A G Smals

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Incubation of human testicular homogenates with [4-14C]pregnenolone gave substantial amounts of an unknown metabolite within 1 min, reaching plateau values of 17-23% of total radioactivity added within 5 min. Mass spectrometry of the metabolite showed it to be identical to the boar sex pheromone precursor androsta-5, 16-diene-3 beta-ol (ADL). In cell(More)
A 47-year-old man exhibited loss of libido and impotence in association with plasma hyperprolactinemia and a pituitary mass with downward extension of the tumor to the sphenoid sinus and to the suprasellar cisterns. Bromocriptine, 15 mg daily, reduced the hyperprolactinemia as well as tumor size. After 8 months on this therapy, the patient developed overt(More)
In human benign prostatic hyperplastic (BPH) tissue homogenates 5alpha-reduction of testosterone was examined at neutral pH. As Lineweaver-Burk and Eadie-Scatchard plots of estimated initial velocities against a wide range of substrate concentrations of 2 nM to 3.2 microM were non-linear, the existence of two 5alpha-reductase isozymes in this tissue was(More)
In concentrations probably exceeding those achieved in vivo, the cholesterol lowering compound simvastatin was found to suppress the synthesis of the androgens androstenediol and testosterone in vitro by human testicular homogenates. It was demonstrated that simvastatin in addition to its known inhibitory effect on HMG-CoA reductase activity, also affects(More)
The diagnostic accuracy of the corticotropin-releasing-hormone (CRH) test was compared with that of the oral high-dose dexamethasone suppression test in the differential diagnosis of Cushing's syndrome. A false-negative response to CRH was present in 9% (2 of 22) of patients with pituitary-dependent Cushing's disease and to high-dose dexamethasone in 11% (2(More)
The ACTH and cortisol responses to 100 micrograms ovine corticotropin-releasing hormone (CRH) in 19 consecutive patients with Cushing's disease were compared with those in 13 normal subjects. In 2 patients with Cushing's disease, plasma ACTH and cortisol did not increase after CRH administration. Compared to the normal subjects, maximal ACTH increments [135(More)
The metabolism of dihydrotestosterone (DHT) and 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-Adiol) was assessed in full homogenates of rat prostate and epididymis. The major degradational route of DHT was catalysed by the enzyme(s) 3 alpha-hydroxysteroid oxidoreductase (HSOR). Enzyme kinetic characteristics Vmax, Km and Vmax/Km ratio, were obtained(More)
Immunocytochemical studies and mRNA measurements have shown that the rat epididymis--like the rat prostate--expresses both rat steroid 5alpha-reductase isozymes, i.e. type I and II. So far, enzyme activity measurements in rat epididymis homogenates, however, do not support the presence of type I 5alpha-reductase activity. Incubating homogenates of both(More)
Reevaluating the assay for rat steroid 5 alpha-reductase isozymes in prostate and epididymis homogenates we encountered an extreme pH-dependency of the type II isozyme. The time-course of the metabolism of testosterone (T) to 17 beta-hydroxy-5 alpha-androstan-3-one (DHT) at acidic pH shows an initial burst when the homogenate is not brought to pH before the(More)