Androgenic expression in the submandibular gland of zinc-deficient mice.

The effects of zinc deficiency were studied in mice submandibular salivary glands (SMG). Zn-restricted mice (Zn-) were maintained from weaning until adult age (60 days) with a powdered diet containing 3 mg Zn2+/kg. Pair-fed animals (30 mg Zn2+/kg powdered diet) and control animals fed a regular pelleted diet were also used. Total protein content and proteolytic activity of SMG did not differ among the groups, but morphometric evaluations revealed significant alterations in the nucleus/cytoplasm size ratios, most likely due to an absolute reduction in nuclear volume (control = 122.5 +/- 6.4; Zn- = 91.6 +/- 10.5; pair-fed = 125.1 +/- 6.8 microns 3) paralleled by an increase of the height of the duct epithelium (control = 70.5 +/- 3.0; Zn- = 90.5 +/- 4.2; pair-fed = 81.7 +/- 3.0 microns). The altered food consistency could be responsible for these morphological changes. In order to assess the subcellular distribution of SMG androgen receptors in conditions of chronic Zn deficiency, Zn- animals were mated and the F1 generation was fed as their dams until the age of 45 days. Cytosolic (in 105,000 g supernatants) and nuclear (KCl-extracted) SMG receptors were determined with [3H]R1881. The Zn- animals had reduced nuclear/cytosolic ratios of androgen receptors (control = 0.62; Zn- = 0.14), as an indication that chronically deficient Zn intake determines a sort of destabilization of the interactions of androgen-receptor complexes with target cell nucleus.

Effects of zinc on the trophic activity of testosterone in androgen target tissues of castrate mice.

Swiss, 60-day castrate mice were injected with 0.5, 1.5 or 5.0 mg of testosterone propionate (TP; single dose, subcutaneously) 5 days before sacrifice, in order to investigate the ability of the submandibular gland (SMG) and other androgen target tissues to recover their normal morphology and function. Some animals were additionally injected intraperitoneally with ZnCl2 (0.14 or 0.28 mg Zn2+/animal per day) during the last 15 days before sacrifice. Only SMG tissue fully recovered by TP treatment. ZnCl2 significantly impaired the dose-dependent recovery of the granular ducts of mouse SMG tissue and that of other organs which display 'androgenic' (prostate, epididymis) and 'anabolic' responses (bulbocavernosus muscle). Histological examination of testes and epididymides of intact mice injected with ZnCl2 revealed abnormal spermatogenesis with multinucleated cells and acidophilic bodies within the tubular lumen; the circulating levels of testosterone in these animals were low. In vitro, Zn2+ inhibited androgen-binding activity in SMG cytosol, but the binding capacity increased in SMG of zinc-injected animals. It is suggested that zinc, although essential for the androgenic expression, is critical as far as its intracellular concentrations are concerned and that pharmacological doses of Zn2+ determine androgenic suppression by competition at receptor and acceptor levels.

Chronic administration of aqueous extract of Stevia rebaudiana (Bert.) Bertoni in rats: endocrine effects.

1. The effects of the active principles of S. rebaudiana (SR) on endocrine parameters of male rats were studied upon chronic administrations (60 days) of a concentrated, crude extract of its leaves, starting at prepubertal age (25-30 days old). 2. The following determinations were made: glycemia; serum levels of T3 and T4; available binding sites in thyroid hormone-binding proteins (T3R index); binding of [3H]R 1881 to prostate cytosol; zinc content in prostate, testis, submandibular salivary gland (SMG) and pancreas; water content in testis and prostate. The body weight gain and the final weight of testis, prostate, seminal vesicle, SMG and adrenal were also studied. 3. Results showed that the SR-treated group did not significantly differ from the control group, with exception to the seminal vesicle weight, which fell by about 60%. 4. It is concluded that if the SR extract does have some potential to decrease rat fertility at all, this effect is almost certainly not exerted on the male.