scholarly journals The metabolic clearance rate of estradiol-17β in rainbow trout, Salmo gairdneri R., estimated by both single injection and constant infusion methods: Increase during oocyte maturation

1987 ◽  
Vol 66 (1) ◽  
pp. 85-94 ◽  
Author(s):  
J.F. Baroiller ◽  
A. Fostier ◽  
Y. Zohar ◽  
O. Marcuzzi
Keyword(s):  
Rainbow Trout ◽  
Oocyte Maturation ◽  
Clearance Rate ◽  
Single Injection ◽  
Constant Infusion ◽  
Salmo Gairdneri ◽  
Metabolic Clearance ◽  
Metabolic Clearance Rate ◽  
Estradiol 17Β

Production rate, metabolic clearance rate and blood concentration of progesterone in conscious and anaesthetized pregnant rats

1984 ◽  
Vol 102 (3) ◽  
pp. 357-363 ◽  
Author(s):  
B. J. Waddell ◽  
N. W. Bruce
Keyword(s):  
Production Rate ◽  
Clearance Rate ◽  
Blood Concentration ◽  
Constant Infusion ◽  
Metabolic Clearance ◽  
Metabolic Clearance Rate ◽  
Short Term ◽  
Pregnant Rats ◽  
Pregnant Rat ◽  
Anaesthetized Rats

ABSTRACT Both production rate and metabolic clearance rate (MCR) of progesterone may vary rapidly and so effect short-term changes in blood concentration of the hormone. Here, a constant infusion and sampling technique was used to estimate these three characteristics of progesterone metabolism in seven conscious and ten anaesthetized rats on day 16 of pregnancy. After steady state was achieved, four samples were collected during a 1-h period from each rat. Mean values for production rate and MCR of progesterone in conscious rats were 14·0 ±1·4 μmol/day and 63·2 ± 6·2 litres/day respectively. Both values were substantially reduced in anaesthetized rats (8.6 ±0·8 μmol/ day and 39·4± 3·4 litres/day respectively) and so blood concentration was unchanged. The production rate was positively related to the total mass of luteal tissue (common correlation coefficient, r = 0·61, P <0·05). There were no consistent changes in the three characteristics with time but variation within rats was high. The estimated coefficients of variation for production rate, MCR and blood concentration within rats were 26, 18 and 17% in conscious and 27, 20 and 23% in anaesthetized rats respectively. Short-term changes in production rate and MCR generally were in the same direction (P <0·05). This reduced variation in blood concentration which would otherwise have occurred if production rate and MCR were unrelated. The pregnant rat is clearly capable of rapid shifts in production rate, MCR and blood concentration of progesterone and the positive relationship between production rate and MCR has a homeostatic effect on blood concentration. J. Endocr. (1984) 102, 357–363

Increased clearance of lactate after short-term training in men

1995 ◽  
Vol 79 (6) ◽  
pp. 1862-1869 ◽  
Author(s):  
S. M. Phillips ◽  
H. J. Green ◽  
M. A. Tarnopolsky ◽  
S. M. Grant
Keyword(s):  
Blood Lactate ◽  
Clearance Rate ◽  
Maximal Oxygen Consumption ◽  
Lactate Concentration ◽  
Blood Lactate Concentration ◽  
Constant Infusion ◽  
Metabolic Clearance ◽  
Metabolic Clearance Rate ◽  
Short Term ◽  
Mitochondrial Potential

A short-term training model previously shown to result in a tighter metabolic control in working muscle in the absence of an increase in mitochondrial potential was used to examine changes in lactate turnover. Lactate flux was studied before and after 10 days of cycle training [2 h/day at 59% maximal oxygen consumption (VO2max)] in untrained men [VO2max = 45.5 +/- 2.4 (SE) ml.kg-1.min-1). A primed constant infusion of L-[1–13C]lactate was used to examine lactate kinetics during a prolonged exercise protocol (90 min at 59% VO2max). Rate of appearance of lactate increased with exercise (P < 0.01), both pretraining (rest = 30.3 +/- 4.9 ml.kg-1.min-1, exercise = 115 +/- 14 ml.kg-1.min-1) and posttraining (rest = 28.4 +/- 4.7 ml.kg-1.min-1, exercise = 112 +/- 13 ml.kg-1.min-1). Despite a lower blood lactate concentration (P < 0.05) during exercise after training, there was no difference in the rate of appearance of lactate. Training increased (P < 0.05) the metabolic clearance rate of lactate during exercise from 36.8 +/- 4.8 to 51.4 +/- 6.8 ml.kg-1.min-1. These findings indicate that at least part of the lower exercising blood lactate observed after training is due to an increase in metabolic clearance rate. In addition, the lower intramuscular lactate levels suggest a decreased recruitment of glycolysis particularly early in exercise.

Effect of human pregnancy on metabolic clearance rate of oxytocin

1990 ◽  
Vol 259 (1) ◽  
pp. R21-R24
Author(s):  
S. Thornton ◽  
J. M. Davison ◽  
P. H. Baylis
Keyword(s):  
Clearance Rate ◽  
Late Pregnancy ◽  
High Plasma ◽  
Constant Infusion ◽  
Aminopeptidase Activity ◽  
Metabolic Clearance ◽  
Metabolic Clearance Rate ◽  
Human Pregnancy ◽  
In Pregnancy

The metabolic clearance rate (MCR) of oxytocin (OT) was determined by use of constant infusion techniques to achieve low and high plasma OT concentrations in 10 women in late pregnancy and again 8-10 wk postpartum (mean plasma oxytocinase activity was 2.1 IU/ml plasma at term and less than 0.1 IU/ml plasma 8-10 wk postpartum). At the lower plasma OT concentrations (5.0 and 5.2 pg/ml, pregnant and postpartum, respectively) produced by infusion of 17.9 ng/min in pregnancy and 4.3 ng/min postpartum, mean MCR of OT was increased fourfold during pregnancy (5.7 +/- 0.6 and 1.3 +/- 0.1 l/min, pregnant and postpartum, respectively; P less than 0.001). At the higher plasma OT concentrations (8.0 and 8.0 pg/ml, pregnant and postpartum, respectively) produced by infusion of 35.7 ng/min in pregnancy and 8.5 ng/min postpartum, mean MCR of OT was likewise markedly increased during pregnancy compared with postpartum values (7.1 +/- 1.9 and 1.4 +/- 0.1 l/min, respectively; P less than 0.01). The MCR of OT was independent of plasma concentration (between 5 and 8 pg/ml) during pregnancy and in the postpartum period. It is concluded that the MCR of OT is increased markedly during human pregnancy. This may be due to concomitant increases in in vivo cystine aminopeptidase activity or other less specific pregnancy-associated metabolic changes.

Metabolism of pure human erythropoietin in the rat

1984 ◽  
Vol 247 (1) ◽  
pp. F168-F176 ◽  
Author(s):  
D. S. Emmanouel ◽  
E. Goldwasser ◽  
A. I. Katz
Keyword(s):  
Clearance Rate ◽  
Gel Filtration ◽  
Kidney Tissue ◽  
Molecular Size ◽  
Constant Infusion ◽  
Metabolic Clearance ◽  
Metabolic Clearance Rate ◽  
Concentration Difference ◽  
Human Erythropoietin

The metabolism of pure human erythropoietin (EPO) labeled with 125I was studied in the rat. Concentrations of the labeled hormone (125I-EPO) in plasma and urine were measured by both trichloroacetic acid precipitation and gel filtration. During steady-state conditions the metabolic clearance rate of 125I-EPO was slow, averaging 256 +/- 7 microliter. min-1 X kg-1 of which only 19 +/- 2 microliter X min-1 X kg-1 (or 7.4 +/- 0.8% of the metabolic clearance rate) could be accounted for by excretion of the labeled hormone in the urine. Urinary clearance of 125I-EPO amounted to less than 0.3% of the glomerular filtration rate, and there was no detectable arteriovenous concentration difference of 125I-EPO across the kidney. After both pulse injection and constant infusion to equilibrium, disappearance of 125I-EPO from the circulation could be approximated by a single exponential function: plasma half-life was 3.5 +/- 0.2 h in normal rats and was prolonged to 4.4 +/- 0.3 h (P less than 0.05) in animals with ligated renal pedicles. Although kidney homogenates degraded 125I-EPO in vitro (optimum pH 4.5), the hormone did not accumulate in the kidney when injected intravenously. We conclude that EPO metabolism is extremely sluggish compared with that of other polypeptide hormones. Whereas kidney tissue is capable of degrading EPO in vitro, the physicochemical characteristics of this glycoprotein (molecular size, shape, and charge) probably impede its access to degrading sites and therefore account for the limited contribution of renal extraction and excretion to the metabolic clearance of the hormone.

Catecholamine physiology in ovine fetus. II. Metabolic clearance rate of epinephrine

1984 ◽  
Vol 246 (4) ◽  
pp. E350-E355
Author(s):  
S. M. Palmer ◽  
G. K. Oakes ◽  
R. W. Lam ◽  
C. J. Hobel ◽  
D. A. Fisher
Keyword(s):  
Clearance Rate ◽  
Blood Gases ◽  
Constant Infusion ◽  
Plasma Norepinephrine ◽  
Base Line ◽  
Metabolic Clearance ◽  
Metabolic Clearance Rate ◽  
Control Value ◽  
Fetal Plasma ◽  
Arterial Blood

This study measured the metabolic clearance rate (MCR) of epinephrine (E) in 13 chronically catheterized fetal lambs between 120 and 145 days gestation. The E-MCR was determined by a constant infusion method at an E infusion rate of 0.1 microgram/kg estimated fetal wt. Fetal and maternal arterial blood samples were taken for measurements of catecholamine levels, pH, blood gases, and glucose. There was a significant positive correlation between gestational age and E-MCR (r = 0.87, P less than 0.001). The E production rate in fetuses less than 132 days (n = 6) (1,234 +/- 301 pg/min) was not significantly different from fetuses greater than or equal to 132 days (n = 7) (1,195 +/- 242). Catecholamine infusion resulted in a decrease in pH from a control value of 7.37 +/- 0.01 to 7.31 +/- 0.01 by 15 min of infusion, but there were no significant changes in fetal heart rate or blood pressure. The mean fetal plasma glucose concentration increased 45% above base line at 15 and 20 min and 65% above base line by 30 min of catecholamine infusion. After 60 min of infusion plasma norepinephrine (NE) increased from 380 +/- 60 to 520 +/- 75 pg/ml and plasma dopamine from 100 +/- 20 to 240 +/- 50 pg/ml (both P less than 0.05). These results indicate that E-MCR increases with maturation in the absence of a change in basal E production.

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