Radioimmunoassay For Plasma Testosterone Research Articles

Further evidence for an inhibitory effect of L-tryptophan loading on testicular functions of rat.

Quantitative analysis of spermatogenesis at stage VII of the cycle of the seminiferous epithelium, radioimmunoassay of plasma testosterone and spectrofluorometric assay of brain 5-hydroxytryptamine (5-HT) levels were performed following administration of L-tryptophan (LT) alone and in Carbidopa pretreated Wistar strain rats. Carbidopa, an inhibitor of peripheral L-aromatic amino acid decarboxylase, was used to prevent the peripheral conversion of LT to 5-HT. The rats were sacrificed in groups on the day after (8th day) and 13 days after (21st day) the cessation of 7 days of treatment. The time duration of 13 days is approximately equivalent to one cycle of the seminiferous epithelium in Wistar strain rats. LT enhanced the brain 5-HT level, the increase being much greater in Carbidopa plus LT treated rats. However, reduction of plasma testosterone was similar in both the treated groups. There was no significant change in count of the germ cells on the day after cessation of treatment. However, marked degeneration of step 7 spermatids was observed when the analysis was performed 13 days after cessation of treatment. Human chorionic gonadotropin (HCG) administration along with Carbidopa plus LT treatment partially prevented the step 7 spermatid degeneration. These findings suggest that the inhibition of spermatogenesis and steroidogenesis following LT administration was secondary to decreased pituitary gonadotropin secretion which is in turn under the influence of brain 5-HT neurones. There is a minimum possibility of a direct action of LT, after conversion to 5-HT, on testicular tissue.

Effect of intraventricular injection of 5,6-dihydroxytryptamine on spermatogenesis and plasma testosterone levels in the rat.

Quantitative evaluation of spermatogenesis at stage VII of the cycle of the seminiferous epithelium and radioimmunoassay of plasma testosterone were performed in adult Wistar rats after intraventricular injection of 5,6-dihydroxytryptamine (5,6-DHT). The rats were killed 2, 10 and 21 days after injection. Brain 5-hydroxytryptamine (5-HT) and plasma testosterone levels were found to be significantly lower in all rats treated with 5,6-DHT. A significant reduction in step 7 spermatid count was also observed after 10 and 21 days. Supplementation with human chorionic gonadotrophin for 21 days in rats injected with 5,6-DHT partially prevented the step 7 spermatid degeneration and increased testosterone levels without producing any effect on brain concentrations of 5-HT. These results suggest that changes in testicular steroidogenesis and spermatogenesis are secondary to pituitary gonadotrophin release which, in turn, is under the influence of brain 5-HT neurones.

Effects of androgen administration on sexual invitations by female rhesus monkeys ( Macaca mulatta)

Pairs of adult rhesus monkeys of opposite sexes (12 pairs) were studied during 1-h mating tests (986 tests). Ovariectomized females received 5 μg oestradiol intravaginally throughout to keep them attractive to males and maintain a relatively constant level of male sexual activity. Females were given subcutaneous silastic implants of testosterone to change their sexual receptivity. A threefold change in sexual invitations resulted from the implantation and removal of testosterone in the absence of any major changes in the behaviour of their male partners. These changes in invitational behaviour therefore reflected an action of the hormone upon an internal mechanism within the female subserving sexual motivation which was independent of changes in the behaviour of the male. Radioimmunoassay of plasma testosterone (109 samples) and plasma oestradiol (86 samples), and gas-liquid chromatography of vaginal secretions (306 samples), facilitated the monitoring of variables needed to interpret the results.

Radioimmunoassay of Plasma Testosterone, with Use of Polyethylene Glycol to Separate Antibody-Bound and Free Hormone

We have developed a reliable radioimmunoassay for testosterone in plasma, polyethylene glycol ("Carbowax 6000") being used to separate antibody-bound and free hormone. Testosteron is separated from interfering steroids, notably dihydrotestosterone, by liquid-liquid partition chromatography on infusorial earth (Celite). The assay is sensitive (9 pg for standards), precise, and accurate. The lowest measurable concentration fo testosterone is 350 ng/liter for plasma from men and 70 ng/liter for plasma from women. Intra- and inter-assay coefficients of variation were 6.9% and 9.7%, respectively, for plasma from men, and 9.6% and 11.8%, respectively, for plasma from women. Our method for separating antibody-bound and free hormone is practical and convenient and may be generally applicable to all radioimmunoassays of steroid hormones in plasma.

Estimation of plasma testosterone without extraction and chromatography

A new radioimmunoassay for plasma testosterone in human blood plasma is described. The assay is performed directly upon the plasma without extraction and purification of the testosterone. Antibodies to testosterone-7α-carboxyethyl thioether-bovine serum albumin are used and data concerning the specificity of these antibodies are given.

Radioimmunoassay of plasma testosterone without chromatography: A comparison of four antisera, and the evaluation of a novel approach to liqui scintillation counting

An attempt has been made to improve the specificity and reduce the cost of radioimmunological methods for the determination of plasma testosterone (T). A comparison has been made of the procedures using Dextrancoated charcoal and saturated ammonium sulphate for the separation of steroid bound to antibody. The results show that the use of ammonium sulphate (50% saturated in the assay tube) with the addition of calcium sulphate (40mg/tube) is more efficient and confers extra specificity into the whole precedure in terms of cross reaction with 5α-dihydrotestosterone. The levels of T have been determined in the same samples of peripheral venous plasma from men and women using antisera to T-3-carboxymethyl oxime-BSA, T-6β-carboxymethyl-BSA, T-7α-carboxymethyl thioether-BSA and T-11α-succinyl-BSA. Statistical analyses of these results suggest that the values for T in plasma from men are independent of the antiserum used, whereas the values in plasma from women are invariably higher using anti-T-7α-carboxyethyl-thioether-BSA. In general lower values are obtained with anti-T-3-carboxymethyl oxime-BSA during gonadal stimulation and suppression. An evaluation is given of a new approach to liquid scintillation counting which reduces the cost of each assay by approximately 65%.