Estimation of Testosterone in Human Peripheral Blood Using S 35 -thiosemicarbazide1

412

159

The present aim of in vivo studies of steroid dynamics in the androgen field is to obtain estimates of the total rate of entry of testosterone and its major precursors such as androstenedione into the general circulation, i.e., the blood production rates (1-7). Also required are the secretion rates of this steroid and its precursors, the relative contributions of these secretions to the blood production rates, and a knowledge of the original anatomical sites of these interconversions and secretions.Previous approaches and solutions to these problems have been questioned because in certain situations, when urinary and blood production rate estimates differ, the total rate of entry of steroid into the general circulation cannot be obtained from urinary studies (6, 7). Also the metabolism of a secreted steroid and the same steroid produced from precursor cannot be regarded as being equivalent (8), which is the basic assumption of one urinary approach (2) and one combined blood and urinary approach (6) used to calculate secretion rates. Presumably, both the production and mode of metabolism of a steroid may vary at different anatomical sites (5,(8)(9)(10).To avoid these difficulties, we have measured production and interconversion rates of testosterone and androstenedione directly in .the peripheral circulation. Because the output of steroids from endocrine glands is into the same circulation,

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Androstenedione production and interconversion rates measured in peripheral blood and studies on the possible site of its conversion to testosterone.

Horton¹,

Tait²

1966

412

159

“…Plasma testosterone and androstenedione were estimated by combining the double-isotope techniques using thiosemicarbazide-8S as described by Riondel et al for testosterone (11) with the modification of Lobotsky, Wyss, Segre, and Lloyd (12) and as described by Horton for androstenedione (13) with the modification of Mizuno et al (14). 10-20 ml of plasma was assayed.…”

Section: Methodsmentioning

confidence: 99%

Metabolism of testosterone and androstenedione in normal and ovariectomized women

Abraham¹,

Lobotsky²,

Lloyd³

1969

A B S T R A C T Metabolic clearance rates of testosterone (MCRT) and androstenedione (MCRA) were determined twice during the same cycle in six normal women, using a constant infusion of testosterone-2H and androstenedione-"C. Nonlabeled steroids served as internal standards. Plasma concentrations of testosterone (iT) and androstenedione (iA) were measured, and the blood production of testosterone (PBT) and of androstenedione (PBA) were calculated. The interconversions of these two steroids were also estimated. Six ovariectomized women were studied in the same manner. For testosterone, the mean i in the normal women was not significantly different from that in the ovariectomized subjects, whereas the MCRT and PET were significantly lower in the ovariectomized subjects. For androstenedione, the mean MCRA values of the two groups of subjects were not different, whereas the iA and PBA in the normal women were about double those in the ovariectomized subjects. In comparing the follicular and luteal phases of the menstrual cycle in four of six subjects there was no difference in iT, MCRT, or PBT, whereas iA, MCRA, and PBA were increased in the luteal phase. In one ovariectomized woman infused with testosterone and androstenedione at physiologic levels, MCRT doubled but MCRA remained the same. After six wk on estrogen, the same subject did not show any change in MCRT after infusion of testosterone. It is suggested that MCRT depends on PBT and on plasma binding of testosterone which is partly estrogen dependent.

“…All other solvents were of technical grade and were redistilled prior to use. Pyridine was prepared as described (14). Acetic anhydride was distilled, and the fraction boiling at 1380C was collected.…”

Section: Methodsmentioning

confidence: 99%

Metabolic clearance rates and interconversions of estrone and 17β-estradiol in normal males and females

Longcope¹,

Layne²,

Tait³

1968

173

A B S T R A C T The continuous infusion of 3H-6,7-estrone and 3H-6,7-estradiol has been used to study the metabolic clearance rate (MCR), the interconversions, and the red cell uptake of these steroids in normal males and females. The whole blood MCR of estrone is 1,990 + 120 liters per day/ m2 (SE) in males and 1,910 + 100 liters per day/M2 in females. The whole blood MCR of estradiol is 1,600 + 80 liters per day/M2 in males and 1,360 + 40 liters per day/M2 in females. The values in females do not vary significantly when studied in the follicular or luteal phase of the cycle. At least 35%o of the total estrone metabolism in both sexes is extrasplanchnic and at least 25%o of the total estradiol metabolism in males, and 15%o in-females is extrasplanchnic. The [p] BB21 [transfer constant of estradiol. to estrone, which is equivalent to the fraction of the precursor (estradiol) converted to the product (estrone) when both the infusion of the precursor and the measurement of the product aire in peripheral blood] is 15%o; and the [p]BB"2 [transfer constant of estrone to estradiol, which is equivalent to the fraction of the precursor (estrone) converted to product (estradiol) when both the infusion of the precusor and the measurement of the product are in peripheral blood] is 5%o in both INTRODUCTIONThe metabolic clearance rate (MCR) of a substance, defined as that volume of blood from which it is totally and irreversibly cleared in unit time, is a concept which has been applied to studies of the metabolism of aldosterone, cortisol, progesterone, and the androgens (1-5). In this manner, information has been obtained concerning splanchnic and extrasplanchnic metabolism. In addition, the use of the continuous infusion technique has provided data on the interconversion of androstenedione and testosterone (3,4,6) and on the uptake of steroid hormones into red cells (2).Previous studies of the metabolism of estrone and 17,8-estradiol in nonpregnant humans have provided some data concerning the half-lives of these steroids in plasma (7) and the red cell binding of estrone (8). The major studies have been concerned with urinary metabolites and with the radioactivity appearing in these metabolites after administration of the labeled hormone (9-11). In-The Journal of Clinical Investigation Volume 47 1968 93 formation obtained in this manner however does not always reflect the dynamics of the circulating hormone (4, 12, 13). Therefore, we felt that a study of the metabolic clearance rates and the interconversion of estrone and 17fl-estradiol in blood would provide a fuller picture of the metabolism of these steriods. The plasma MCR of testosterone is much lower than the hepatic plasma flow. This difference indicates incomplete splanchnic extraction for this steroid (3,4,6). However, the plasma MCR of androstenedione is greater than hepatic plasma flow (3, 4, 6). Bardin and Lipsett (13) have reported that the plasma MCR of testosterone is greater for males than for females, and the difference is significant after correction...