for protein passage into the peritoneal cavity as well as for the protein passage (lymphatic drainage) back into the plasma. Pressure measurements during catheterization confirmed pressure differences essential for convective flux.

The effect of glucagon infusion on kidney function in short-term insulin-dependent juvenile diabetics

Kidney function was studied in nine, metabolically well controlled, short-term insulin-dependent male diabetics before and during glucagon infusion of 4 to 5 and 8 to 10 ng/kg/min. Glomerular filtration rate, effective renal plasma flow (steady-state infusion technique, with urinary collections, using 125I-iothalamate and 131I-iodohippurate), and urinary albumin and beta 2-microglobulin excretion rates were measured. The mean plasma glucagon concentration increased during infusion from 254 +/- 19 pg/ml to 440 +/- 31 pg/ml (low dose) and 730 +/- 52 pg/ml (high dose). Glomerular filtration rate increased in all subjects from 133 +/- 5 before the glucagon infusion to 141 +/- 4 with the low dose, and 148 +/- 7 ml/min/1.73 m2 with the high dose (p < 0.01). The increase in glomerular filtration rate correlated with the rise in plasma glucagon concentration (r = 0.67; p < 0.01). Renal plasma flow increased from 530 +/- 21 before the glucagon infusion to 555 +/- 20 with the low dose and 572 +/- 29 ml/min/1.73 m2 with the high dose (p < 0.01). Urinary beta 2-microglobulin excretion rate rose from 5.8 +/- 1.0 before infusion to 8.7 +/- 1.7 with the low dose, and 17.9 +/- 5.7 micrograms X 10(-2)/min with the high dose (p < 0.01). Urinary albumin excretion remained unchanged during the glucagon infusion. These results suggest that glucagon may contribute to the reversible elevation of glomerular filtration rate typically found in poorly regulated insulin-dependent diabetics, but not to the moderate elevation found in well controlled diabetics.

Filtration as the main mechanism of increased protein extravasation in liver cirrhosis

Transvascular escape rates of albumin and immunoglobulin-G, IgG (TERalb and TERIgG, i.e, the fractions of intravascular mass of albumin and IgG passing to the extravascular space per unit time) were determined simultaneously from the disappearance of intravenously injected 131I-labelled human serum albumin and 125I-labelled human IgG in eight patients with cirrhosis of the liver. The mean wedged hepatic venous pressure was 22 mmHg (range 13-34). TERalb and and TERIgG/TERalb ratio was on average 8.4 +/- 0.8%/h (SD), and 7.4 +/- 1.9%/h (SD), respectively and these values are significantly increased compared to normal subjects [TERalb = 5.2 +/- 1.0 %/h (SD) and TERIgG = 3.0 +/- 0.7 %/h (SD), P less than 0.001]. The TERIgG/TERalb ratio was on average 0.88 +/- 0.20 (SD), which is significantly higher than that of normals [0.58 +/- 0.08 (SD), P less than 0.005]. The results indicated that increased filtration (bulk flow) is the dominant process of the increase microvascular protein escape in cirrhosis, due most likely to increased hepatic, but also to increased extrahepatic splanchnic transcapillary protein flux.

Urinary albumin and beta 2-microglobulin excretion rates in patients with systemic lupus erythematosus

The daily urinary albumin and beta 2-microglobulin excretion rates were measured with sensitive radioimmunoassays in 14 patients with systemic lupus erythematosus (SLE). The duration of SLE ranged from 0.5 to 18 years, mean 10 years. The mean age was 37 years. All patients except 5 received prednisone, 5-20 mg/day. None of the patients had proteinuria as judged by the "Albustix" test, and all had normal serum creatinine. The daily urinary albumin and beta 2-microglobulin excretion rates were nearly the same as those previously found by us in 27 adult control subjects with a mean age of 44 years. Our study shows that SLE patients without clinical proteinuria have a completely normal renal glomerular and tubular protein handling, irrespective of the duration of the disease.

Effect of metabolic regulation on renal leakiness to dextran molecules in short-term insulin-dependent diabetics

Renal clearance of dextran of two ranges of molecular size and glomerular filtration rate (GFR, 51Cr-EDTA) were measured in seven short-term insulin-dependent diabetics (mean age 25 years). Measurements were carried out in the same patient during good and poor metabolic regulation (plasma glucose, mean +/- SEM, 6.5 +/- 0.9 and 14.8 +/- 1.5 mmol/l, respectively). GFR was elevated in all patients during poor metabolic regulation (119 +/- 6 ml/min/1.73 m2, versus 99 +/- 2 ml/min/1.73 m2 during good control, p less than 0.01). The average renal clearance of dextran with molecular weights ranging from 25,000 to 35,000 and 35,000 to 45,000 increased during poor metabolic regulation from 14.8 +/- 0.8 to 19.8 +/- 1.8 ml/min/1.73 m2, and 5.2 +/- 0.3 to 6.8 +/- 0.6 ml/min/1.73 m2, respectively (p less than 0.05). The elevated GFR and renal dextran clearance found during poor metabolic regulation were normalized within one to three weeks of effective insulin treatment. This rapid reversibility can hardly be explained by the previously demonstrated enlargement in glomerular size and filtration surface area, since these alterations remain unchanged after more than one month of insulin treatment. The metabolic regulation did not influence the size-selective properties of the glomerular wall. Therefore, we suggest that the dominating mechanism involved in the GFR and renal dextran clearance alterations is functional, viz. increased filtration pressure.

Mechanisms of edema formation in myxedema--increased protein extravasation and relatively slow lymphatic drainage

We assessed extravascular accumulation of albumin and fluid in primary myxedema by measuring metabolic turnover and transcapillary escape of 131I-labeled human albumin in seven patients. In the hypothyroid state, we found a low plasma volume (P less than 0.05), a reduced rate of albumin synthesis and catabolism (P less than 0.01), an increased transcapillary escape rate of albumin (P less than 0.01), a remarkable increase in the extravascular mass of albumin (1500 micronmol; P less than 0.01) and a longer mean transit time through the extravascular spaces in primary myxedema than in other states of generalized edema (P less than 0.05). All variables returned to normal during l-thyroxine treatment. The extravascular accumulation of albumin, and presumably of all other plasma proteins, is important in the generalized edema typically found in myxedema. Inadequate lymphatic drainage may also explain the formation of exudates in the serous cavities that are well known in myxedema.

Intravenous insulin has no effect on transcapillary escape rate of albumin and on plasma volume in short-term juvenile diabetics

The permeability of the microvasculature was studied for the first 50 min after an intravenous injection of between 6 and 10 U of crystalline insulin in seven juvenile diabetics whose mean age was 22 yr. No patient had clinical signs of neuropathy or microangiopathy. The following variables were determined before and after the insulin injection: plasma volume, PV (125I-labeled and 131I-labeled human serum albumin), plasma protein concentration, hematocrit, blood pressure, and pulse rate. PV was measured 40, 45, and 50 min after the insulin injection. Transcapillary escape rate of albumin (TER), defined as the fraction of intravascular mass of albumin that passes to the extravascular space per unit of time, was determined after insulin from the disappearance of the intravenously injected 125I-labeled human serum albumin. The mean blood glucose concentration decreased from 15.1 to 10.8 mmol/L at 50 min after the insulin injection. Blood pressure remained unchanged, while a significant increase in pulse rate occurred after the insulin administration. A reduction in PV, calculated after a mixing period lasting 10 (−3.9%), 15 (−2.3%), and 20 (−1.7%) min, was found after the insulin injection. The last-mentioned difference is not significant statistically. The venous hematocrit remained unchanged; this variable was measured so accurately that a 1% decrease in plasma volume could be excluded with 99% confidence. Plasma protein concentration also remained unchanged. Except the one patient with an extremely high TER (10.6%/h), the remaining six patients had normal TER values after the insulin injection (mean, 5.8; range, 4.5–7.2%/h) compared with our previously investigated control group (mean, 5.4; range, 3.8–7.2%/h) and a comparable group of six short-term juvenile diabetics investigated during good (mean, 5.8; range, 4.4–7.2%/h) and poor (mean, 6.9; range, 5.7–7.7%/h) metabolic regulation (these patients did not receive insulin before the TER determination). In agreement with a previous study, thus, we found a significant reduction in plasma volume and in intravascular mass of protein after a small dose of crystalline insulin intravenously. But the present finding of an unchanged hematocrit and a normal TER does not support the suggestion made in the previous study, viz. that there is an increased transfer of fluid and albumin out of the vascular system. The most likely explanation for the abovementioned reductions is bad mixing (pooling), probably a result of the insulin-induced increase in adrenergic nervous activity, causing vasoconstriction and reduced peripheral blood flow, as demonstrated previously.

Kidney function in normal man during short-term growth hormone infusion

Kidney function was studied in 9 normal males before and during a 2 h growth hormone (GH) infusion of 50 ng/kg/min. The following variables were measured during each 20 min clearance period: glomerular filtration rate, GFR, effective renal plasma flow, RPF (steady state infusion technique with urinary collections using [125I]iothalamate and [131I]iodohippurate), and urinary albumin and beta2-microglobulin excretion rates (radioimmunoassays). The GH infusion resulted in a 10-fold increase in plasma GH concentration. All the above mentioned variables remained practically unchanged during the infusion except for a small (-5%) but significant decrease in renal plasma flow (P less than 0.01). Our negative results contrast to the findings of increased GFR and RPF during prolonged GH administration and suggest that GH requires several hours or days for its renal effects to become manifest.

Extracellular fluid volume determined by a single injection of inulin in men with untreated essential hypertension

The extracellular volume (ECV) and plasma volume (PV) were determined simultaneously in nine men with untreated essential hypertension and in nine healthy matched control subjects, using a single injection of inulin and of 131I-labelled human serum albumin, respectively. The average mean arterial blood pressure in the hypertensive group was 178/118 mmHg. ECV was nearly the same in the two groups, viz. 151 ml/kg body weight (SD 17) in the hypertensive group compared to 147 ml/kg (SD 16) in the control group. The corresponding figures for PV were 38.2 ml/kg body weight (SD 4.7) and 43.7 ml/kg (SD 7.9) respectively (P less than 0.1). The calculated interstitial fluid volume (IV) was 113 ml/kg (SD 16) and 103 ml/kg (SD 10) (P less than 0.2). The PV/IV ratio was significantly lower (P less than 0.02) in the hypertensive group (0.34, SD 0.06) than in the normal group (0.42, SD 0.06). The difference might suggest increased transcapillary water filtration in hypertension.

Increased transcapillary escape rate of albumin in patients with cirrhosis of the liver

The transcapillary escape rate of albumin (TERalb), i.e. the fraction of intravascular mass of albumin that passes to the extravascular space per unit time, was determined from the disappearance of intravenously injected 125I-labelled human serum albumin during the first 60 min after injection in nine patients with cirrhosis of the liver. Six of the patients had ascites. The wedged hepatic venous pressure or splenic pulp pressure ranged from 20 to 30 mmHg, mean 26 mmHg. Plasma albumin concentration was low, but plasma volume was slightly enlarged, and thus the intravascular mass of albumin was only moderately reduced. The transcapillary escape rate of albumin was significantly elevated in all the cirrhotics, mean 10.2%/h, range 8.8 to 12.3%/h, in comparison to values for twenty-eight normal subjects 5.4%/h, range 3.5-7.2%/h. Our results can best be explained by increased filtration out of the vessels in the portal system, due to the increased portal venous pressure. The increased TERalb probably contributes to the formation of oedema and ascitic fluid.

Trisomy 8 syndrome. A psychological and somatic study of a mentally non-retarded male with 46,XY/47,XY,+8 chromosome constitution

A 27-year-old, non-retarded male with trisomy 8 mosaicism (46,XY/47,XY,+8) had a short head, a short broad-bridged nose, a protruding upper lip, pterygium colli, moderate kypho-scoliosis, camptodactyly of all fingers and deep furrowing on the soles. Radiographic examination of columna showed spina bifida of L1 and fusion of L5 and S1. These findings are characteristic for the trisomy 8 syndrome. A psychological study showed a personality characterized by immaturity and lack of spontaneity and self-confidence. An intelligence test (WAIS) placed him within the normal range, but presented an uneven development of the cognitive functions with special difficulties in synthetic abilities and visual scanning. His auditive span was rather low, and his memory functions were somewhat below average.

The effect of short-term glucagon infusion on kidney function in normal man

Kidney function was studied in six normal males before and during a 2 h glucagon (10 ng/kg/min) infusion. The following variables were determined during each 20 min clearance period; glomerular filtration rate (GFR), renal plasma-flow (RPF) , filtration fraction (FF), urinary albumin and beta2-microglobulin-excretion rates. Glucagon infusion resulted in a fourfold increase in plasma glucagon concentration. The infusion induced a significant increase in GFR (+9%), FF (+9%) and urinary beta2-microglobulin excretion rate (+32%), (p less than 0.01). RPF and urinary albumin excretion rates were not significantly changed. We suggest that glucagon may contribute to the reversible kidney function alterations typically found in poorly regulated juvenile diabetes, a state with relative or absolute hyperglucagonaemia.

Increased transcapillary escape rate of albumin and IgG in essential hypertension

Transcapillary escape rates of albumin and IgG (fractions of intravascular mass of albumin and IgG that pass to the extravascular space per unit time) were determined simultaneously from the initial disappearance of intravenously injected 131I human albumin and 125I human IgG in seven untreated subjects suffering from essential hypertension. The average mean arterial blood pressure of these subjects 193/119 mmHg; four subjects had grade I-III funduscopic changes. Transcapillary escape rates of albumin (TERalb) and IgG (TERIgG) were found significantly increased in the hypertensive subjects, average 7.8 +/- 0.9 (SD) and 4.7 +/- 1.0 (SD) %/h, respectively, compared with normal values of mean 5.2 +/- 1.0 (SD) and 3.0 +/- 0.7 (SD) %/h, respectively (P less than 0.01). There was a statistically significant positive correlation between the mean arterial blood pressure and TER of albumin and of IgG (P less than 0.001). The TERIgG/TERalb ratio was about the same in the hypertensives and the normals. Confirming a previous observation, we found an increase in the daily urinary albumin excretion rate from a normal average of 9.1 (range, 2.4-20.4)mg/24 h to 96 (range, 5.6-565) mg/24 h, P less than 0.05. The present findings can best be explained by increased filtration through normal pores between the endothelial cells in the microvasculature, due to the high arterial blood pressure.

Plasma volume, intravascular albumin and its transcapillary escape rate in patients with extensive skin disease

Plasma volume and plasma concentration and transcapillary escape rate of albumin (TER alb), i.e. the fraction of intravascular mass of albumin that passes to the extravascular space per unit time, were determined using 125I-labelled human albumin in eight patients with extensive skin disease. Plasma volume and plasma albumin concentration were reduced (P less than 0-05). Thus the intravascular albumin mass was moderately decreased to an average of 0-55 +/- 0-06 (s.d.) g/cm height compared with a normal mean value of 0-77 +/- 0-07 (s.d.) g/cm. This 29% decrease is statistically significant (P less than 0-001). The transcapillary escape rate of albumin (TER alb) was significantly elevated, mean 8-6 +/- 1-1 (s.d.) % X h-1, as compared to normal subjects, mean 5-6 +/- 1-1 (s.d.) % X h-1, (+54%, P less than 0-001). The same patients were studied again after a 1-week treatment with prednisone, 25-60 mg per day. Plasma albumin concentration, plasma volume and intravascular mass of albumin were unchanged, while TER alb decreased significantly during treatment, mean 5-9 +/- 0-8 (s.d.) % X h-1, (P less than 0-01). It is suggested that displacement of albumin into the skin and loss of albumin from the skin are the dominating mechanisms of the reduction in the intravascular albumin mass in patients with extensive skin disease.

Transcapillary escape rate of albumin and right atrial pressure in chronic congestive heart failure before and after treatment

The transcapillary escape rate of albumin (TERalb), i.e., the fraction of intravascular mass of albumin that passes to the extravascular space per unit of time, was determined from the disappearance of intravenously injected 125I-labeled human serum albumin during the first 60 minutes after injection in 10 subjects with chronic right heart failure. The investigation was repeated after sodium and water depletion. Before treatment TERalb was significantly elevated (mean 8.3 +/- 1.6% (SD)/hour, in comparison to values for normal subjects (mean 5.4 +/- 1.1%/hour, P less than 0.001). With treatment TERalb decreased significantly (mean 5.9 +/- 1.2%/hour, P less than 0.01). Right atrial pressure decreased from an average of 10 mm Hg to 6 mm Hg during treatment. A statistically significant, positive correlation was found between TERalb and right atrial pressure (r = 0.77, P less than 0.001). Our results best can be explained by increased filtration, mainly through the venous end of the microvasculature, due to the increased venous pressure in heart failure.

The effect of metabolic regulation on microvascular permeability to small and large molecules in short-term juvenile diabetics

The microvascular permeability to small and large molecules was studied during good and poor metabolic regulation in ten short duration juvenile diabetics. The following variables were measured; daily urinary albumin and beta2-microglobulin-excretion rates, whole body transcapillary escape rate of albumin (TER), glomerular filtration rate (GFR), capillary filtration coefficient (CFC), and capillary diffusion capacity (CDC). The urinary albumin and beta2-microglobulin concentration were measured by sensitive radioimmunoassays; TER was detemined from the initial disappearance of intravenously injected 125I-labelled human serum albumin; GFR was measured on the forearm by straingauge plethysmography and CDS for 51Cr-EDTA clearance; CFC was measured on the forearm by straingauge plethysmography and CDC, for 51Cr-EDTA was determined in the jyperaemic anterio tibial muscle by the local clearance technique. All the above mentioned variables, except CDC, were significantly increased during poor metabolic regulation, indicating a functional microangiopathy. The mechanisms of these alterations appear to be increased filtration pressure in the microcirculation and/or increased porosity of the microvasculature. The findings of increased microvascular albumin passage are compatible with the hypothesis that the organic - histologicallly demonstrated - diabetic microangiopathy is a long-term effect of periods of increased extravasation of plasma proteins, with subsequent protein deposition in the microvascular wall, i.e. the concept to plasmatic vasculosis.

Increased microvascular permeability to plasma proteins in short- and long-term juvenile diabetics

The present findings of increased microvascular protein passage are compatible with the hypothesis that the organic, histologically demonstrated diabetic microangiopathy is a long-term effect of periods of increased extravasation of plasma proteins, with subsequent protein deposition in the microvascular wall, i.e., the concept of plasmatic vasculosis. Arterial hypertension, frequently present in diabetes, enhances the development of arteriolar hyalinosis. Effective treatment of diabetes and hypertension arrests development of the microvascular lesions.

Increased metabolic turnover rate and transcapillary escape rate of albumin in long-term juvenile diabetics

The metabolic turnover rate and transcapillary escape rate of albumin were studied with 131I-labelled human albumin in nine patients with long-term diabetes mellitus. Retinopathy was present in all patients and nephropathy in four. Plasma albumin concentration and plasma volume were reduced (P smaller than 0.05). The previously reported decrease in the intravascular albumin mass in long-term diabetics was thus confirmed by an average of 59.0 g/m2 surface area, compared with a normal value of 71.7 g/m2-(minus18%) (P smaller than 0.005). The albumin metabolic rate was increased, the fractional disappearance rate being an average 13.2% of the intravascular albumin mass per 24 hr, compared with a normal value of 8.4% (+ 57%) (P smaller 0.001). The rate of synthesis was 7.7 g - 24 h-1 - m-2 in contrast to a normal rate of 6.2 g - 24 h-1 - m-2 (+24%) (P smaller 0.001). Total body albumin mass was decreased proportionally to the intravascular mass. Confirming previous observations, we found an increase in the transcapillary escape rate of albumin (fraction of intravascular albumin mass passing to the extravascular space per unit time) from a normal average of 5.6% - hr-1 to 7.4% - hr-1 (+32%) (P ssmaller than 0.001). This finding can best be explained by an increased microvascular permeability to plasma proteins. A positive correlation between the transcapillary escape rate and fractional disappearance rate of albumin was demonstrated ( r equals 0.74; P smaller than 0.01). This supports the concept that albumin is catabolized in connection with its permeation through the microvascular endothelium.

Increased metabolic turnover rate and transcapillary escape rate of albumin in essential hypertension

The metabolic turnover rate and the transcapillary escape rate of albumin were studied using 131 I-labeled human albumin in nine untreated subjects suffering from essential hypertension. The average mean arterial blood pressure of these subjects was 162/109 mm Hg; seven subjects had grade I-II funduscopic changes. Plasma albumin concentration was normal, but plasma volume was reduced ( P < 0.05) in these subjects. Thus, the previously reported moderate decrease in the intravascular albumin mass of hypertensive subjects was confirmed; the average value for intravascular albumin mass in the present study was 62.8 g/m2 surface area compared with a normal value of 70.6 g/m 2 (-11%, P < 0.05). A surprising finding was a marked enhancement of albumin metabolic rate in essential hypertension. The fraction of intravascular albumin mass metabolized per 24-hour period was on the average 14.4% compared with a normal value of 8.4% (+72%, P < 0.001). The rate of synthesis was 9.1 g/24 hours m -2 compared with a normal value of 5.9 g/24 hours m -2 (+54%, P < 0.001). Total body albumin mass was decreased proportionally to intravascular albumin mass. Confirming a previous observation, we found an increase in the transcapillary escape rate of albumin (fraction of intravascular mass passing to the extravascular space per unit time) from a normal average of 5.6%/hour to 7.5%/hour (+34%, P < 0.001). There was a statistically significant positive correlation between the transcapillary escape rate of albumin and blood pressure ( P < 0.05). These findings can best be explained by increased filtration due to the high arterial blood pressure. There was also a positive correlation between the transcapillary escape rate and the fractional catabolic rate of albumin ( P < 0.05). This finding supports the concept that albumin is catabolized in connection with its permeation through the capillary endothelium.