Secretory dynamics of 1α-hydroxycorticosterone in the elasmobranch fish, Scyliorhinus canicula

1984 ◽  
Vol 103 (2) ◽  
pp. 205-211 ◽  
Author(s):  
N. Hazon ◽  
I. W. Henderson
Keyword(s):  
Sodium Chloride ◽  
Sea Water ◽  
Specific Activity ◽  
Plasma Concentrations ◽  
High Specific Activity ◽  
Constant Infusion ◽  
Metabolic Clearance ◽  
Plasma Osmolarity ◽  
Scyliorhinus Canicula ◽  
Infusion Technique

ABSTRACT Peripheral plasma concentrations, metabolic clearance rates (MCR) and blood production rates (BPR) of 1α-hydroxycorticosterone (1-OH-B) were determined in female dogfish (Scyliorhinus canicula) under varying environmental conditions. The constant-infusion technique, using high specific activity tritiated 1-OH-B, was applied to measure the MCR, and BPR were derived from the product of plasma concentration and MCR at equilibrium. Urea plasma clearances and apparent BPR were assessed in a similar manner. Fish were adapted stepwise to 140, 120, 90, 80, 70, 60 and 50% normal sea water (about 1000 mosmol/l). In all cases 1-OH-B was the major corticosteroid, cortisol and corticosterone were sought but never detected. In environments of reduced osmolarity, plasma osmolarity, sodium, chloride and urea concentrations all declined, alongside increases in plasma concentrations, MCR and BPR of 1-OH-B. In fish held in environments at concentrations greater than normal sea water, plasma osmolarity, sodium, chloride and urea concentrations all increased. Plasma clearance of urea increased in fish held in environments more dilute than sea water, while it decreased in the more hyperosmotic waters. It is tentatively concluded that homeostasis of plasma composition, with particular respect to urea, is in part regulated by 1-OH-B in the dogfish. J. Endocr. (1984) 103, 205–211

A Comparative Study on the Metabolism of Human Insulin and Porcine Proinsulin in Man

1973 ◽  
Vol 45 (5) ◽  
pp. 633-654 ◽  
Author(s):  
P. H. Sönksen ◽  
Christine V. Tompkins ◽  
M. C. Srivastava ◽  
J. D. N. Nabarro
Keyword(s):  
Human Insulin ◽  
Normal Subjects ◽  
Constant Infusion ◽  
Metabolic Clearance ◽  
Priming Dose ◽  
Metabolic Clearance Rate ◽  
Serum Growth Hormone ◽  
Biological Potency ◽  
Infusion Technique ◽  
Apparent Distribution

1. The metabolism of unlabelled monocomponent human insulin and porcine proinsulin was studied in ten normal subjects (five males and five females) by using a priming dose-constant-infusion technique. In each subject, the metabolic clearance rate (MCR) was measured at four separate steady-state hormone concentrations averaging 16–216 μunits/ml (insulin) and 4·2–42·8 ng/ml (proinsulin). 2. For insulin the MCR fell progressively from 34 ml kg−1 min−1 at a mean fasting insulin concentration of 3·8 μunits/ml to 11·4 ml kg−1 min−1 at the highest concentration achieved (280 μunits/ml); for proinsulin MCR averaged 3·7 ml kg−1 min−1 at a mean plasma concentration of 4·2 ng/ml and fell to 2·71 ml kg−1 min−1 at 10·7 ng/ml, remaining constant thereafter at concentrations up to 71 ng/ml. 3. The half-disappearance time (T½) from the plasma, after the end of the infusion, averaged 4·3 min for insulin and 25·6 min for proinsulin. 4. The apparent distribution space (DS) was similar for both hormones (83 ml/kg of insulin and 98·9 ml/kg of proinsulin). 5. There was a direct correlation between T½ and DS for both hormones. 6. Although the higher MCR of insulin was reflected in its shorter T½ there was, for each hormone, no relationship between MCR and T½. 7. The biological potency of porcine proinsulin, as judged by its effect on plasma glucose, was approximately 5% of that of insulin. 8. The responses of serum growth hormone and Cortisol were shown to be directly related to the degree of hypoglycaemia induced.

Observations on the Intake of Water and Electrolytes by the Duck (Anas Platyrhynchos) Maintained on Fresh Water and on Hypertonic Saline

1968 ◽  
Vol 49 (2) ◽  
pp. 325-339 ◽  
Author(s):  
G. L. FLETCHER ◽  
W. N. HOLMES
Keyword(s):  
Drinking Water ◽  
Sodium Chloride ◽  
Fresh Water ◽  
Hypertonic Saline ◽  
Sea Water ◽  
Plasma Concentrations ◽  
Daily Intake ◽  
Gradual Loss ◽  
Body Weights ◽  
Food And Water Intake

1. Intake of food, water and electrolyte by ducks maintained on fresh water and on hypertonic saline were measured over periods up to several months. 2. Transfer to saline approximately equivalent to 60% sea water was followed during the first 24 hr. by a sharp rise and fall in the plasma concentrations of sodium and chloride, which thereafter remained similar to the concentrations found in the freshwater-maintained birds. 3. Transfer to saline equivalent to 100% sea water resulted in a rise in these concentrations during the first 10 hr., which continued for a period up to 14 days, after which the birds either died or became unhealthy. 4. Upon transfer to saline drinking water (284 mM/l. Na+, 6.0 mM/l. K+) there was a gradual loss of body weight accompanied by a reduction in the food and water intake. Body weights tended to become stable after about 3 weeks, but some individuals continued to lose weight while others regained what they had lost. 5. When the concentration of sodium chloride in the drinking water exceeded 143 mM/l. the amount of sodium chloride ingested remained constant. Thus there was progressive decline in the volume of water drunk as the concentration increased. It would appear therefore that the saline-adapted duck possessed some mechanism whereby the daily intake of sodium chloride was regulated. 6. The cloacal output from saline-adapted ducks over a 24 hr. period showed that only 10% of the ingested sodium was excreted via this pathway as compared with over 70% of the ingested potassium. Most of the sodium appeared to be excreted via the nasal glands. 7. The possible interactions between the renal and extra-renal excretory pathways in the maintenance of homeostasis during adaptation to diets including hypertonic saline or seawater are discussed.

Arginine vasopressin metabolism in dogs. I. Evidence for a receptor-mediated mechanism.

1978 ◽  
Vol 235 (6) ◽  
pp. E591 ◽  
Author(s):  
R E Weitzman ◽  
D A Fisher
Keyword(s):  
Arginine Vasopressin ◽  
Urine Osmolality ◽  
Volume Of Distribution ◽  
Membrane Receptors ◽  
Constant Infusion ◽  
Metabolic Clearance ◽  
Strong Negative Correlation ◽  
Pulse Injection ◽  
Plasma Membrane Receptors ◽  
Infusion Technique

The plasma clearance rates (PCR) of arginine vasopressin (AVP), and iodinated AVP (125I-AVP) were determined after pulse injection in conscious water-loaded dogs. Both the PCR and the apparent initial volume of distribution were significantly greater for AVP than for the biologically inactive iodinated AVP 37.4 +/- 4.8 ml/kg per min vs. 6.7 +/- 0.8 ml/kg per min (P less than 0.001) and 12.7 +/- 0.9% body wt vs. 7.1 +/- 0.4% body wt (P less than 0.001). AVP clearance was then determined by the constant-infusion technique at doses that produced equilibrium AVP concentrations within and above the physiological range. AVP-PCR was 37.4 +/- 7.1 ml/kg per min at 34 microU/kg per min, which was comparable to that after pulse injection (P less than 0.9). AVP clearance fell progressively, and urine osmolality progressively increased with increasing AVP infusion rates to plateau values at 136 microU/kg per min; a strong negative correlation was observed between mean AVP-PCR and urine osmolality (r = -0.993). The data suggest a relationship between the biological activity of AVP and its clearance. It is proposed that plasma membrane receptors may mediate a portion of the metabolic clearance of AVP.

Drawbacks of the constant-infusion technique for measurement of renal function

1995 ◽  
Vol 268 (4) ◽  
pp. F543-F552 ◽  
Author(s):  
B. A. Van Acker ◽  
G. C. Koomen ◽  
L. Arisz
Keyword(s):  
Renal Function ◽  
Steady State ◽  
Plasma Concentrations ◽  
Constant Infusion ◽  
Urinary Recovery ◽  
Infusion Method ◽  
Pah Clearance ◽  
The Difference ◽  
Infusion Technique ◽  
Extrarenal Clearance

We investigated the validity of the steady-state constant infusion method (CIM), in which quantitative urinary recovery and constant plasma concentrations of the solute infused are required. Successive 3-h clearances of inulin and p-aminohippuric acid (PAH) were determined for 27 h in 25 patients with renal disease. Results were compared with the standard method of bladder clearance (StM) and with a modified CIM (ModCIM). The 24-h urinary recovery was incomplete for both inulin and PAH. Mean 24-h ModCIM inulin clearance overestimated StM by 4.5 ml.min-1 x 1.73 m-2 (range 0–9, P < 0.001) independent of the extent of renal impairment and pointed to slow distribution and/or extrarenal clearance of inulin. For PAH, the difference between ModCIM and StM clearance was related to the average PAH clearance by ModCIM and StM (r = 0.78). Furthermore, neither plasma inulin nor PAH became completely constant, because of the circadian rhythm in renal function. In conclusion, the conditions of the steady-state CIM technique are not fulfilled, and the method is not suitable for accurate measurement of inulin and PAH clearance, especially when the clearance is low.

Estimation of tissue protein synthesis in rats fed diets labeled with (U-14C)tyrosine

1976 ◽  
Vol 231 (4) ◽  
pp. 1018-1023 ◽  
Author(s):  
ME Harney ◽  
RW Swick ◽  
NJ Benevenga
Keyword(s):  
Protein Synthesis ◽  
Specific Activity ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Constant Infusion ◽  
Liver Protein ◽  
Fractional Rate ◽  
Tissue Protein Synthesis ◽  
Physiological Approach ◽  
Infusion Technique

The rate of liver and muscle protein synthesis has been measured in 27 rats after feeding L-[U-14C]tyrosine in L-amino acid diets prepared as agar gels. Constant specific activity of the free tyrosine pool, as indicated by constant excretion of 14CO2, was reached within 2 h of feeding and was maintained for the remaining 6 h of the 8-h experiment. Muscle protein synthesis was decreased (P less than 0.05) in rats fed a 0.3% methionine diet compared with rats fed this diet supplemented with 0.51% cystine (fractional rate of synthesis, ks: 0.098 vs. 0.121). No effect (P greater than 0.05) of these diets on liver protein synthesis was observed (ks: 0.603 vs. 0.532). Protein synthetic rate was also determined by the constant-intravenous infusion technique in 17 rats fed unlabeled diets. The two techniques gave similar estimates. Restraint of the rats or the infusion of saline had no measurable effect on the rate of protein synthesis in rats fed labeled diets. This feeding technique is essentially equivalent to the constant-infusion technique and offers an easier, more physiological approach to achieving a steady state.

Influence of nephrectomy on the glucoregulatory response to insulin administration in the rat

1980 ◽  
Vol 58 (3) ◽  
pp. 301-305 ◽  
Author(s):  
Gavino Perez ◽  
Giacomo Carteni ◽  
Biagio Ungaro ◽  
Luigi Saccà
Keyword(s):  
Plasma Concentrations ◽  
Insulin Injection ◽  
Constant Infusion ◽  
Glucose Turnover ◽  
Metabolic Clearance ◽  
The Face ◽  
Plasma Insulin Levels ◽  
Glucagon And Insulin ◽  
Glucose Output

Insulin sensitivity and resistance were examined in vivo in uremic rats by using tracer methods which permit the assessment of "non-steady-state" glucose kinetics. By relating the changes in the rates of glucose output by the liver (Ra), uptake by tissues (Rd), and metabolic clearance (MCR) to immunoreactive glucagon and insulin, it was possible to assess the tissue sensitivity to physiologic and supraphysiologic levels of these two hormones and the site of insulin resistance. The effect of an intravenous injection of insulin (100 mU) on glucose turnover was studied in acutely uremic rats 15 h after bilateral nephrectomy and in sham-operated controls, in the postabsorptive state. Glucose output by the liver and uptake by tissues were determined by the primed constant infusion technique using [3-3H]glucose. Under basal conditions, no significant differences in Ra and Rd between the two groups were observed, while a significant hyperglycemia and a reduced glucose metabolic clearance rate in the face of hyperglucagonemia and normal plasma insulin levels were observed in nephrectomized rats. After insulin injection, the glycemic curves were similar in the two groups, while Ra, Rd, and MCR displayed significantly lower values in nephrectomized rats in the face of higher plasma concentrations of insulin and glucagon. It was concluded that acute uremia in the rat is characterized by a loss of the normal ability of insulin to promote peripheral glucose uptake with retention of hepatic sensitivity to insulin.

Sodium, Chloride and Water Balance of the Intertidal Teleost, Xiphister Atropurpureus

1967 ◽  
Vol 47 (3) ◽  
pp. 513-517
Author(s):  
DAVID H. EVANS
Keyword(s):  
Sodium Chloride ◽  
Water Balance ◽  
Sea Water ◽  
Plasma Concentrations ◽  
Xiphister Atropurpureus

1. Studies were undertaken to determine the degree of regulation of sodium, chloride and water displayed by the intertidal teleost, Xiphister atropurpureus, over a range of salinities. 2. The plasma concentrations of sodium and chloride declined by approximately 15 % in 10 % sea water (48 mM-Na/kg.) and the intracellular and extracellular spaces increased by approximately 6 % in 10% sea water.

Δ5-androstenediol: kinetics of metabolism and binding to plasma proteins in normal post-menopausal women

1982 ◽  
Vol 99 (2) ◽  
pp. 309-313 ◽  
Author(s):  
Charles E. Bird ◽  
John Tremblay ◽  
Valerie Masters ◽  
Albert F. Clark
Keyword(s):  
Young Women ◽  
Plasma Proteins ◽  
Constant Infusion ◽  
Metabolic Clearance ◽  
Androgenic Activity ◽  
Menopausal Women ◽  
Post Menopausal ◽  
Infusion Technique ◽  
Kinetics Of ◽  
Free Plasma

Abstract. Δ5-androstenediol (Δ5-diol) while having minimal androgenic activity is of potential biological importance because it binds to oestrogen receptors and has oestrogenic activity in several systems. We have examined Δ5-diol metabolism in post-menopausal women utilizing the constant infusion technique. The metabolic clearance rate for 11 subjects was 763 ± 50 1/24 h or 467 ± 30 1/m2/24 h. Labelled dehydroepiandrosterone, testosterone, Δ4-androstenedione, androsterone and the sulphates of Δ5-diol, dehydroepiandrosterone and androsterone were found in the plasma. Of all the kinetic parameters only the conversion ratio for dehydroepiandrosterone sulphate was different from that for young women (4.958 ± 0.410 for young women vs 3.084 ± 0.220 for older women). The plasma concentration of Δ5-diol was 0.94 ± 0.19 ng/ml and the calculated blood production rate was 686 ± 80 μg/24 h. The per cent free plasma Δ5-diol was 4.6 ± 0.25. These values are slightly lower but not significantly different from those previously reported for normal young women.

Lactate metabolism in resting and exercising dogs

1976 ◽  
Vol 40 (3) ◽  
pp. 312-319 ◽  
Author(s):  
B. Issekutz ◽  
W. A. Shaw ◽  
A. C. Issekutz
Keyword(s):  
Constant Infusion ◽  
Metabolic Clearance ◽  
Turnover Rates ◽  
Lactate Turnover ◽  
Hepatic Glucose ◽  
Lactate Levels ◽  
Glucose Output ◽  
Infusion Technique ◽  
Linear Manner

The effect of treadmill run on the turnover rates of glucose ([2-3H]glucose) and lactate ([U-14C]lactate), on the rates of oxidation (ROX) of lactate, and its conversion to glucose (L LEADS TO G) were measured with the primed constant-infusion technique. Comparable lactate turnover rates were obtained at rest by infusing epinephrine, or Na-L(+)-lactate with or without norepinephrine. With increasing lactate levels (L) the rate of disappearance (RdL), ROX, and L leads to G increase in a linear manner. At the same lactate level, RdL, ROX, and L leads to G are significantly higher in the running dog. Exercise increased the metabolic clearance rate of lactate threefold. At rest ROX and L leads to G represented about 50% and 18–19% of RdL, respectively. The corresponding values in the running dogs were 55% and 25%, respectively. At rest about 9% of the hepatic glucose output arose from lactate while during exercise this varied from 7 to 26% depending on RdL. It is concluded that a) the working muscle produces and utilizes lactate at the same time, and b) “in vivo” the major factor which controls both ROX and gluconeogenesis is the substrate supply.

scholarly journals Benzodiazepine Receptor Quantification in vivo in Humans Using [11C]Flumazenil and PET: Application of the Steady-State Principle

1995 ◽  
Vol 15 (1) ◽  
pp. 152-165 ◽  
Author(s):  
N. A. Lassen ◽  
P. A. Bartenstein ◽  
A. A. Lammertsma ◽  
M. C. Prevett ◽  
D. R. Turton ◽  
...  
Keyword(s):  
Steady State ◽  
Specific Activity ◽  
High Specific Activity ◽  
Receptor Occupancy ◽  
Occipital Cortex ◽  
Constant Infusion ◽  
Tracer Injection ◽  
Free Concentration ◽  
The Brain

Carbon-11-labeled flumazenil combined with positron emission tomography (PET) was used to measure the concentration ( Bmax) of the benzodiazepine (Bz) receptor in the brain and its equilibrium dissociation constant ( KD) for flumazenil in five normal subjects. The steady-state approach was used injecting the tracer as a bolus of high specific activity. In each subject two studies were carried out. The first study was performed at essentially zero receptor occupancy, the tracer alone study. The second study was performed at a steady-state receptor occupancy of about 50%, achieved by a prolonged constant infusion of nonlabeled (“cold”) flumazenil starting 2 h before the bolus tracer injection and continuing until the end of the scanning period. In this second study the free concentration of unmetabolized flumazenil in plasma water was measured in multiple blood samples. The observed tissue and plasma tracer curves, calibrated in the same units of radioactivity per millimeter, were analyzed in two ways: (a) by the noncompartmental (stochastic) approach making no assumptions regarding number of compartments in the tissue, and (b) by the single-compartment approach assuming rapid exchange (mixing) of tracer between all tissue compartments. The noncompartmental and the compartmental analyses gave essentially the same values for the distribution volume of the tracer, the parameter used for quantitation of the Bz receptor. As the compartmental approach could be applied to a shorter observation period (60 min instead of 120 min) it was preferred. The five subjects had a mean KD value of 12 n M/L of water and Bmax values of the grey matter ranging from 39 ± 11 in thalamus to 120 ± 14 n M/L of brain in occipital cortex. Most previous studies have been based on the pseudoequilibrium approach using the brain stem as a receptor-free reference region. This yields practically the same KD but lower Bmax values than the steady-state approach presented here.

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