scholarly journals Studies on the metabolism of 5α-androst-16-en-3-one in boar testis in vivo

1974 ◽  
Vol 144 (2) ◽  
pp. 347-352 ◽  
Author(s):  
Y. A. Saat ◽  
D. B. Gower ◽  
F. A. Harrison ◽  
R. B. Heap
Keyword(s):  
Venous Blood ◽  
Specific Radioactivity ◽  
Testicular Tissue ◽  
Constant Rate ◽  
Sexually Mature ◽  
Venous Plasma

1. [5α-3H]5α-Androst-16-en-3-one (5α-androstenone) was infused at a constant rate for 180min into the spermatic artery of a sexually mature boar. Samples of spermatic-venous blood were collected at 1min intervals for the first 10min of the infusion and thereafter at 15min intervals for the first hour, then at 64, 125, 155 and 172min. After infusion, the testis was removed and immediately cooled to −196°C. 2. From both the testicular tissue and the spermatic-venous plasma, endogenous and3H-labelled androst-16-enes were isolated, characterized and quantitatively determined and their specific radioactivity was calculated. 3. The specific radioactivities of 5α-androstenore, 5α-androst-16-en-3α-ol and 5α-androst-16-en-3β-ol (an-α and an-β) in testicular tissue were different from those in the spermatic-venous plasma, suggesting that these compounds may be present in more than one compartment of the testis and differentially secreted into the spermatic-venous blood. 4. The ratios of the specific radioactivities of an-α and an-β to their respective sulphate conjugates in the testicular tissue were less than the ratios of the same compounds in the spermatic-venous plasma. 5. The patterns of secretion of these labelled compounds in the spermatic-venous blood during the period of infusion were demonstrated. 6. The urine that accumulated during the infusion was analysed and found to contain3H-labelled an-β, conjugated as both glucuronide and sulphate, the specific radioactivities of which were determined. Little or no androst-16-enes occurred as free steroids. 7. The presence of an-β glucuronide in the urine is discussed.

scholarly journals Studies on the biosynthesis in vivo and excretion of 16-unsaturated C19 steroids in the boar

1972 ◽  
Vol 129 (3) ◽  
pp. 657-663 ◽  
Author(s):  
Y. A. Saat ◽  
D. B. Gower ◽  
F. A. Harrison ◽  
R. B. Heap
Keyword(s):  
Venous Blood ◽  
Testicular Tissue ◽  
Transferase Activity ◽  
Left Testis ◽  
Isotope Concentration ◽  
Continuous Drainage ◽  
Extractable Fraction ◽  
Sexually Mature ◽  
Venous Plasma

1. In one experiment [7α-3H]pregnenolone was infused continuously for 12min into the left spermatic artery of a sexually mature boar and blood was collected during this period by continuous drainage from the spermatic vein. After infusion, the testis was removed and immediately cooled to −196°C. 2. From both the testicular tissue and the spermatic venous plasma, 3H-labelled 16-unsaturated C19 steroids were isolated and characterized and their radiochemical purity was established. 5α-Androst-16-en-3α- and 3β-ol occurred mainly as sulphate conjugates and to a lesser extent as free steroids. Only traces of these alcohols occurred as glucosiduronate conjugates. 5α-Androst-16-en-3-one was found in the free (ether-extractable) fraction. 3. The isotope concentration of each of the 3H-labelled 16-unsaturated C19 steroids in testicular tissue was different from that in spermatic venous plasma. 4. The ratios of tritiated 5α-androst-16-en-3α- and 3β-ol (free steroids) to their respective sulphate conjugates in the testicular tissue were less than the ratios of the same compounds in the spermatic venous plasma. The possibility that the sulphates are partially hydrolysed by testicular sulphatases before secretion is discussed. 5. In a second experiment, a continuous close-arterial infusion of [7α-3H]pregnenolone into the left testis was performed over a 200min period and all the urine that accumulated during the infusion was collected for analysis. 6. No 3H-labelled 16-unsaturated C19 steroids were detected in the urine as free steroids. Only a trace of 5α-androst-16-en-3α-ol was detected conjugated as glucosiduronate, whereas the corresponding 3β-alcohol occurred mainly as glucosiduronate and to a lesser extent as sulphate. 7. The absence of 5α-androst-16-en-3β-ol glucosiduronate in the spermatic venous blood and its presence in considerable amount in the urine may be attributed to hepatic glucuronyl transferase activity.

Comparative rates of formation, in vivo, of 16-androstenes, testosterone and androstenedione in boar testis

1984 ◽  
Vol 103 (2) ◽  
pp. 179-186 ◽  
Author(s):  
E. L. Hurden ◽  
D. B. Gower ◽  
F. A. Harrison
Keyword(s):  
Binding Sites ◽  
Venous Blood ◽  
Peripheral Circulation ◽  
Total Radioactivity ◽  
Venous Blood Flow ◽  
Large White ◽  
The Third ◽  
Very High ◽  
Venous Plasma

ABSTRACT Three mature Large White boars were anaesthetized and received [7(n)-3H]pregnenolone by continuous infusion into right and left spermatic arteries for up to 180 min. Spermatic venous blood flow was measured by separate timed collections of completely diverted outflow from each testis and blood not sampled was returned to the peripheral circulation. The total radioactivity in plasma from each testis increased markedly during the first 60 min of infusion to reach a plateau from 80 to 180 min. Radiolabelling of 5α-androst-16-en-3-one, 5α-androst-16-en-3β-ol and -3α-ol showed similar patterns with ratios of mean radioactivity of 5:3:1 respectively between 80 and 180 min. In comparison, the amounts of tritiated 4,16-androstadien-3-one formed were very small. The radiolabelling of testosterone and 4-androstenedione occurred more rapidly than that of the 16-androstenes and reached maxima by 30 min. However the amounts were only one-fifth (testosterone) and one-tenth (4-androstenedione) those of the combined quantities of tritiated 16-androstenes. Addition of human chorionic gonadotrophin (hCG) to the infusate to one testis in each animal (so that 5000 i.u. hCG were delivered in 15–20 min) produced no change in the outputs of radiolabelled steroids although radioimmunoassay of spermatic venous plasma in samples from the third experiment showed a transient increase in the concentration of 4-androstene-3,17-dione during the hCG infusion. It is suggested the lack of response to hCG could be produced by saturation and down regulation of binding sites by the very high local concentrations of hCG. J. Endocr. (1984) 103, 179–186

scholarly journals In vivo threonine oxidation in growing pigs fed on diets with graded levels of threonine

1996 ◽  
Vol 75 (6) ◽  
pp. 825-837 ◽  
Author(s):  
N. Le Floc'h ◽  
C. Obled ◽  
B. Sève
Keyword(s):  
Specific Radioactivity ◽  
Vena Cava ◽  
Live Weight ◽  
Growing Pigs ◽  
Whole Body ◽  
Constant Infusion ◽  
Balanced Diet ◽  
Liver And Pancreas ◽  
Venous Plasma

Threonine oxidation to glycine was investigated in vivo in twelve growing pigs (27·4 kg live weight) fed on one of the following three diets with graded levels of threonine supply: a low-threonine diet (LT), a control well-balanced diet (C) or a high-threonine diet (HT), during 10h constant infusion of L-[1-13C]threonine and [2-3H]glycine in the cranial vena cava and [l-14C]glycine in the portal vein.13C-threonine and glycine enrichments and [3H]glycine and [14C]glycine specific radioactivities (SR) were determined at plateau in peripheral venous plasma, liver and pancreas. Glycine praduction rates calculated from plasma [2-3H]glycine or [1-14C]glycine SR gave similar values suggesting that [l-14C]glycine SR could be used in order to estimate whole-body glycine flux. The high pancreas [1-13C]glycine enrichment provided evidence that the pancreas may be, with the liver, a major site of threonine oxidation to glycine. Moreover, the present findings suggest that threonine transport into the Liver could be the limiting step of threonine oxidation in this tissue when dietary threonine supply is low. Total threonine oxidation to glycine, calculated from plasma values of enrichment and specific radioactivity, was low and constant when the estimated absorbed threonine was lower than 4 g/d and increased for higher amounts of absorbed threonine.

THE FORMATION OF OESTROGENS BY THE AUTOTRANSPLANTED OVARY OF THE EWE PERFUSED IN VIVO WITH C19 STEROIDS

1970 ◽  
Vol 65 (2) ◽  
pp. 244-260 ◽  
Author(s):  
Andre Rado ◽  
John A. McCracken ◽  
David T. Baird
Keyword(s):  
Steady State ◽  
Luteinizing Hormone ◽  
Venous Blood ◽  
The Other ◽  
Temporary Increase ◽  
Main Route ◽  
Ovarian Artery ◽  
Constant Rate ◽  
Control Samples

ABSTRACT The autotransplanted ovary of the ewe was perfused in vivo via the ovarian artery with either 14C or 3H labelled C19 steroids. 17β-Oestradiol was the major phenolic steroid isolated in ovarian venous blood from either testosterone or androstenedione. Smaller amounts of oestrone were obtained but there was no 17α-oestradiol, oestriol nor conjugated oestrogens isolated. The yield of oestrogen was approximately ten fold greater from androstenedione than from testosterone suggesting that the main route of oestrogen biosynthesis in the ovine ovary is via the former steroid. The effect of infusing luteinizing hormone (LH) at the rate of 10 μg per hour on the conversion of androstenedione to 17β-oestradiol was measured in 5 experiments. In 2 experiments, when the steady state was not achieved, the increasing rate of conversion was halted. On the other hand LH resulted in a temporary increase followed by a decrease in the rate of conversion in the remaining 3 experiments in which there was a constant rate of conversion in the control samples. These results are compatible with the concept that LH stimulates the aromatisation of androstenedione to oestrogens by the ovary in vivo.

ROLE OF DEHYDROEPIANDROSTERONE AND ITS SULPHATE IN SYNTHESIS OF TESTOSTERONE BY HUMAN TESTES IN VIVO AND IN VITRO

1970 ◽  
Vol 46 (1) ◽  
pp. 21-28 ◽  
Author(s):  
M. C. RAHEJA ◽  
O. J. LUCIS
Keyword(s):  
Free Testosterone ◽  
Testicular Tissue ◽  
Dehydroepiandrosterone Sulphate ◽  
Venous Plasma

SUMMARY The synthesis of testosterone from [4-14C]dehydroepiandrosterone (DHEA) and [7α-3H]dehydroepiandrosterone sulphate (DHEA-S) by human testes in vivo and in vitro was investigated. Neither free testosterone nor free DHEA was found in a perfused testis or the spermatic venous plasma after the infusion of [7α-3H]DHEA-S into the spermatic artery in vivo, whereas 3H-labelled free DHEA, testosterone and androstenedione were isolated after incubation of testicular tissue with the same substrate in vitro. Only 14C-labelled testosterone was found in the spermatic venous effluent and in the testis after infusion of a mixture of equimolar amounts of [7α-3H]-DHEA-S and [4-14C]DHEA into the spermatic artery in vivo. Testosterone containing 3H and 14C was isolated after incubation of testicular tissue with a mixture of the two substrates in vitro.

AN ASSESSMENT OF THE POSSIBLE ROLE OF 17α,20α-DIHYDROXY-4-PREGNEN-3-ONE IN THE REGULATION OF TESTOSTERONE SYNTHESIS BY RAT AND RABBIT TESTIS

1974 ◽  
Vol 61 (3) ◽  
pp. 401-410 ◽  
Author(s):  
H. W. A. de BRUIJN ◽  
H. J. van der MOLEN
Keyword(s):  
Venous Blood ◽  
Competitive Inhibitor ◽  
Testicular Tissue ◽  
Seminiferous Tubules ◽  
Interstitial Tissue ◽  
Lyase Activity ◽  
Testosterone Biosynthesis

SUMMARY 17α,20α-Dihydroxy-4-pregnen-3-one is a competitive inhibitor of C17,20-lyase activity in rat testicular tissue in vitro and the significance of this inhibition in vitro was evaluated for testosterone biosynthesis in rat and rabbit testis in vivo. It is concluded that 17α,20α-dihydroxy-4-pregnen-3-one is not involved in the regulation of C17,20-activity in vivo, because it was not possible to detect any 17α,20α-dihydroxy-4-pregnen-3-one in rat and rabbit testicular tissue or in testicular venous blood. If present, the levels are lower than 10 pmol/g testis. Levels of 17α-hydroxyprogester-one are in the order of 50 pmol/g testis. The C17,20-lyase has a higher affinity for 17α-hydroxyprogesterone than for 17α,20α-dihydroxy-4-pregnen-3-one and hence inhibition under in-vivo conditions is not favoured. In rat testes the 20α-hydroxysteroid dehydrogenase activity, which can convert 17α-hydroxyprogesterone to 17α,20α-dihydroxy-4-pregnen-3-one, was found to be mainly (97%) localized in the seminiferous tubules and not at the site of testosterone formation in the interstitial tissue.

PRODUCTION AND SECRETION OF 5α-DIHYDROTESTOSTERONE BY THE CANINE PROSTATE

1972 ◽  
Vol 69 (2) ◽  
pp. 394-402 ◽  
Author(s):  
Gary C. Haltmeyer ◽  
Kristen B. Eik-Nes
Keyword(s):  
Venous Blood ◽  
Steroid Secretion ◽  
Metabolic Chamber ◽  
Arterial Blood ◽  
Constant Rate ◽  
Animal Preparation ◽  
Storage Pools

ABSTRACT An animal preparation has been developed which permits investigation of steroid secretion by the prostate of the dog. In this preparation the prostate is removed from the dog, placed in a metabolic chamber and infused with the animal's arterial blood via the prostatic arteries at a constant rate. This animal preparation secretes 5α-dihydrotestosterone into the prostatic venous blood. While testosterone is the most probable precursor for secreted 5α-dihydrotestosterone, data from experiments indicate that other steroids may serve as precursors for 5α-dihydrotestosterone in this animal preparation in vivo. The presence of »storage pools« and »secretory pools« for steroids in the infused canine prostate has been discussed.

scholarly journals An isotopic method for measurement of muscle protein synthesis and degradation in vivo

1987 ◽  
Vol 245 (1) ◽  
pp. 223-228 ◽  
Author(s):  
E J Barrett ◽  
J H Revkin ◽  
L H Young ◽  
B L Zaret ◽  
R Jacob ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Protein Turnover ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Specific Radioactivity ◽  
Molar Ratio ◽  
Tissue Blood Flow ◽  
Tissue Protein ◽  
Venous Plasma

In eight anaesthetized post-absorptive dogs we measured the concentration and specific radioactivity of phenylalanine and leucine in arterial and femoral-venous plasma, together with hindlimb flow during a continuous infusion of L-[ring-2,6-3H]phenylalanine and [1-14C]leucine. The femoral-venous plasma concentration was greater than arterial for both phenylalanine and leucine (P less than 0.05 for each). Despite net amino acid release there was a significant removal of both labelled phenylalanine and labelled leucine. Consequently, a significant dilution of specific radioactivity was observed between artery and vein for both radio-tracers. The uptake of leucine from the arterial circulation by the hindlimb exceeded by 2.6-fold that of phenylalanine; the measured molar ratio of leucine to phenylalanine in hindlimb muscle protein averaged 2.4 +/- 0.1. Since phenylalanine is neither synthesized nor degraded by muscle tissue, the measured removal of tracer and the dilution of tracer specific radioactivity across the hindlimb can be used to estimate rates of phenylalanine incorporation into, and release from, tissue protein. The estimated rate of protein synthesis by hindlimb averaged 644 +/- 250 nmol of phenylalanine/min. This was exceeded by the rate of tissue protein degradation (987 +/- 285 nmol of phenylalanine/min). The present results demonstrate that the dilution of the specific radioactivity of labelled phenylalanine can be readily measured across dog hindlimb. This measurement, coupled with an estimate of tissue blood flow, can provide a readily measured, non-destructive, method for estimation of protein turnover in specific muscle beds in vivo. Measurements can be made repeatedly over time in a single experiment, allowing the study of factors which regulate protein turnover. The method developed here in dogs can be readily extended to clinical studies.

Subcutaneous adipose tissue: a source of lactate production after glucose ingestion in humans

1990 ◽  
Vol 258 (5) ◽  
pp. E888-E893 ◽  
Author(s):  
E. Hagstrom ◽  
P. Arner ◽  
U. Ungerstedt ◽  
J. Bolinder
Keyword(s):  
Adipose Tissue ◽  
Subcutaneous Adipose Tissue ◽  
Subcutaneous Tissue ◽  
Venous Blood ◽  
Lactate Production ◽  
Glucose Ingestion ◽  
Lactate And Pyruvate ◽  
Subcutaneous Adipose ◽  
Venous Plasma

The in vivo kinetics of lactate and pyruvate in the extracellular space of subcutaneous adipose tissue after glucose ingestion were investigated in healthy volunteers by the use of a microdialysis sampling technique. Comparison was made with the metabolite levels in venous plasma. The absolute subcutaneous tissue concentrations of lactate and pyruvate were estimated in the fasting state by perfusion with varying lactate- and pyruvate-containing solutions. An equilibrium with the surrounding extracellular fluid was found for both lactate and pyruvate in concentrations similar to those in venous plasma. After glucose ingestion there was an increase in the circulating levels of glucose, lactate, and pyruvate, which returned to base-line values within 3 h. There was a more marked increase in lactate in subcutaneous adipose tissue than in venous blood, and the adipose tissue lactate remained elevated for at least 3 h. In contrast, pyruvate levels increased much less in subcutaneous fat than in venous blood. The addition of isoproterenol (which inhibits adipose tissue glucose metabolism) to the tissue perfusate lowered the subcutaneous tissue lactate levels significantly but did not affect the subcutaneous pyruvate levels. These data suggest that human subcutaneous adipose tissue is a source of in vivo lactate production after glucose ingestion. Since lactate is thought to be a major substrate for glycogen synthesis in the liver, the present findings may provide evidence of a new and important role of the adipose tissue metabolism in the regulation of whole body glucose homeostasis in humans.

scholarly journals The design of experiments using isotopes for the determination of the rates of disposal of blood-borne substrates in vivo with special reference to glucose, ketone bodies, free fatty acids and proteins

1973 ◽  
Vol 136 (3) ◽  
pp. 503-518 ◽  
Author(s):  
Dennis F. Heath ◽  
Roger N. Barton
Keyword(s):  
Fatty Acids ◽  
Steady State ◽  
Free Fatty Acids ◽  
Ketone Bodies ◽  
Specific Radioactivity ◽  
Constant Infusion ◽  
Time Curve ◽  
Constant Rate

1. The two well-known methods of estimating rates of irreversible disposal (R) of blood-borne substrates in vivo by isotope experiments involve estimating the specific radioactivity (S) of the substrate in blood either after single intravenous injection of labelled substrate or during its infusion at a constant rate. The value of R is calculated from the S–time curve, usually by assuming: (i) a metabolic steady state with respect to substrate, (ii) the passage of all substrate through the blood, and (iii) the absence of certain types of recycling via blood. 2. In a theoretical investigation we show how experiments can be performed and R calculated from analyses of blood when one or more of the above assumptions is unjustified, by using glucose, ketone bodies, plasma free fatty acids and proteins as examples. In general the methods require single injection procedures, with estimation of the total quantity of label in the substrate in blood and the substrate concentration instead of only S. Such values give estimates of R with standard errors even when only one blood specimen is taken from each of a group of animals, as is convenient when working with small animals or substrates in low concentration, and when the animals are in a non-steady state in which constant infusion procedures are invalid. 3. Similar methods give the fraction of label injected as one compound which passes through another (the isotopic yield). 4. The methods are not always applicable, and cannot be applied to plasma proteins in some pathological conditions. A questionnaire for assessing their applicability is given.

Sign in / Sign up

Export Citation Format

Share Document