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At least 19 recordsLinked to original sources
PubMed1979

Secretion rate and metabolic clearance rate of prolactin in the rat during mid- and late lactation.

The prolactin concentration in the plasma of lactating rats rose less rapidly and attained a significantly lower plateau level in response to suckling on day 20--21 of lactation than it did on day 13--14 of lactation. Neither differences in suckling stimulation of the older pups nor a higher metabolic clearance rate (MCR) of prolactin were implicated in the reduced prolactin concentration seen in the late-lactating rats. The MCR was, in fact, slightly reduced in both conscious and late-lactating rats anaesthetized with urethane when compared with those in mid-lactation. The MCR of prolactin was not significantly altered by urethane anaesthesia in rats on either day of lactation. However, the secretion rate of prolactin, computed from the MCR multiplied by the equilibrium concentration of prolactin during suckling, was considerably reduced (665 to 392 ng/min) from mid- to late lactation. We conclude from these data that the reduced plasma concentration of prolactin in response to suckling in late lactation is the result of an impairment within the prolactin secretory mechanism.

Anesthesia, General↗
PubMed1975

A relationship between the molar proportion of propionic acid and the clearance rate of the liquid phase in the rumen of the sheep.

1. Four rumen-cannulated sheep were given a forage mixture (F) of chopped hay-ground, pelleted, dried grass (92:8, w/w) and two concentrate mixtures (C and S) of ground barley-ground hay-flaked maize (46:24:30 and 56:24:20, by wt respectively) in twenty-four hourly meals each day. Each of the diets was offered in successive periods of 16 d to give a feeding sequence F-S-C-S for one pair of sheep and C-S-F-S for the other pair. 2. The average composition (mol/100 mol) of the mixture of short-chain fatty acids, acetic, propionic and butyric, in the rumen was respectively 70-1, 18-5 and 7-5 with diet F, and 55-8, 24-8 and 13-6 with diet C. With diet S, the pattern of fermentation varied both between animals and in the same animal for different periods having either 'high' (28-39 mol/100 mol) or 'low' (16-21 mol/100 mol) proportions of propionic acid. On average when diet S followed diet F there was less propionic acid in the fermentation mixture than when diet S followed diet C (59-3 acetic, 22-2 propionic and 14-1 butyric as compared with 52-7, 29-4 and 13-1 respectively) but this trend was not significant and there was evidence of interactions between the feeding sequences and the individual sheep. 3. The mean concentrations of ammonia, sodium, potassium and chloride were similar for all diets but the pH and concentrations of calcium, magnesium and phosphorus tended to be higher and the buffering capacity lower for diet F than for diets C or S. In animals receiving diet S there was no relationship between the concentrations of minerals, the pH or buffering capacity and the pattern of fermentation except for ammonia, the concentration of which was high when the molar proportion of propionic acid was low. 4. Rumen volume, outflow rate and clearance rate, determined using polyethylene glycol, were higher for diet F than for diets C and S but within each diet, particularly for diet S, values varied considerably between sheep and between periods. 5. There was evidence of an interrelationship between the molar proportion of propionic acid in the fermentation products and the clearance rate, which indicated that the clearance rate may be an important factor influencing the pattern of fermentation in the rumen.

Acetates↗
PubMed1977

Ipratropium bromide: mucociliary clearance rate and airway resistance in normal subjects.

The effect of ipratropium bromide, a new anticholinergic drug, on the rate of clearance of secretions from the lung and on airways resistance was investigated in 12 healthy subjects in a double-blind cross-over trial with placebo and a control run without aerosol. Before taking the drug the subjects inhaled uniform 5 micrometer tracer particles of polystyrene in which 99mTc had been unleachably incorporated. The initial depth of deposition and the rate of clearance of the particles were obtained from serial gamma counts made externally to the chest over six hours. The difference between drug, placebo and control runs in the deposition patterns of the tracer particles and their subsequent rates of clearance were not significant. The drug treatment resulted in statistically significant falls in specific airway resistance at 1, 2, 3 and 6 hours (P less than 0.02). There was no objective or subjective evidence of side effects from the drug.

Aerosol Propellants↗
PubMedDate not supplied

Blood clearance rates of angiotensin II and its metabolites in sheep: presence of immunoreactive fragments in arterial blood.

1. The blood clearance rates of exogenous (des-1-Asp)-angiotensin II and (des-1-Asp-2-Arg)-angiotensin II calculated from the arterial blood level during steady state infusion in conscious sodium-replete sheep were found to be 125 litre/h (s.d. = 27, n = 18) and 188 litre/h (s.d. = 23, n = 18), respectively. These blood clearance rates were in the same order as values for angiotensin II previously reported. 2. Using descending paper chromatography, immunoreactive fragments of angiotensin II in arterial blood extracts were adequately separated from angiotensin II. Quantitative determination of angiotensin II by direct immunoassay on whole blood extract using recovery tracer to correct for losses during extraction were on the average 31% (n = 9) higher than those obtained after the same blood extract had been subjected to chromatographic separation. 3. The blood clearance rates of exogenous 1-Asp-5-Ile-angiotensin II calculated from infusion rate/blood angiotensin II concentration before and after chromatographic separation were significantly different, being 103 litre/h (s.d. = 16, n = 18) and 134 litre/h (s.d. = 25, n = 9), respectively (P less than 0.001;t-test, 16 d.f.). 4. Our data demonstrate the presence of immunoreactive fragments of angiotensin II in arterial blood of sheep during steady-state infusion and indicate that direct immunoassay on arterial blood extracts without adequate separation may result in artificially higher values of angiotensin II in blood and consequently false value for its clearance rate.

Angiotensin II↗
PubMed1975

Metabolic clearance rate, production rate and mammary uptake of progesterone in the goat.

The dynamics of progesterone uptake and metabolism in the mammary gland of the goat have been measured and related to the metabolic clearance rate and production rate of the hormone determined by tracer kinetic techniques. The metabolic clearance rate of progesterone from blood was 3-13 plus or minus 0-35 (S.E.M.) 1/min in ten experiments on six goats; values tended to be slightly higher in pregnant than in non-pregnant goats. The production rate of progesterone at oestrus, and at day 3 of the normal cycle, was less than 0-01 mug/min. During the luteal phase of the oestrous cycle the production rate was 8-5 and 14-6 mug/min in 2 animals, and in the second half of pregnancy, 15-3 plus or minus 0-6 mug/min (5 animals). Progesterone was extracted from the circulation by the mammary gland of conscious goats with an efficiency of 49-4 plus or minus 11-3% in non-pregnant, and 51-7 plus or minus 11-5% in pregnant aniamals. The mean clearance rate of progesterone by the udder was 0-279 1/min, 8-8% of the metabolic clearance rate. Mammary uptake of progesterone in goats with an actively secreting corpus luteum was 0-64 plus or minus 0-29 mug/min, which gave an estimated value of 0-11-1-88 ng/min/g mammary gland. The mammary extraction of progesterone was investigated in a goat 3 days after oestrus when any high affinity receptor sites would presumably be unoccupied. During the infusion of progesterone into a mammary artery, tissue sample were taken from various organs, including the mammary gland, and the concentration of labelled compounds at steady state was determined. A high mammary extraction of progesterone was found to be determined. A high mammary extraction of progesterone was found to be attributable principally to progesterone metabolism. The metabolites of progesterone were removed from the gland in venous blood and were not stored to any appreciable extent in mammary tissue. Experiments in vitro confirmed the findings in vivo that mammary tissue metabolized labelled progesterone and also pregnenolone and androstenedione; metabolism of dehydroepiandrosterone, oestradiol-17 beta, oestrone and cortisol was relatively small. Confirmation of our previous finding that the mammary gland of the goat can synthesize progesterone from labelled pregnenolone infused into the gland in vivo, further implicated this organ as an active site of metabolism of certain steroids. The physiological role of steroid metabolism in the mammary gland is discussed.

Androstenedione↗
PubMed1978

The use of specific radioimmunoassays to determine the renal clearance rates of estrone and 17 beta-estradiol during the menstrual cycle.

Specific RIAs requiring ether extraction only were established for estrone and 17 beta-estradiol both in plasma and in urine from the nonpregnant female. These assays were used to measure the renal clearance rates of estrone and of 17 beta-estradiol in eight ambulatory women in the follicular and in the luteal phases of the menstrual cycle. The mean (+/-SE) for the renal clearance rate of estrone was 0.71 +/- 0.058 ml/min in the follicular phase and 1.26 +/- 0.35 ml/min in the luteal phase. The mean (+/-SE) renal clearance rate of 17 beta-estradiol was 0.44 +/- 0.055 ml/min in the follicular phase and 0.29 +/- 0.043 ml/min in the luteal phase. There was no significant difference in the renal clearance rates of either estrone or of 17 beta-estradiol between the follicular and luteal phases of the cycle. The renal clearances of estrone and 17 beta-estradiol were highly correlated (r = 0.84; P less than 0.01). The renal clearance rate of estrone was significantly greater than that of 17 beta-estradiol in both phases of the cycle (P less than 0.01).

Estradiol↗
PubMed1976

The clearance rate of maternal plasma prehormones of placental estrogen formation.

A method has been established for the determination of the placental clearance of maternal plasma prehormones by placental estrogen formation during human pregnancy. Utilizing this concept, the placental clearance is calculated as the product of the metabolic clearance rate from maternal plasma of the prehormone and its fractional conversion to estrogen by the placenta. This value equals the volume of maternal plasma cleared of that prehormone by the irreversible formation of its estrogenic product hormone per unit of time. The placental clearance rate technique can be performed by intravenous infusion of isotope-labeled prehormone and product, and the metabolic clearance rate as well as the transfer constant can be measured by techniques employing plasma values or by a combination of plasma and urinary methods. Utilizing this type of study, the placental clearance of plasma prehormones has been observed to be increased initially in women destined to develop pregnancy-induced hypertension but declines prior to the onset of hypertension and continues to decline until delivery is effected. Moreover, the administration of diuretics and/or the institution oental clearance of plasma prehormones from the maternal compartment in normal gravidas, in those destined to develop pregnancy-induced hypertension, and in gravidas who are hypertensive from any cause.

Androstenedione↗
PubMed1977

Metabolic clearance rate of adrenocorticotropin in the rat.

The metabolic clearance rate (MCR) of adrenocorticotropin (ACTH) was estimated after the intravenous infusion of graded rates of the hormone (40-2560 muU/min per 100 g body weight) in rats pretreated with chlorpromazine, morphine, and Nembutal, a preparation which proved effective in blocking endogenous ACTH release. The hormone was infused over a period of 45 min, at which time the plasma ACTH concentration had reached a steady state. A specific and sensitive bioassay, based on the corticosterone production of dispersed adrenal cells, was used to measure the plasma ACTH concentration. With increasing infusion rates of ACTH, a threefold decrease in the MCR of ACTH was observed. Previous studies of our group have shown that the MCR of corticosterone increases as a function of the infusion rate of the steroid. It appears, therefore, that the metabolism of these two hormonal links of the hypothalamo-pituitary-adrenocortical axis vary in opposite fashions as a function of the secretion rate of the hormone.

Adrenocorticotropic Hormone↗
PubMed1979

Bromosulphophthalein clearance rates in sheep with pyrrolizidine liver damage.

Sheep fed a ration containing 50% of dried Heliotropium europaeum showed a marked decline in bromosulphophthalein (BSP) fractional clearance rate during the first 3 months feeding. Thereafter, the response of individual animals varied widely on a time basis, although 3 groups could be identified. In the terminal stages, mean clearance rates were below 20% of initial values, with some sheep showing a decline in excess of 90%. Loss of liver functional capacity was generally much greater than indicated by the degree of damage revealed by histopathology. Thus, a suitably modified test could have considerable prognostic value in the field. In this investigation, all sheep with clearance rates below 0.15 died when exposed to a further period of H. europaeum feeding.

Animal Feed↗
PubMed1976

Increased plasma protein binding and lower metabolic clearance rate of aldosterone in plasma of low cortisol concentration.

During ACTH or cortisol infusion in ten recumbent normal men taking dexamethasone, the metabolic clearance rate of aldosterone increased by 50% as plasma cortisol was raised from low (2 mug/dl) to high concentration (50 mug/dl). Since splanchnic blood flow did not change, a greater efficiency of removal of aldosterone must have occurred, by means of displacement of aldosterone from high-affinity sites on plasma protein. At 37 C, equilibrium dialysis of low-cortisol plasma showed one-third of plasma aldosterone bound to albumin, and 24 to 28% bound to higher-affinity sites on other protein. As plasma cortisol increased, a progressively smaller fraction was tightly bound, approaching zero as transcortin was saturated with cortisol. The addition of large amounts of aldosterone to low-cortisol plasma displaced 14C-cortisol from transcortin binding sites. The results support earlier evidence that a significant fraction of plasma aldosterone is bound to transcortin, from which it is readily displaced by cortisol, resulting in an increased metabolic clearance rate of aldosterone by making a larger fraction available for removal from plasma.

Adrenocorticotropic Hormone↗
PubMed1976

Metabolic clearance rate of dehydroisoandrosterone sulfate. VI. Studies of eclampsia.

The metabolic clearance rate of dehydroisoandrosterone sulfate (MCRDS) was measured in 11 women during an eclamptic episode, and the subjects were then followed for at least 5 years. The MCRDS was usually decreased in primigravid women with eclampsia. However, in eclamptic primigravid women who later developed essential hypertension and/or recurrent hypertension in subsequent pregnancies the MCRDS was elevated. Also, in multiparous women with chronic essential hypertension plus superimposed eclampsia, the MCRDS was increased to above normal values.

Adult↗
PubMed1976

Metabolic clearance rate of dehydroisoandrosterone sulfate. V. Studies of essential hypertension complicating pregnancy.

The metabolic clearance rate of dehydroisoandrosterone sulfate (MCRDS) was determined prospectively in gravidas with and without chronic essential hypertension. In normotensive patients, the MCRDS increased in linear fashion throughout pregnancy. In patients with chronic essential hypertension the MCRDS also increased progressively, but at higher values than in normotensive subjects. In normotensive gravidas who ultimately developed pregnancy-induced hypertension, the MCRDS increased progressively at a higher level than in gravidas who remained normotensive until approximately 4 weeks prior to the onset of clinical symptoms, at which time the MCRDS slowly decreased. Similarly, in gravidas with chronic hypertension who developed superimposed pregnancy-induced hypertension, the MCRDS increased progressively at higher levels than all groups studied until approximately 4 weeks prior to onset of hypertension, when a progressive decline in the MCRDS began.

Chronic Disease↗
PubMed1977

In vitro metabolism of progestins. III. The metabolic clearance rate of medroxyprogesterone acetate in monkeys.

3H-medroxyprogesterone acetate (MPA) was synthesized by selective catalytic tritiation of the delta1-olefinic bond of 6alpha-methyl-17alpha-hydroxy-pregna-1,4-diene-3,20-dione acetate. The metabolic clearance rate of MPA (MCRMPA) was determined in 9 female Rhesus monkeys by the single injection technique. The blood MCRMPA was 201 +/- 19 L/day (42.2 +/- 4.0 L/day/kg) which was approximately the same as that reported for progesterone clearance in the monkey. We conclude that a greater biological activity of MPA compared to progesterone cannot be related to its prolonged retention in the blood. Although both MPA and amino-glutethimide alter the rate of steroid metabolism in some species, neither of these agents influences the metabolic clearance rate of 3H-MPA in the monkey.

Aminoglutethimide↗
PubMed1977

[Plasma concentration and metabolic clearance rate of aldosterone at weaning, at puberty, and in adult guinea pigs].

Plasma aldosterone concentrations were measured by radioimmunoassay and metabolic clearance rates (M.C.R.) were determined by a continuous infusion of H3-aldosterone on day 20 and 50 and at 3, 6 and 24 months in the male and the female guinea-pig. Plasma aldosterone concentration rose gradually from day 20 up to 24 months. At every stage the values were always higher in the female than in the male. M.C.R. (1/24 h/100 g) decreased from day 20 to 24 months and appeared to be sex-dependent in the guinea-pig.

Age Factors↗
PubMed1976

The metabolic clearance rate of dehydroisoandrosterone sulfate. IV. Acute effects of induced hypertension, hypotension, and naturesis in normal and hypertensive pregnancies.

In the present study, the metabolic clearance rate of dehydroisoandrosterone sulfate (MCRDS) decreased in normotensive gravidas during short-term studies utilizing angiotensin II-induced elevation of blood pressure. Therapy with hydralazine hydrochloride in chronic hypertensive gravidas resulted in a decrease in blood pressure and an accompanying decrease in the MCRDS. A variable response was observed in the apparent volume of distribution of DS (AVDDS) during therapy with hydralazine hydrochloride. Decreases in MCRDS also occurred in chronic hypertensive gravidas following therapy with 40 mg. of intravenously administered furosemide despite a failure of blood pressure to be altered. The AVDDS increased in four of five patients receiving furosemide, suggesting a possible direct action of furosemide upon vascular smooth muscle.

Adult↗