Plasma Testosterone Levels In Mice Research Articles

Effect of hyperprolactinemia induced by pituitary grafts or castration on porphyrin content of the mouse Harderian gland.

The histology and porphyrin concentrations of Harderian glands and plasma prolactin levels were examined in B6C3F1 mice castrated or isografted with pituitaries in combination with the administration of bromocriptine (2-bromo-á-ergocryptine), a potent suppressor of prolactin. Four pituitaries were transplanted underneath the bilateral kidney capsules of each mouse. Furthermore, we investigated Harderian porphyrins and plasma testosterone levels in mice that were castrated or treated with neuroleptic butyrophenone (timiperone), a potent accelerator of prolactin, and treated concurrently with bromocriptine. Light microscopically, pituitary grafts increased the concretion of porphyrin pigments within the Harderian gland lumina. Pituitary grafts or castration increased both Harderian porphyrin concentrations and plasma prolactin levels compared with the intact control mice. In pituitary-grafted or castrated mice, bromocriptine distinctly prevented the rise in both porphyrins and prolactin levels. Administration of butyrophenone did not result in any marked change in testosterone levels, although Harderian gland porphyrins were significantly increased. The present results indicate that in mice prolactin stimulates the porphyrin production of the Harderian gland and has an important role in the regulation of Harderian gland porphyrins.

Correlations between the hypothalamic density of 3H-clonidine-binding sites and plasma testosterone levels in mice.

Correlations between the specific binding of radiolabelled adrenoligands in frontal cortex and hypothalamus, and plasma testosterone levels were investigated in inbred mouse strains. Binding values were structure and genotype dependent. There were significant negative intrastrain and interstrain correlations between hypothalamic binding of 3H-clonidine, an imidazoline with alpha 2-adrenoceptor agonist specificity, and resting testosterone levels. Neither binding of the alpha 1-adrenoceptor antagonist 3H-prazosin nor of the beta-adrenoceptor antagonist 3H-dihydroalprenolol (DHA) correlated significantly with hormone concentrations. The inverse correlation between hypothalamic 3H-clonidine-binding and plasma testosterone levels suggests a possible role of alpha 2-adrenoceptors in the negative regulation of testosterone plasma levels.

Assessment of the Critical Level of Androgen for Growth Response of Transplantable Human Prostatic Carcinoma (PC-82) in Nude Mice

The androgen dependent prostatic carcinoma of human origin, PC-82, was used as a model system to investigate the effect of various levels of androgen on the growth of prostatic tumor tissue. Plasma testosterone levels in mice were correlated to tumor growth and intratumor concentrations of testosterone and 5α-dihydrotestosterone. PC-82 tumor burden remained stable at plasma testosterone levels of 0.8 nmol/1., whereas tumor growth occurred at higher levels and tumor regression was observed at lower plasma levels. This critical level of testosterone corresponded with intratumor testosterone and 5α-dihydrotestosterone concentrations of six to 10 and three to four pmol/gm. tissue, respectively, which are significantly above the levels found in castrated non-supplemented animals (3.1 and 1.4 pmol/gm. respectively). This indicates that remaining concentrations of dihydrotestosterone, which amount to two to three times the castrate level, are not stimulatory for tumor growth in the model of the androgen dependent PC-82 tumor.