Cyclic nucleotide phosphodiesterase activity in rat adrenal gland zones

The distribution of cyclic 3′, 5′ -nucleotide phosphodiesterase activity in the rat adrenal gland has been studied. Phosphodiesterase activity was 10-fold higher in the zona glomerulosa than in the zona fasciculata-reticularis. Kinetic studies carried out at low substrate concentrations suggest the possible presence of multiple forms of phosphodiesterase activity in both zones of the adrenal; however, these forms appear to have similar apparent Km's for cAMP. Thus, the well known differences in the steroidogenic response of the two zones to ACTH stimulation may be partially explained by large differences in total activities of the various forms of phosphodiesterase.     

Effect of pectin feeding on monocarboxylate transporters in rat adrenal gland

We have recently proved the expression and localization of seven monocarboxylate transporters (MCT1, MCT2, MCT3, MCT4, MCT5, MCT7, and MCT8) in the rat adrenal gland. So far, there are no data reporting possible regulation of any MCT isoform in the adrenal gland. Pectin is a soluble dietary fiber that is known to exert a hypocholesterolemic effect and increases the short chain fatty acids production in the large intestine. This work aimed to study the effect of pectin feeding on the expression of MCTs (MCT1–MCT5, MCT7, and MCT8) and their cellular distribution in rat adrenal gland. Western blotting demonstrated significant increase in the expression levels of MCT1, MCT2, MCT4, MCT5, and MCT7 in pectin-fed rats in comparison with the controls. Immunohistochemistry revealed extended distribution and distinctive increase in the immunoreactivities of MCT1, MCT2, MCT4, MCT5, and MCT7 in the adrenal cortical zones, besides the increase in the immunoreactive intensity of MCT5 and MCT7 in the adrenal medulla of pectin-fed versus control rats. Interestingly, zona glomerulosa which did not show any reactivity for MCT1 or MCT2 in controls, exhibited marked immunopositivities for both MCT1 and MCT2 in pectin-fed rats. MCT3 and MCT8, however, did not show significant changes in their expression levels between pectin-fed and control rats. Our data is the first to describe the up regulation of various MCTs in rat adrenal gland under the influence of pectin feeding. This up regulation might be a compensatory response to the hypocholesterolemic effect of pectin in order to maximize the intracellular availability of acetate. This article suggests that monocarboxylate transporters have an important physiological role in the regulation of adrenal hormones as well as in cholesterol homeostasis.     

Effect of clonidine on second messenger systems in rat adrenal gland.

Clonidine, an alpha 2-adrenergic agonist, also binds to non-adrenergic imidazole receptors in brain and peripheral tissues. In adrenal medulla, however, clonidine appears to bind only to imidazole receptors. To assess whether the signal transduction mechanism of imidazole receptors differs from alpha 2-adrenergic receptors, we studied the actions of clonidine on the turnover of phosphoinositide and the production of cAMP and cGMP in slices of rat adrenal gland. Clonidine did not modify basal or carbachol mediated increases in phosphoinositide turnover or production of cAMP, however it increased the production of cGMP. The increase in cGMP was slow and unaffected by the addition of the phosphodiesterase inhibitor, IBMX. We conclude that the second messenger response triggered by clonidine in adrenal differs from that usually coupled to alpha 2-adrenergic receptors. Whether the effect is mediated by cell surface imidazole receptors remains to be established.     

Influence of air ions on brain activity induced by electrical stimulation in the rat

The brain induced activity was studied in 18 rats wearing chronically skull implanted electrodes. The stimulating factor was various electrical stimulations of the mesencephalic reticular activating formation, given during the slow wave state of sleep. The results of 300 stimulations were measured by amplitude and frequency changes in the EEG simultaneously recorded. Animals previously exposed to positive air ions (3 weeks 80,000 ions/ml) exhibited lowered excitability of the reticulocortical system. Significantly higher stimulations were necessary to induce arousal. Negative air ions induced more intricate effects: brain excitability was lowered when tested with weak stimulations, but normal when evaluated with medium high level stimilations. Sleep seems first more stable but as stimulation increases, arousal is soon as effective as in controls. These results are in agreement with others findings in behavioral fields and partly explains them.     

Oestrogen receptors in the rat adrenal gland

Cytosol from the adrenal gland of male and female rats contains a specific binding protein for oestradiol-17β. This protein has all the characteristics of a cytoplasmic oestrogen receptor. It is excluded by Sephadex G-200 gel filtration, has a sedimentation coefficient of 8–9 S by sucrose density gradient centrifugation in low salt and dissociates into a 4 S form by centrifugation in high salt (0.5 M KCl). The binding protein is heat sensitive and oestradiol-17β binding is eliminated by protease and by sulphydryl blocking reagents (2mM p-chloromercuriphenylsulphonate). The bound oestradiol dissociates very slowly at 0°C. The adrenal oestrogen receptors have a very high affinity for oestradiol-17β, but lower affinity for oestradiol-17α and do not bind testosterone, androstene-3,17-dione or corticosterone. Scatchard analysis of the saturation data for oestradiol revealed one class of high affinity binding sites with an apparent equilibrium constant of dissociation K_D at 0°C of 5.8 × 10⁻¹⁰M. The number of binding sites was calculated to be 70 fmol/mg cytosol protein. Cytosol fractions from androgen insensitive (tfm) male rats contain oestrogen receptors in amounts very similar to that of the normal littermates.     

Sex-dependent effect of melatonin on the secretory activity of rat and hamster adrenal gland in vitro

Adrenal quarters from adult male or female hamsters were incubated in the presence of melatonin (10(-7) or 10(-4)M), and cortisol concentration in the incubation medium was assayed by RIA. Melatonin did not change cortisol output by adrenals obtained from the male hamsters, while a slight stimulatory effect was observed in female glands, the lower concentration of melatonin being more effective than the higher one. At both concentrations tested, melatonin notably stimulated corticosterone output by isolated rat adrenocortical cells derived from the males, and lowered corticosterone secretion by the cells obtained from the female glands only at a concentration of 10(-7) M. The lower concentration of melatonin increased ACTH (0.1 mU.ml-1)-stimulated corticosterone output by the cells of male and female rat adrenals. The pineal hormone was ineffective at a concentration of 10(-4) M, as well as in the presence of a higher dose of ACTH (1.0 mU.ml-1). These findings indicate a distinct sex-dependent effect of melatonin on in vitro cortisol and corticosterone production, and demonstrate that the modulatory effect of melatonin of the secretion of steroid hormones is more effective at lower concentrations.     

Nestin expression in rat adrenal gland

The constituents of the intermediate filament network of adrenal gland cells have not been deeply investigated in vivo. Adrenocortical cells have been reported to express cytokeratins and vimentin, but the intermediate filament components of the adrenomedullary cells are still unknown. Nestin is an intermediate filament protein that is mainly expressed in the developing nervous and muscle systems. It has been reported to be unable to form filaments by itself and it co-assembles with vimentin. Using immunocytochemical and biochemical approaches, the present study demonstrates that nestin is expressed in situ either in the cortex or in the medulla of adult rat adrenal glands. Nestin-negative cells prevalently form the zona glomerulosa whereas the zona fasciculata and the zona reticularis are mainly nestin-immunoreactive. Nestin-positive cells always express vimentin-like immunoreactivity but several cells apparently expressing only vimentin are detectable too. Nestin is also expressed by adrenomedullary cells that also display a faint vimentin-like immunoreactivity. We hypothesise that the inconstant detection of nestin in adrenocortical cells depends on their different functional moments. Moreover, even though our data do not allow to confirm vimentin in adrenomedullary cells, in situ detection of nestin in the adrenal medulla indirectly supports in vivo expression of vimentin in chromaffin cells.     

Effect of stress on postnatal growth in weight of rat body and adrenal gland

Seven-week male Wistar rats weighing 145-155 g were housed 10 (control) or 20 (crowded) per cage (50 x 35 x 15 cm). Groups of control and crowded animals were decapitated within 0.5, 1, 3, 7, 14, 21, 28, 35, 56, 70, and 98 days of experiment. The keeping of rats in crowding conditions induced chronic stress, which developed, according to phase changes in plasma concentration of corticosterone and adrenal content of cholesterol, through the stages alarm, resistance, and exhaustion. The postnatal growth of body weight in the stressed rats was behind that in the control. Under the crowding conditions, the adrenal weight did not undergo significant increase, since the stress-induced hypertrophy of the zona fasciculata was compensated by the proportional suppression of the postnatal growth of the zona reticularis. After 56 days, the postnatal growth of the hypertrophied fascicular zone was delayed in the experimental rats.     

Some effects of air ions on the activity of rats

A duct system was arranged through which flowed air of controlled ion concentration. In series was a chamber with a flexible dielectric floor which made possible electrical detection of activity.Exposure to various ion concentrations of either polarity produced pronounced effects.In addition to gross motor activity six other behavioural parameters were recorded. The lowest ion concentration were most effective. In addition to presenting a controlled ambient ion concertration the ion current drawn by the animal was measured. This varied markedly from rat to rat.

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Zusammenfassung Ein Kanalsystem zum Durchfluss von Luft bekannter Ionenkonzentration wurde eingerichtet. Angeschlossen war eine Kammer mit einem beweglichen dielektrischen Boden, der die Registrierung der Aktivität von Ratten ermöglichte. Neben der motorischen Aktivität wurden 6 andere Verhaltensformen der Tiere registriert.Die niedrigste Ionenkonzentration war am wirksamsten zur Anregung der Aktivität. Neben der Ionenkonzentration in der Kammer wurde der von den Tieren eingeatmete Ionenstrom gemessen; er variierte stark von Tier zu Tier.

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Resume On a construit un canal dans lequel il est possible de faire circuler de l'air dont la concentration en ions est contrôlable. On y a adjoint une cellule dont le sol est constitué par un diélectrique flexible permettant de déceler électriquement l'activité de petits animaux.En exposant des rats à des concentrations ioniques variables et de polarité différente, on peut constater des effets prononcés sur le comportement des animaux. En effet, en plus de l'activité motrice, on a enregistré six autres formes de ce comportement. Ce sont les plus faibles concentrations qui produisent le plus d'effets. A part la concentration en ions à l'intérieur de la cellule, on a également mesuré la quantité d'ions absorbés par les bêtes par voie respiratoire. Cette quantité varie fortement d'un individu à l'autre.

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This work was supported by Public Health Service Research Grant #AP00305-02 from the Division of Air Pollution, Bureau of State Services and also by a grant from the Atmospheric Science Research Center of the State University of New York.