Immunoreactive cytochrome P-450(17 alpha) in rat and guinea-pig gonads, adrenal glands and brain.

The cytochrome P-450(17 alpha)-hydroxylase, 17----20 lyase (P-450(17 alpha)) is the key enzyme responsible for the biosynthesis of androgens in steroidogenic organs. Its cellular localization has been examined with an immunohistochemical technique. In immature rat ovary, P-450(17 alpha) was first detected in sparse interstitial cells on postnatal Day 8. The number of immunoreactive interstitial cells increased thereafter and the intensity of P-450(17 alpha) staining in these cells was highest at 3 weeks of age. The intensity of staining then started to decline and was very faint at Day 35. From 6 weeks on, the distribution of immunoreactive P-450(17 alpha) was of the adult type: it was detected exclusively in the thecal cells of the large antral, preovulatory, follicles. P-450(17 alpha) was not detectable during pregnancy except on the day of parturition, when thecal cells were transiently immunoreactive. The staining had vanished 24 h after delivery. Human chorionic gonadotrophin (hCG), injected into immature females on Days 24 to 26, induced P-450(17 alpha) prematurely in thecal cells. When injected on Days 12 to 14 of pregnancy, hCG also induced P-450(17 alpha) in the thecal cells surrounding the largest follicles, whereas the interstitial and luteal cells were not immunostained. The antiprogestin RU486, injected on Day 16 of pregnancy, reinstated P-450(17 alpha) (and P-450scc) immunoreactivity in the thecal cells. Oestradiol selectively suppressed P-450(17 alpha) expression in the thecal cells of RU486-treated females. In immature guinea-pig ovary, P-450(17 alpha) was immunostained in thecal cells, not in interstitial cells, although the interstitial cells expressed the delta 5-3 beta-hydroxysteroid dehydrogenase. P-450(17 alpha) was also immunolocalized in the Leydig cells of rat and guinea-pig testes, and in the guinea-pig adrenal cortex (zonae fasciculata and reticularis), but not in the rat adrenal cortex. P-450(17 alpha) was not detectable in the brain of either rat or guinea-pig.     

Steroid hormone radioautography in cultured cells: Studies with Shionogi carcinoma 115

A radioautographical technique for the localization of soluble compounds in cultured cells is described. It has been used to investigate the distribution of steroid hormones in target cells, and an example is given with the Shionogi carcinoma SC-115, an androgen-sensitive mammary tumor in mice. Experiments at 37 °C have given direct evidence for the specific binding of [³H]-androstanolone (5α-dihydrotestosterone) in the cytoplasm. This result is based on the labeling after incubation with 0.5 nM radioactive androgen, on the isotope dilution-test showing a limited capacity, and on competition assays with other hormones. Results also show the transfer to and the specific binding of the hormone in the nucleus. No cellular labeling has been observed at 0 °C, even when using 10 nM of high specific activity [³H]androstanolone. The technique appears promising for the study of various aspects of the interactions between hormones and isolated cells.     

Cell-specific variations and hormonal regulation of immunoreactive cytochrome P-450scc in the rat ovary

Specific rabbit antibodies to the bovine cholesterol side-chain cleavage cytochrome P-450 (P-450scc) were used to cross-react with the enzyme in the rat ovary. The luteal cells of cyclic, pregnant, and pseudopregnant rats were immunostained. P-450scc was also expressed in the interstitial cells of prepubertal and cyclic adult rats, and in the thecal cells lining the preovulatory follicles. In cyclic females, RU 486 and oestradiol increased the intensity of P-450scc immunostaining. The granulosa cells of ovarian follicles whatever their stage of development, including preovulatory follicles, were not labelled, except after ovulation. The intensity of immunostaining of thecal and interstitial cells decreased during early pregnancy or pseudopregnancy, and disappeared after Day 9, whereas these cells were intensely labelled 24 h after parturition. The immunostaining of thecal and interstitial cells was again detected in 18-day pregnant rats, treated with the antiprogesterone RU 486. It is therefore concluded that both oestradiol and progesterone are involved in P-450scc regulation.     

Studies of the 3beta-hydroxysteroid oxidoreductase activity in rat ventral prostate

The reduction of ³H-androstanolone into 3β-androstanediol was used to study the 3β-hydroxysteroid oxidoreductase activity of rat ventral prostate. This activity is present only in the cytosol and has a pH optimum of 8.5 with NADH as cofactor. The 3β-hydroxysteroid oxidoreductase activity , as compared to 3α-hydroxysteroid oxidoreductase activity, is much lower in the present study than was observed previously during prostate perfusion $\text{in vivo}$ or prostate organ culture superfusion.     

Imagerie moléculaire du transporteur vésiculaire de l’acétylcholine (VACh) par le [123I]-5-iodobenzovézamicol dans la démence de type Alzheimer (DTA)

Alzheimer's disease (AD) is characterized by a premature decline of cholinergic neurons. The 5-IBVM is an analogue of the vesamicol that binds to the presynaptic vesicular acetylcholine transporter (VAChT). The exploration of this target should be useful to make an early diagnosis of AD. Our first aim was to propose a method of non invasive VAChT quantification according to 5-IBVM kinetic. 5-IBVM was injected to four AD patients (age = 77 ± 3.9 years and MMSE = 24.5 ± 1.02) were included in this methodological study. The single-photon emission computed tomography (SPECT) images were obtained at five, 20, 35 and 50 minutes, at then at three, five and 22 hours after intravenous injection of 5-IBVM (185MBq). The time activity curves were obtained after SPECT images coregistration on a MRI masque. Specific volume of interest (SPE = SPEcific) were manually drawn on striatum, pons, thalamus and para-hippocampic gyrus including hippocampus; reference volumes of interest (REF = REFerence) were drawn on frontal and occipital cerebral cortex. On the basis of uptake kinetic, two modelisation approaches were considered: transient equilibrium model for reversible ligand (binding potential (BP) = (SPE ? REF)/REF) and Patlak graphical analysis for irreversible tracers (slope given by K_i/DV_ref where K_i is the influx contant and DV_ref is the distribution volume of the reference region). We observed an inflection or a stady state of the activity curves in the different regions studied between 250 and 1400 minutes, what seems to confirm that the tracer is little reversible. BP values obtained at 21 hours with occipital areas as reference and K_i/DV_ref values were respectively 4.62 ± 0.42 and 0.07 ± 0.01. The SPE classification according to BP and K_i/DV_ref values were similar to the classification according to the compartmental analysis (Kuhl 1994).The transient equilibrium model with late acquisition seems the more suitable because IBVM kinetic and practical simplicity of performing in clinical routine.