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.

Circulating thyroid hormone levels in young pregnant rats and their fetuses: effect of malnutrition.

In order to evaluate some factors likely to be involved in the maternal and fetal growth impairment due to alimentary protein deficiency, the circulating levels of triiodothyronine (T3) and thyroxine (T4) were studied in 4 young (45-day-old) female rat groups: control and malnourished, both nonpregnant and pregnant; similarly scheduled groups were studied using adult (100-day-old) rats. Circulating levels of T4 were higher in nonpregnant, malnourished young rats than in their corresponding controls. T3 levels were higher in young malnourished animals and lower in adult malnourished animals, nonpregnant or pregnant, as compared to controls. Pups from young malnourished mothers showed significantly lower birth weights than those from controls. The present results suggest that there are age differences in thyroid function, as affected by protein-calorie malnutrition in pregnant and nonpregnant rats. On the other hand, the circulating thyroid hormone levels were not importantly affected by the mother dietary protein restriction under our experimental conditions.

Thyroidal modulation of androgenic expression in mice submandibular gland.

We investigated the influence of testes and thyroid gland on the maintenance of biochemical parameters and of [3H]R1881 binding sites of adult mice submandibular gland (SMG). Castration (Cx) performed at beginning of puberty prevented sex-dependent SMG development without interfering with maximal androgen binding capacity. Thyroidectomy (Tx) had strong effects on SMG, mainly by lowering the number of androgen binding sites. All alterations could be fully reverted after treatment with testosterone (5 mg/animal, single dose) or with thyroxine (T4, 250 micrograms/animal per day during 5 days). The effects of Cx on SMG could be reverted by therapy with testosterone, T4, or with both hormones (testosterone + T4) in a non-synergistic fashion. It is shown the importance of thyroidal activity on the physiological maintenance of androgen receptors in the murine SMG; the role played by thyroid gland seems to be essential for the full expression of the androgen-dependent SMG activity in adult mice.

Protein-calorie malnutrition in the young pregnant rat: factors involved in fetal growth impairment.

Factors involved in fetal growth retardation as seen in pups of protein-deprived young rats are examined. Young (50 to 55-day old) and adult (90 to 100-day old) rats were fed a diet of low (6%) or normal (25%) protein content during pregnancy. Dams and neonates were killed soon after parturition. Young malnourished dams showed a significant reduction in circulating glucose levels while their pups had significantly lower birth weights and circulating glucose and insulin levels than those of young control mothers. Such alterations were not seen in adult animals. Maternal malnutrition did not affect circulating levels of thyroxine in the neonates. These data indicate that maternal hypoglycemia may play an important role in determining blood glucose and insulin reduction and, consequently, the low birth weight seen in pups of young malnourished rats.

Ontogenesis of androgen receptors in the mouse submandibular gland: correlation with the developmental profiles of circulating thyroid and testicular hormones.

Specific binding of the synthetic androgen, [17 alpha-methyl-3H]methyltrienolone, to the cytosol fraction of the submandibular salivary gland (SMG) of male mice was studied in relation to the developmental profiles of testosterone and thyroid hormones in blood. The peak rise of serum triiodothyronine (T3) at prepubertal age was closely related to both the increase of maximal androgen-binding capacity in SMG and the conspicuous surge of proliferative activity as indicated by increased rate of glandular DNA content. Also, 2-month thyroidectomized mice had an age-related, strong reduction in the number of androgen-binding sites. On the other hand, the development of the secretory functions of the gland could be better related to the rise of circulating testosterone by days 25-30 of age. The results suggest that thyroid hormones play a very important role in the early induction and further maintenance of androgen receptors in the murine SMG.

Differential actions of testosterone and its metabolites on mice submandibular gland.

Submandibular glands from male mice castrated at 21 days of age and killed 60 days thereafter exhibited impaired development of the granular ducts (GD), an effect which is directly related to its androgen-dependent feature. Testosterone and other related steroids of natural occurrence were given to these animals in order to determine the mechanism by which those compounds bring about recovery of their glandular histophysiology. The size and number of GD were reconstituted by the steroids in the following order of potency: 5 alpha-androstane-3 alpha, 17 beta-diol greater than testosterone propionate greater than 5 alpha-dihydrotestosterone greater than or equal to testosterone greater than 5 alpha-androstane-3 beta, 17 beta-diol. All of the drugs stimulated protein synthesis, but only 3 alpha-diol was also able to increase DNA synthesis. Results support the assumption that 3 alpha-diol exerts both proliferative and hypertrophic effects on mice SMG, possibly through some receptor-independent pathway(s); the action of the other steroids is essentially hypertrophic in nature.

Pituitary-testicular axis abnormalities in immature male hypothyroid rats.

The pituitary-testicular disturbances which follow the onset of hypothyroidism were studied in immature male Wistar rats rendered hypothyroid by treatment with methimazole (MMI) given in drinking water, starting at 40 days of age. Half of the animals continued on MMI (MMI group) up to 140 days of age; the remaining rats were withdrawn MMI at 100 days and injected thereafter s.c. with 3 micrograms of T3 daily, during the last 40 days (MMI + T3 group). Ten rats were used as controls (C group). Hypothyroidism induced in immature animals significantly decreased serum T4, T3, LH, PRL, and testosterone levels, and also impaired the normal growth of body and sex accessory glands. T3 replacement therapy helped to normalize serum hormonal levels, but the body and sex accessory gland weights were not fully corrected. Hypothyroidism also reduced the [125I]LH/hCG binding sites of testicular homogenates. T3 replacement was not able to improve the binding; nonetheless, the hormone-receptor affinity constant remained unaltered among the groups. Leydig cell responsiveness to hCG stimulation in vitro (0-82 nM) showed impaired testosterone production in the MMI group (25% of that found in the C group) and also in the MMI + T3 group (80% of that found in the C group). These data demonstrate that induction of hypothyroidism in the immature male rat leads to alterations in serum LH, PRL and testosterone levels, and suggest that thyroid hormones have a modulating action on the testis as far as LH-mediated testosterone secretion is concerned.

Beta-adrenergic stimulation of mouse parotid gland: amylase activity and secretory granules during isoproterenol-induced mitosis.

This paper examines the mitotic activity of parotid glands of groups of mice sacrificed at 1 hr-intervals between 26 and 36 hr after being injected with dl-isoproterenol (IPR, 1 mumol/g, single dose, i.p.). Maximal mitotic activity occurs 35 hr after IPR injection; there is a concomitant rise of amylase activity (64% over control). Mitotic cells showed increased number of secretory granules (N) with regard to interphasic cells. However, the increment of N is paralleled by an increment of the cell section area (A); the N/A ratio is thus maintained around 0.45 throughout. These findings suggest that during IPR-induced mitosis of mice parotid cells there is not a blockade of the biosynthetic pathways which lead to the appearance of secretory granules in the cell cytoplasm.

Effects of testosterone and its metabolites in relation to androgen-binding activity in murine submandibular salivary glands.

The relative potencies of testosterone (T), testosterone propionate (TP) and other related steroids (5 alpha-dihydrotestosterone, DHT; 5 alpha-androstane-3 alpha, 17 beta-diol, alpha-diol; 5 alpha-androstane-3 beta, 17 beta-diol, beta-diol) in restoring some morphological and functional characteristics of submandibular gland (SMG) were investigated in castrated mice. The steroids restored to near-control values the glandular weight and total protein content, alpha-diol and TP being the most effective compounds tested; with regard to proteolytic activity stimulation, beta-diol was more effective than DHT. The alpha-diol metabolite was unique in significantly increasing DNA synthesis. In competition studies, alpha-diol and beta-diol were ineffective in displacing the specifically bound [3H]-R1881 from the SMG androgen-binding macromolecules. Thus T can elicit its effects on SMG without the need of prior conversion to DHT; there must be alternative, receptor-independent mechanisms whereby alpha- and beta-diol exert trophic/metabolic effects on murine SMG.

Maternal and fetal liver enzymes of mid-to-term pregnant rats chronically treated with magnesium sulphate.

1. Pregnant rats were injected daily with 150 mg/kg body weight magnesium sulphate (MgSO4) starting at the 5th day of gestation and sacrificed at the 13th, 15th, 19th or 21st day of pregnancy. 2. Maternal liver enzymes of glycolysis (HK, PFK, PK, LDH), pentose shunt pathway (G-6-PD) and glutamate metabolism (Ala-T, Asp-T) were unaltered by the treatment. 3. Fetal liver PK, LDH, G-6-PD, Ala-T and Asp-T activities were strongly activated by MgSO4 to levels in some instances as high or even higher than those found in the adult rat liver. 4. Results support recent evidence that MgSO4 induces precocious maturation of certain morphofunctional features of the fetal rat liver. 5. Data presented herein cannot account for the strong deleterious effects of the drug on rat pregnancy. Instead, such effects would be better explained by the direct cell toxicity of MgSO4.

Nuclear androgen receptors in prostates from diabetic rats.

It is shown that the binding of the synthetic androgen [3H] methyltrienolone ([3H] R1881) to the nuclear fraction of prostates of streptozotocin-diabetic rats is 38% reduced in comparison to controls. Although the exogenous replacement therapy of diabetic animals wih insulin was capable of restoring to normality several body and tissue parameters, the androgen binding capacity of prostate nuclei is not recovered. Normal binding values were observed in diabetic animals which have been treated with exogenous testosterone. It is postulated that the decrease in the nuclear androgen receptor content in the prostatic gland of streptozotocin-diabetic rats is due to the lower circulating testosterone levels in these animals.

Patterns of mid-to-term placental enzymes in rats treated with magnesium sulphate.

1. Pregnant rats were injected daily with 150 mg/kg b.w. of magnesium sulphate (MgSO4) starting at the 5th day gestation and sacrificed at the 13th, 15th, 19th or the 21st day of pregnancy. 2. The profiles of LDH, G-6-PD, HK and Ala-T activities in mid-to-term placentae were not changed by the drug. 3. Placental PK was strongly activated by MgSO4 in 13-19 day pregnant rats, whereas Asp-T was more severely depressed at the final phase of pregnancy. 4. Although mild to moderate changes in the flow of substrates should be predictable by the results, it seems unlikely that these could account for the reported deleterious effects of MgSO4 on rat offsprings.

Distribution and kinetics of hippuran 131I in rats.

A six-compartment model is proposed to study hippuran kinetics in several tissues and body fluids. This comprises plasma (in which the tracer is introduced), extravascular space (anatomically not defined), kidneys (left and right), "delay" (the dead space through which the urine passes from kidneys to the bladder) and the cumulative urinary excretion. Based on accurate internal measurements of radioactivity, theoretical values which reproduced the experimental data have been fitted to a SAAM program. A good fit was observed between the curves. This study is intended to be of value for better understanding and use of tests for clinical evaluation of renal function.

Distribution and kinetics of hippuran 131I in rats.

A six-compartment model is proposed to study hippuran kinetics in several tissues and body fluids. This comprises plasma (in which the tracer is introduced), extravascular space (anatomically not defined), kidneys (left and right), [quot ]delay[quot ] (the dead space through which the urine passes from kidneys to the bladder) and the cumulative urinary excretion. Based on accurate internal measurements of radioactivity, theoretical values which reproduced the experimental data have been fitted to a SAAM program. A good fit was observed between the curves. This study is intended to be of value for better understanding and use of tests for clinical evaluation of renal function.