Age-related change in plasma concentration of 7B2 (a novel pituitary polypeptide) in normal humans

Using a specific radioimmunoassay, we measured concentrations of plasma 7B2 (a novel pituitary polypeptide) immunoreactivity (7B2-IR) in normal human subjects, patients with chronic renal failure and those with liver cirrhosis. Mean (+/- SEM) values of plasma 7B2-IR in normal healthy men and women were 55.8 +/- 1.2 pg/ml (n = 266) and 56.1 +/- 0.9 pg/ml (n = 408), respectively. The elevation of plasma 7B2-IR showed a relationship with age of the subjects, in both men (r = 0.39, t = 6.86, p less than 0.001) and women (r = 0.35, t = 7.44, p less than 0.001). Plasma 7B2-IR concentrations were elevated in patients with chronic renal failure (536 +/- 45 pg/ml, Mean +/- SEM, n = 10) as well as those in liver cirrhosis (95 +/- 10 pg/ml, Mean +/- SEM, n = 15) compared to values in normal subjects, suggesting that 7B2 is mainly eliminated through the kidney and is partly metabolized in the liver.     

Evidence for a novel pituitary protein (7B2) in human brain, cerebrospinal fluid and plasma: brain concentrations in controls and patients with Alzheimer's disease

A novel pituitary protein, designated as 7B2, recently purified in our laboratory was measured using a specific radioimmunoassay in conjunction with immuno-affinity extraction, in cerebrospinal fluid (CSF) and in plasma obtained from normal volunteers. The mean concentrations of immunoreactive (IR)-7B2 were 2154 pg/ml in CSF and 29 pg/ml in plasma. Studies by SDS-poly-acrylamide gel electrophoresis revealed that both CSF IR-7B2 and plasma IR-7B2 have an apparent molecular weight of around 20,000-21,000 as previously observed in various rat tissues. IR-7B2 was also measured in various brain regions obtained from control subjects and patients with Alzheimer's disease. IR-7B2 was widely distributed in the human brain, with the highest concentrations in substantia nigra and caudate. IR-7B2 brain concentrations were found to be similar between control subjects and patients with Alzheimer's disease. Gel permeation chromatography of extracts of various brain regions revealed two major peaks with apparent molecular weights of 45,000-50,000 and 11,000-16,000 in hypothalamus, caudate, frontal cortex, hippocampus, putamen and locus coeruleus, and only one peak with an apparent molecular weight of 14,000-16,000 in substantia nigra and globus pallidus. These data suggest that this novel pituitary protein may play a role of consequence perhaps as a neurotransmitter or as a neuromodulator in the human central nervous system.     

Secretory protein 7B2. A novel tumor marker of medullary carcinoma of the thyroid

Mean plasma concentrations of 7B2 in three patients with medullary carcinoma of the thyroid (MCT) (294 +/- 38 pg/ml) were significantly higher than those in age-matched normal subjects (107.2 +/- 7.2 pg/ml, n = 11). The intravenous infusions of pentagastrin (0.5 microgram/kg) markedly increased the plasma concentrations of 7B2 as well as calcitonin in all three MCT patients but it caused no significant rise of the plasma 7B2 concentration in any healthy subjects. The peak times and rates of increase of plasma 7B2 concentrations were different from those of plasma calcitonin concentrations in MCT patients. The plasma 7B2 concentration in one of the patients with MCT showed a marked reduction and no further elevation from the pentagastrin infusion following a total thyroidectomy (preop. 226 pg/ml; postop. 112.1 pg/ml). The above evidence suggests that the increased levels of plasma 7B2 in MCT patients may be attributed to the release from parafollicular cells of thyroid. Therefore, 7B2 is considered to be clinically useful as a tumor marker of MCT.     

Plasma concentrations of endothelin in patients with abnormal vascular reactivity. Effects of ergometric exercise and acute saline loading

We measured circulating concentrations of endothelin, a recently discovered vasoconstrictor peptide produced by vascular endothelial cells, in healthy subjects and in patients with abnormal vascular reactivity. Endothelin concentrations were determined by radio-immunoassay after extraction of plasma using Sep-Pak C-18 cartridges in healthy subjects (n = 20), in patients with diabetes mellitus type I (n = 10), in patients with mild to moderate essential hypertension (n = 12) and in non-dialyzed patients with stable chronic renal failure (n = 12). Plasma concentrations were similar in healthy controls, in diabetics and in hypertensive patients averaging 5.0 +/- 0.6 pg/ml, 4.7 +/- 0.2 pg/ml and 6.5 +/- 1.0 pg/ml, respectively. In contrast, plasma concentrations of endothelin were markedly elevated in patients with chronic renal failure averaging 16.6 +/- 2.9 pg/ml (p less than 0.005). No correlations were observed between serum creatinine concentrations ranging from 124 to 850 mumol/l or blood pressure and plasma concentrations of endothelin. Bicycle ergometric exercise in six healthy subjects and an acute modest i.v. saline load of 1,000 ml of 0.45% NaCl administered within 60 min in six patients with mild essential hypertension did not affect plasma concentrations of endothelin. Thus, it is unlikely that vascular synthesis of endothelin is related to acute physiological changes in systemic hemodynamics or to the circulatory and renal responses to acute extracellular fluid volume (ECFV) expansion. A potential role of endothelin, however, in the control of regional blood flow cannot be excluded. Elevated plasma concentrations of endothelin observed in patients with chronic renal failure require further investigations.     

Effects of hydrocortisone and aminophylline on plasma leukotriene C4 levels in patients during an asthmatic attack

To study the role of leukotriene C4(LTC4) and the effect of hydrocortisone and aminophylline on plasma LTC4 levels in patients with asthmatic attacks, we measured LTC4 in plasma of 18 asthmatics during a wheezing attack and of 7 normal subjects. Blood samples were obtained before and after treatment with aminophylline and/or hydrocortisone injections. We extracted LTC4 using a Sep-Pak C18 cartridge for the measurement of LTC4 by radioimmunoassay. The plasma levels of immunoreactive LTC4 (i-LTC4) of the normal subjects were 142 +/- 25 pg/ml (n = 7), while those of nonatopic type asthmatic patients with wheezing attacks were 208 +/- 68 pg/ml (n = 15) (p less than 0.01). Before and after treatment with both hydrocortisone succinate (100 mg) and aminophylline (250 mg), 6 asthmatic patients with wheezing attacks had a mean plasma level of i-LTC4 181 +/- 24 and 132 +/- 18 pg/ml (p less than 0.01), respectively. On the other hand, the treatment with aminophylline 250 mg alone increased the i-LTC4 levels from 178 +/- 19 pg/mg to 213 +/- 16 pg/mg (n = 6)(p less than 0.05), while treatment with hydrocortisone succinate 100 mg decreased the i-LTC4 level 0.05 from 284 +/- 99 pg/ml to 249 +/- 85 pg/ml (n = 4)(p less than 0.05). In conclusion, the present study shows that the i-LTC4 level in venous blood of patients with asthmatic attacks is decreased significantly by treatment with hydrocortisone succinate.     

Changes in the plasma and urine alpha human atrial natriuretic peptide (alpha hANP) concentration in patients with thyroid disorders

In order to assess the possible involvement of thyroid hormone in alpha human atrial natriuretic peptide (alpha hANP), we investigated the plasma and urine ANP concentration in patients with primary hyperthyroidism and hypothyroidism. Plasma and urine were extracted through Sep-Pak C18 cartridges and the urine ANP concentration was corrected by urine creatinine (cre. mg/dl) and expressed as fmol/mg.cre.. The plasma ANP concentration in patients with untreated hyperthyroidism (32.3 +/- 7.0 fmol/ml; n = 22) was higher than in normal subjects (p less than 0.01 vs control; 6.2 +/- 0.7 fmol/ml). After restoration to euthyroidism, the plasma ANP concentration (patients with treated hyperthyroidism) fell to normal (8.9 +/- 1.9 fmol/ml). The plasma ANP concentration in patients with untreated hypothyroidism (14.1 +/- 3.0 fmol/ml; n = 7) was higher than normal, but in two of them there was mild renal dysfunction and an incomplete right blundle branch block in the electrocardiogram. It was possible that these factors contributed to the observed increase in plasma ANP. However, a significant positive correlation was found between plasma ANP and free thyroxine (n = 40, r = 0.449; p less than 0.01) and free triiodothyronine (n = 40, r = 0.546; p less than 0.01). The urine ANP concentration in patients with untreated hyperthyroidism was markedly higher than in normal subjects (p less than 0.01), but in untreated hypothyroidism not significantly different from normal.     

Plasma thromboxane and prostacyclin: comparison during normal pregnancy and pregnancy complicated by hypertension

Plasma levels of thromboxane B2 (TXB2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), stable metabolites of two prostanoids with opposing biological effects, TXA2 and prostacyclin, were measured by radioimmunoassay in normal pregnancy (controls) and pregnancy complicated by hypertension (PIH) from 32 to 36 (Period 1; P1) and from 36 to 40 (Period 2; P2) weeks of gestation. The plasma concentration of each compound in the control subjects was 265.6 +/- 58.4 (TXB2), 132.4 +/- 16.5 (6-keto-PGF1 alpha) for P1 (n = 10) and 142.6 +/- 11.8 (TXB2), 68.5 +/- 5.2 (6-keto-PGF1 alpha) for P2 (n = 10) respectively (pg/ml, mean +/- s.e). In the patients with PIH, TXB2 concentrations increased moderately for P1 (419.2 +/- 21.2; n = 7) and significantly (p less than 0.005) for P2 (452.8 +/- 31.0; n = 7) respectively (pg/ml, mean +/- s.e), while the plasma levels of 6-keto-PGF1 alpha revealed a slight to moderate decrease both for P1 (84.5 +/- 4.0; n = 7) and P2 (59.7 +/- 8.1; n = 7) respectively (pg/ml, mean +/- s.e). The physiological balance of TXB2 to 6-keto-PGF1 alpha was significantly greater (p less than 0.005) in the patients with PIH, where the TXB2/6-keto-PGF1 alpha ratio was 5.2 +/- 0.7 for P1 and 9.4 +/- 2.3 for P2 respectively (mean +/- s.e) compared with that of the controls, where it was 2.4 +/- 0.4 for P1 and 2.0 +/- 0.2 for P2 respectively (mean +/- s.e).(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of ovine corticotropin-releasing hormone and FK 33-824 (met-enkephalin analogue) on the secretions of proopiomelanocortin-derived N-terminal peptide, beta-lipotropin, beta-endorphin and adrenocorticotropin in patients with Addison's disease

The responses of plasma immunoreactive (IR) proopiomelanocortin (POMC)-derived N-terminal peptide (Nt), IR-beta-endorphin (Ep), IR-beta-lipotropin (LPH) and IR-ACTH levels to ovine corticotropin-releasing hormone (CRF) and FK 33-824 (Met-Enkephalin analogue) were studied in nine patients with Addison's disease. The basal plasma levels (mean +/- SE) of IR-Nt, IR-Ep, IR-LPH and IR-ACTH were significantly higher in patients with Addison's disease (4459 +/- 975 pg/ml, 132 +/- 25 pg/ml, 4425 +/- 1030 pg/ml, 553 +/- 89 pg/ml, respectively) than in the normal controls (202 +/- 38 pg/ml, 7 +/- 2 pg/ml, 101 +/- 18 pfi/ml, 53 +/- 16 pg/ml, respectively). Ovine CRF produced rapid and concomitant increases in plasma levels of IR-Nt, IR-Ep, IR-LPH and IR-ACTH. Ep and ACTH levels reached a peak at 30 min. On the other hand, Nt and LPH levels reached a peak at 60 min and these levels gradually decreased up to 120 min. The molar concentrations of these IR-peptides in plasma were changed in close parallel fashion to one another. FK 33-824 produced a pronounced and concomitant fall in IR-Nt, IR-EP, IR-LPH, and IR-ACTH levels. These results support the theory that Nt, Ep, LPH and ACTH are produced simultaneously from POMC as a common precursor in the pituitary gland and are secreted concomitantly under various conditions such as stimulation by CRF and inhibition by FK 33-824 in patients with Addison's disease.     

Tumor necrosis factor alpha production as a possible predictor of relapse in patients with multiple sclerosis.

No biological parameter is currently available as a specific marker of multiple sclerosis (MS) activity. The aim of this study was to determine whether an evolution of the neurological disability is associated with a modified profile of cytokine production. Clinical disease activity was quantitated by the Kurtzke's expanded disability status scale (EDSS). Whole blood was stimulated with phytohemagglutinin (PHA) for 2 hours at 37 degrees C and the activated plasma was assayed for Tumor necrosis factor alpha (TNF-alpha) and Interleukin-1 beta (IL-1 beta). Relapsing-remitting MS patients enduring a relapse (RRMS, in relapse) (721 +/- 58 pg/ml, n = 27) and chronic progressive MS (CPMS) patients (516 +/- 33 pg/ml, n = 17) had an higher TNF-alpha production capacity as compared to healthy subjects (143 +/- 25 pg/ml, n = 17), RRMS, stable patients, (123 +/- 11 pg/ml, n = 26) or other neurological diseases (OND) without immunological or inflammatory disease in the peripheral immune compartment (131 +/- 24 pg/ml, n = 14) (t test: p < 0.0001). IL-1 beta production was also significantly higher but to a lesser extent in the same conditions. Concentration of TNF-alpha was also found to be significantly higher in the cerebrospinal fluid (CSF) of CPMS patients (199 +/- 7.8 pg/ml, n = 7, p < 0.0001) but also in RRMS, in relapse (149 +/- 5.7 pg/ml, n = 11, p < 0.05) as compared to RRMS, stable (130 +/- 4.4 pg/ml, n = 7) or OND without inflammatory or immunological disease of the central nervous system (CNS) (142 +/- 6.2 pg/ml, n = 8).(ABSTRACT TRUNCATED AT 250 WORDS)     

High plasma cholecystokinin response following ingestion of test meal by patients with non-insulin dependent diabetes mellitus

Postprandial responses of plasma cholecystokinin (CCK) in patients with non-insulin dependent diabetes mellitus (NIDDM) were studied with a CCK specific radioimmunoassay. After the ingestion of a liquid test meal, plasma CCK levels increased from the basal level of 9.8 +/- 1.1 pg/ml to a peak of 19.4 +/- 1.8 pg/ml at 20 min in healthy subjects (n = 10). The ingestion of a test meal in patients with NIDDM (n = 10) resulted in a significantly greater increase of plasma CCK than in healthy subjects and a significant increase of plasma CCK from a basal level of 14.2 +/- 4.4 pg/ml to a peak of 47.4 +/- 12.4 pg/ml at 10 min.     

Elevation of plasma 7B2 (a novel pituitary protein) in cord blood at obstetrical delivery and the possible correlation with GH

Plasma 7B2-immunoreactivity (7B2-IR) concentrations in umbilical artery (UA), umbilical vein (UV) and maternal vein (MV) were measured by RIA at the time of obstetrical delivery at term. Plasma 7B2-IR concentrations (Mean +/- SEM) in UA (N = 12), UV (N = 16) and MV (N = 16) were 725 +/- 69, 699 +/- 64 and 116 +/- 4.5 pg/ml, respectively. Plasma 7B2-IR concentrations in UA and UV were much higher than those in MV. There was no arterio-venous gradient between UA and UV. A trace amount of 7B2-IR (Mean +/- SEM, 226 +/- 16.8 pg/g tissue) was detected in the placental extracts. A statistically significant positive correlation (r = 0.7595, p less than 0.005) was found between plasma 7B2-IR and GH in the UV. Significant negative correlations between body weight of the neonates and plasma levels of GH (r = -0.6836, p less than 0.01) and 7B2-IR (r = -0.4939, p less than 0.05) were also apparent. When analyzing cord blood plasma using gel permeation chromatography and SDS-polyacrylamide gel electrophoresis, a major peak with an apparent molecular weight of 20,000 was observed. These findings suggest that 7B2-IR in UA and UV originates from the fetus and that 7B2-IR does not permeate through the placenta. The possibility of involvement of 7B2 in fetal growth warrants attention.     

Diurnal rhythm of plasma immunoreactive corticotropin-releasing factor in normal subjects

Plasma corticotropin-releasing factor (CRF), corticotropin (ACTH) and cortisol levels were simultaneously determined by radioimmunoassays at 0600 h, 1200 h, 1800 h and 2200 h in six normal subjects, in order to examine whether the diurnal rhythm in plasma CRF exists and how it correlates to the diurnal rhythm in plasma ACTH and cortisol concentration. The highest CRF level was observed at 0600 h (7.0 +/- 1.2 pg/ml) and significantly lower levels (p less than 0.01) at 1800 h (1.7 +/- 0.2 pg/ml) and 2200 h (1.9 +/- 0.4 pg/ml). A clear diurnal rhythm was demonstrated in plasma ACTH and cortisol levels, with the highest values at 0600 h (44.6 +/- 8.1 pg/ml and 15.9 +/- 2.0 micrograms/dl, respectively) and the lowest at 2200 h (12.3 +/- 2.8 pg/ml and 4.6 +/- 1.0 micrograms/ml, respectively). These results suggest that the diurnal rhythm in ACTH and cortisol is under the regulation, at least in part, of the diurnal rhythm in CRF secretion.     

Effects of supine,prone, and lateral positions on cardiovascular and renal variables in humans

The hypothesis was tested that changing the direction of the transverse gravitational stress in horizontal humans modulates cardiovascular and renal variables. On different study days, 14 healthy males were placed for 6 h in either the horizontal supine or prone position following 3 h of being supine. Eight of the subjects were in addition investigated in the horizontal left lateral position. Compared with supine, the prone position slightly increased free water clearance (349 +/- 38 vs. 447 +/- 39 ml/6 h, P = 0.05) and urine output (1,387 +/- 55 vs. 1,533 +/- 52 ml/6 h, P = 0.06) with no statistically significant effect on renal sodium excretion (69 +/- 3 vs. 76 +/- 5 mmol/6 h, P = 0.21). Mean arterial pressure and left atrial diameter were similar comparing effects of supine with prone. The prone position induced an increase in heart rate (54 +/- 2 to 58 +/- 2 beats/min, P < 0.05), total peripheral vascular resistance (13 +/- 1 to 16 +/- 1 mmHg. min(-1). l(-1), P < 0.05), forearm venous plasma concentration of norepinephrine (97 +/- 9 to 123 +/- 16 pg/ml, P < 0.05), and atrial natriuretic peptide (49 +/- 4 to 79 +/- 12 pg/ml, P < 0.05), whereas stroke volume decreased (122 +/- 5 to 102 +/- 3 ml, P < 0.05, n = 6). The left lateral position had no effect on renal variables, whereas left atrial diameter increased (32 +/- 1 to 35 +/- 1 mm, P < 0.05) and mean arterial pressure decreased (90 +/- 2 to mean value of 85 +/- 2 mmHg, P < 0.05). In conclusion, the prone position reduced stroke volume and increased sympathetic nervous activity, possibly because of mechanical compression of the thorax with slight impediment of arterial filling. The mechanisms of the slightly augmented urine output in prone position require further experimentation.     

Hormonal responses to fasting and refeeding in chronic renal failure patients

To study anorexia in chronic renal failure (CRF) patients, we measured appetite-related hormones in seven CRF patients and four controls. Plasma concentrations and fractional changes from baseline (values from day 1, 0800) are listed as control vs. CRF (means +/- SE). Leptin, although higher in CRF (5.6 +/- 1.7 and 34 +/- 17 ng/ml), was suppressed after fasting; decrements were -51 +/- 9 and -55 +/- 8%. Nocturnal surge present during feeding was abolished upon fasting in both groups. Neuropeptide Y (NPY) was elevated in CRF (72 +/- 12 vs. 304 +/- 28 pg/ml, P = 0.0002). NPY rhythm, reciprocal to that of leptin, was muted in CRF. Basal cortisol was similar in both groups (17 +/- 3 and 17 +/- 2 microg/dl). In the controls, cortisol peaked in the morning and declined in the evening. CRF showed blunted cortisol suppression. Decrements were -61 +/- 3 and -20 +/- 9% at 1800 on day 1 (P = 0.008) and -61 +/- 8 and -26 +/- 8% at 2000 on day 2 (P = 0.02). Basal ACTH (25 +/- 5 and 54 +/- 16 pg/ml) as well as diurnal pattern was not statistically different between the groups. Baseline insulin was 6 +/- 1 and 20 +/- 9 microU/ml. During fasting, insulin was suppressed to -64 +/- 10 and -51 +/- 9%, respectively. Upon refeeding, increments were 277 +/- 96 and 397 +/- 75%. Thus, in our CRF patients, anorexia was not due to excess leptin or deficient NPY. Impaired cortisol suppression should favor eating. Insulin suppression during fasting and secretion after feeding should enhance both eating and anabolism. The constant high NPY suggests increased tonic hypersecretion.     

Plasma somatostatin-like immunoreactivity responses to a mixed meal and the heterogeneity in healthy and non-insulin-dependent (NIDDM) diabetics

Peripheral plasma somatostatin-like immunoreactivity (SLI) was estimated in non-extracted plasma using a specific somatostatin-14 (SS-14) antiserum. The basal plasma SLI level in healthy subjects (n = 18) was 43 +/- 2.9 pg/ml (mean +/- SE) and rose significantly to 8.3 +/- 2.7, 7.3 +/- 1.1 and 5.8 +/- 2.1 pg/ml above the mean basal level 20, 30, and 40 min after a mixed meal, respectively (P less than 0.05). Basal plasma SLI levels in diet (n = 8), sulfonyl urea (n = 8), and insulin groups (n = 8) of non-insulin-dependent maturity onset diabetics (NIDDM) were 50 +/- 1.6, 59 +/- 4.5, and 74 +/- 5.8 pg/ml, respectively. The basal levels for patients with NIDDM were significantly higher than those for healthy subjects (P less than 0.05). No significant increases in plasma SLI were observed after a mixed meal in any group of NIDDM subjects. Elevated plasma SLI levels are considered to be closely related to the severity of the diabetes. The ratios of SS-14 and SS-28 to the total amount of basal plasma SLI were analyzed using high pressure liquid chromatography (HPLC). The ratio of SS-14 to the total SLI was 71-80% in healthy subjects. The ratio of SS-28 to the total SLI increased from 26-30% in the diet group to 50-55% in the group on insulin. These findings suggest a possible pathophysiological role for gastrointestinal somatostatin in NIDDM.     

Plasma somatostatin in normal subjects and in various diseases: increased levels in somatostatin-producing tumors

The plasma levels of somatostatin (SRIF) were studied in normal subjects and patients with various disorders by a sensitive and specific radioimmunoassay. In 45 normal subjects, the fasting plasma SRIF concentrations were 13.3 +/- 5.3 pg/ml (mean +/- SD). Very high concentrations of plasma SRIF, ranging from 125.0 pg/ml to 400.0 pg/ml, were found in all four patients with medullary carcinoma of the thyroid examined and the SRIF levels were changed in parallel with their clinical course after resection of the tumor. A case of pheochromocytoma also showed a relatively high SRIF concentration in plasma (47.0 pg/ml), but the plasma SRIF level decreased to 8.7 pg/ml after removal of the tumor. In normal subjects, plasma SRIF levels did not fluctuate during 2 hr-observation period in basal state. Glucagon (1 mg, iv) and secretin (3 CHRU/kg B.W., iv infusion over 30 min) had no effect on the SRIF levels in the peripheral blood plasma of normal subjects. On intravenous infusion of arginine (0.5 g/kg B.W.) over 30 min, all 6 normal subjects showed a significant increase in plasma SRIF 30-45 min after the start of the infusion (basal value, 11.6 +/- 1.5 pg/ml; peak value, 27.2 +/- 3.0 pg/ml; p less than 0.005). Two cases of medullary thyroid carcinoma showed exaggerated responses after the arginine administration (increases of 103 pg/ml and 157 pg/ml, respectively), suggesting that SRIF was released from the tumor. The findings indicate that plasma SRIF determination in the basal state and after arginine administration is useful for detecting and following up SRIF-producing tumors.     

Chlorpropamide-ethanol induced met-enkephalin secretion in dogs: release mechanisms and biochemical characterisation

Circulating met-enkephalin-like immunoreactivity (MLI) rises in man after chlorpropamide and ethanol although the origin and molecular forms of circulating MLI are not well defined. We have studied the response to oral ethanol in conscious and anaesthetised dogs pretreated with chlorpropamide. In conscious dogs MLI rose from a basal level of 29 +/- 7 pg/ml to a peak of 55 +/- 14 pg/ml 10 min after ethanol (P less than 0.001). In anaesthetised animals, following ethanol, plasma MLI rose in caval (35 +/- 6 pg/ml to a peak of 70 +/- 10 pg/ml), in portal (28 +/- 6 pg/ml to 51 +/- 6 pg/ml) and in adrenal blood (897 +/- 316 pg/ml to 1483 +/- 298 pg/ml; P less than 0.001). Biogel P-4 chromatography of caval and portal basal plasma showed 87% of MLI measured coeluted with the synthetic pentapeptide, while chromatography of peak plasma showed that only 65% coeluted with the pentapeptide and the remaining 35% was of larger molecular size. Sephadex G75 chromatography of adrenal vein plasma revealed three peaks of MLI of differing molecular sizes (8 k = 69.7%; 3-5 k = 12.1% and the pentapeptide = 18.2%). Treatment of the column fractions with trypsin and carboxypeptidase B resulted in the generation of new MLI with peaks of approximate molecular sizes 31 k (10.4%), and 18 k (37.1%) in addition to 8 k (40.0%), 3-5 k (5.0%) and the pentapeptide (7.5%). Acetaldehyde involvement in MLI release was investigated. Following acetaldehyde infusion, plasma MLI rose both in caval (35 +/- 9 pg/ml to 86 +/- 8 pg/ml) and adrenal vein (417 +/- 121 pg/ml to 1768 +/- 433 pg/ml) bloods. Thus we have established an animal model which enables further study of the mechanisms of MLI release and characterisation of the molecular forms. The adrenal medulla, unlike the gut, may be an important source of circulating met-enkephalin and acetaldehyde formation an essential intrinsic component of chlorpropamide-ethanol induced met-enkephalin release.     

Elevated plasma levels of immunoreactive urotensin II and its increased urinary excretion in patients with Type 2 diabetes mellitus: association with progress of diabetic nephropathy

Urotensin II (UII) is the most potent vasoconstrictor peptide ever identified. In order to clarify the pathophysiological role of UII in diabetes mellitus, we examined plasma immunoreactive UII levels and urinary excretion of immunoreactive UII in 10 control subjects and 48 patients with Type 2 diabetes mellitus. The patients were divided into three groups according to the renal function: Group I with Ccr > or = 70 ml/min, group II with 30 < or = Ccr <70 ml/min and group III with Ccr <30 ml/min. Plasma immunoreactive UII levels were elevated in the three diabetic groups compared with normal controls (P <0.05). Group III patients had significantly higher plasma immunoreactive UII levels (15.9 +/- 2.2 fmol/ml, mean +/- S.E.M., n=6) by approximately 1.6-fold than did group I (10.9 +/- 0.9 fmol/ml, n=17) and group II (10.8 +/- 0.8 fmol/ml, n=25) (P <0.05). Urinary excretion of immunoreactive UII was significantly increased in group III patients (52.4 +/- 14.8 pmol/day) by more than 1.8-fold compared with control subjects, groups I and II (P <0.005). Fractional excretion of immunoreactive UII significantly increased as renal function decreased. Presence of diabetic retinopathy or neuropathy had negligible effects on plasma immunoreactive UII levels and urinary immunoreactive UII excretion. Reverse phase HPLC analyses showed three immunoreactive peaks in normal plasma extracts and multiple immunoreactive peaks in normal urine extracts. Thus, Type 2 diabetes mellitus itself is a factor to elevate plasma immunoreactive UII levels, and accompanying renal failure is another independent factor for the increased plasma immunoreactive UII levels in Type 2 diabetic patients. Increased urinary immunoreactive UII excretion in Type 2 diabetic patients with advanced diabetic nephropathy may be due not only to the elevated plasma immunoreactive UII levels but also to increased UII production and/or decreased UII degradation in the diseased kidney.     

Elevated plasma levels of endothelin are associated with the severity of sepsis and presence of shock in contrast to the levels of atrial natriuretic peptide

Immunoreactive endothelin (ETi) and atrial natriuretic peptide (ANPi) blood levels were measured by radioimmunoassay in patients with clinically defined sepsis. The interaction between these two peptides and their relation to circulatory shock and mortality were studied. All septic patients (n = 16) had significantly higher ETi (22.3 +/- 11.1 pg/ml) and ANPi (398.3 +/- 154.3 pg/ml) plasma concentrations compared to control subjects (ETi, 4.1 +/- 1.2; ANPi, 59.1 +/- 14.8 pg/ml; n = 13). ETi levels followed the severity of illness according to the APACHE II scoring system and were higher in patients who did not survive. ETi levels were significantly higher in the presence of shock and bacteraemia. Furthermore, ETi correlated well with plasma lactate (r = 0.83, p < 0.05), but not with renal function. ANPi levels did not show correlation with any of these determinants. Serial blood sampling, six consecutive days after admission, showed that ETi levels gradually decreased in normotensive patients in contrast to patients with septic shock. ANPi levels did not show systematic changes in time, and no relationship was observed between ETi and ANPi levels. These results suggest that plasma ETi levels are indicative for disease severity and might have prognostic significance. The role of ANPi during sepsis remains to be eludicated.     

Effects of atrial natriuretic peptide infusion and its metabolism in patients with chronic renal failure.

Synthetic alpha-human atrial natriuretic peptide (hANP) was infused continuously at a rate of 80 ng/kg/min for 20 min into normal volunteers and patients with chronic renal failure (CRF) receiving hemodialysis. Blood pressure (BP) decreased significantly both in normals and in patients with CRF. The magnitude and the duration of the decrease, however, were greater in patients with CRF. The plasma aldosterone concentration (PAC) decreased significantly in normals and only minimally in patients with CRF. The half time (T1/2) of plasma hANP in patients with CRF (M +/- SE: 4.5 +/- 0.5 min) was longer than that in normals (1.8 +/- 0.2 min). Moreover, the metabolic clearance rate in patients with CRF (64 +/- 7 ml/kg/min) was less than in normals (150 +/- 20 ml/kg/min). Thus, the T1/2 in plasma of hANP in patients with CRF was noticeably longer than in a normal control group. These findings suggest that hANP suppresses PAC regardless of electrocyte imbalances and/or volume change induced by kidney dysfunction and that the kidney may be important in degrading hANP.