Substance P and microcirculation during stress

The experiments have been made on rats with the use of animals' immobilization on the back during 1 or 24 h as a stressor. Intravital study of the microcirculation in the rat mesentery has shown that P substance in a concentration of 7 X 10(-8) M aggravated the disturbances caused by the immobilization, while antiserum to P substance with an activity of 150 ng SP/equiv. normalized the microcirculation. The action of P substance and antiserum was similar as regards disturbances of vascular permeability for colloid carbon particles. It is concluded that P substance participates in the mechanisms of microcirculatory and vascular permeability disturbances during stress.     

Immobilization stress elevates IP(3) receptor mRNA in adult rat hearts in a glucocorticoid-dependent manner

Gene expression of the type 1 and 2 inositol 1,4,5-trisphosphate (IP(3)) receptors in the rat cardiac atria and ventricles and their possible modulation by single immobilization stress was studied. Single immobilization stress significantly elevated mRNA levels for both types of these receptors. To evaluate the involvement of glucocorticoids in the modulation of the gene expression of IP(3) receptors by immobilization stress, we used adrenalectomized and/or hypophysectomized rats. Since adrenalectomy and/or hypophysectomy completely abolished increase in IP(3) receptor's mRNA levels after the immobilization, we conclude that immobilization stress elevates mRNA of type 1 and 2 IP(3) receptors, mainly through the glucocorticoid responsive element.     

Growth hormone and drug metabolism. Acute effects on nuclear ribonucleic acid polymerase activity and chromatin.

Adult male rats, subjected either to sham operation or to hypophysectomy and adrenalectomy were maintained for 10 days before treatment with growth hormone. Results of the acute effects of growth hormone on the rat liver nuclear RNA polymerase I (nucleolar) and II (nucleoplasmic) activities as well as the chromatin template capacity were then studied and compared with the growth-hormone effects on the drug metabolism described in the preceding paper (Wilson & Spelsberg, 1976). 2. Conditions for isolation and storage of nuclei for maintenance of optimal polymerase activities are described. It is verified that the assays for polymerase activities require a DNA template, all four nucleoside triphosphates, and a bivalent cation, and that the acid-insoluble radioactive product represents RNA. Proof is presented that under high-salt conditions DNA-like RNA (polymerase II) is synthesized, and that under low-salt conditions in the presence of alpha-amanitin, rRNA (polymerase I) is synthesized. 3. In the livers of hypophysectomized/adrenalectomized rats, growth hormone increases the activity of both RNA polymerase enzymes and the chromatin template capacity within 1h after treatment. The effects last for 12h in the case of polymerase II but for only 6h in the case of polymerase I. Sham-operated rats respond to growth hormone in a manner somewhat similar to that shown by hypophysectomized/adrenalectomized rats. These results, which demonstrate an enhancement of RNA polymerase I activity in response to growth hormone, support those from other laboratories. 4. Growth-hormone enhancement of the chromatin template capacity in the liver of hypophysectomized/adrenalectomized rats contrasts with previous reports. The growth-hormone-induced de-repression of the chromatin DNA could represent the basis of the growth-hormone-induced enhancement of RNA polymerase II activity in the hypophysectomized/adrenalectomized rats, although some effect of growth-hormone on the polymerase enzymes is still suggested.     

The role of mast cells in vascular permeability disorders in rats subjected to immobilization stress]

Disturbances of vascular permeability were studied by the "vascular labeling" technique in the mesentry during the 24-hour immobilization of rats. Administration of dimebolin (an antihistaminic preparation) decreased the number of labeled vessels and labeling intensity. This effect was expressed in the presence of mast cells only and was accompanied by the mast cell degranulation. The authors suppose that the mast cells contain a substance preventing the disturbance of vascular permeability and released during degranulation. Such substance might be heparin. Experiments showed that small doses of heparin failed to produce such effect. These results allowed one to conclude that mast cells played a double role in the mechanisms of disturbance of vascular permeability during immobilization--the damaging (by the action of histamine and serotonine) and the protective (by the released heparin) action.     

Hypophysectomy Prevents Ghrelin-Induced Adiposity and Increases Gastric Ghrelin Secretion in Rats

Objective: The novel gastric hormone ghrelin has recently been identified as an important modulator of energy homeostasis. Leptin-responsive hypothalamic neuropeptide Y/Agouti-related protein neurons are believed to mediate afferent ghrelin signals. Little is known, however, about ghrelin-induced efferent signals. We therefore investigated if hypothalamic-pituitary axes have a role in transferring ghrelin-induced changes of energy balance to the periphery. Research Methods and Procedures: We subcutaneously injected hypophysectomized, as well as adrenalectomized, thyroidectomized, and sham-operated control rats with GH secretagogues [ghrelin, growth hormone (GH)-releasing peptide] for 1 week. Body weight, food intake, and body composition (chemical carcass analysis) were analyzed and compared with vehicle-treated controls. In addition, we quantified circulating levels of endogenous ghrelin in hypophysectomized and GH–treated normal rats. Results: GH-secretagogue treatment of sham-operated control rats dose-proportionally increased food intake, body weight, and fat mass compared with vehicle-injected controls (p < 0.01). These effects, however, were not observed in ghrelin-treated hypophysectomized, thyroidectomized, or adrenalectomized rats, indicating an essential role for the pituitary axis in ghrelin-induced adiposity. Circulating levels of endogenous ghrelin were reduced by administration of GH in normal rats and were about 3-fold higher in hypophysectomized rats (n = 20, p = 0.001), suggesting a regulatory feedback loop involving the stomach and the pituitary to regulate gastric ghrelin secretion. Discussion: According to these results, the endocrine pituitary is mediating ghrelin-induced changes toward a positive energy balance and is involved in the regulation of ghrelin secretion through a gastro-hypophyseal feedback loop.     

Effect of adrenalectomy on distal tubule water permeability of the Brattleboro rat

The mechanism of impaired water excretion in adrenalectomized mammals is unclear. Previous workers have suggested that one cause might be increased water permeability of the distal nephron, allowing back diffusion of water from tubular fluid diluted by the ascending limb. Evidence to support this mechanism in previous studies has been confounded by simultaneous changes in steroid and antidiuretic hormone levels. We compared osmotic and diffusional water permeability of the surface late distal tubule in vivo in intact and adrenalectomized Brattleboro rats, which are free of antidiuretic hormone. The adrenalectomized rats were demonstrated to have impaired diluting capacity in clearance studies. Adrenalectomized rats had a sixfold increase in osmotic permeability and a 1.5-fold increase in diffusional permeability over intact controls. Adrenal steroids have a specific action on water permeability of the distal nephron, independent of antidiuretic hormone.     

Role of sulfhydryls and early vascular lesions in gastric mucosal injury

This paper reviews the recently discovered role of sulfhydryls and early vascular injury in the pathogenesis of acute gastric mucosal injury. In the rat ethanol caused a dose-dependent decrease in nonprotein sulfhydryl concentration in the gastric mucosa within 1-5 min following an intragastric dose. These biochemical changes were accompanied by increased vascular permeability in the glandular stomach as revealed by the measurement of extravasated Evans blue injected i.v. prior to the administration of ethanol. Morphologic evidence of vascular injury was provided by labelling of damaged blood vessels in the stomach following the i.v. administration of colloidal particles in the form of india ink or monastral blue. The functional and structural damage to capillaries and venules in the glandular stomach was also maximal within 1-6 min after 1 ml of 75 or 100% ethanol given orally. Pretreatment with sulfhydryl (SH) containing drugs (e.g., L-cysteine, N-acetyl-L-cysteine, cysteamine, dimercaprol) or prostaglandin (PG) F2 beta prevented the ethanol-induced increase in vascular permeability, the labelling of blood vessels with vascular tracers, and the subsequent haemorrhagic erosions. The desquamation of superficial epithelial cells, however, was not markedly modified by either SH or PG compounds. This organoprotective effect of SH and PG drugs was virtually counteracted in adrenalectomized rats that exhibited "vascular fragility". Glucocorticoid treatment restored the response of adrenalectomized animals. Thus, a SH- and glucocorticoid-sensitive early vascular injury seems to be of major significance in the pathogenesis of haemorrhagic gastric erosions and SH-containing compounds represent a new group of cytoprotective or organoprotective agents.     

Effects of SP1-11 and its N-terminal fragment SP1-4 on several indices of the microcirculatory system in stress]

In the experiments on rats it was shown that 5-hour immobilization induced the disturbances of terminal blood flow, degranulation of mast cells, increase of venular permeability and contractile activity of lymphaticus. I/p injection SP1-11 (125 micrograms/kg) before stress aggravated the disturbances caused by immobilization. The prophylactic i/p injection SP1-4 induced tranquilizing (100%), sedative (30%) or narcosis (20%) effect. In the rats with sedative or narcosis effects the relative normalization of components of microcirculatory system was observed.     

Plasma corticoids and brain tryptophan after acute and tolerance dosage of LSD.

The effect of acute and tolerance dosage schedules of LSD on plasma corticoids and brain tryptophan in normal, adrenalectomized and hypophysectomized rats was examined. Plasma corticoids increased 20-fold after one dose of LSD and the time course of this effect paralleled the increase in brain tryptophan. Both effects of LSD were abolished in adrenalectomized animals; after hypophysectomy the drug-induced tryptophan increase did occur but only after a significant delay. After multiple daily injections of LSD there was a significant degree of tolerance both to the plasma corticoid and brain trytophan response.     

Divergence of growth hormone actions on hepatic drug metabolism in the presence and absence of the pituitary gland.

Experiments were carried out to compare the effects of growth hormone on hepatic drug oxidation in normal and hypophysectomized rats. Administration of growth hormone to normal male rats lowered hepatic microsomal cytochrome P-450 content and decreased the rates of ethylmorphine n-demethylation and aniline hydroxylation. These effects were fully manifested in orchiectomized or adrenalectomized males, excluding a dependence upon endogenous steroids. Growth hormone was without effect on hepatic drug metabolism or cytochrome P-450 content in normal female rats. In contrast to its actions in animals with intact pituitary glands, administration of growth hormone to hypophysectomized rats of either sex increased the rate of ethylmorphine metabolism. Furthermore, in both males and females, aniline hydroxylation and microsomal cytochrome P-450 content were unaffected by growth hormone in the absence of the pituitary gland. Prolactin administration did not affect hypophysectomized or in normal rats of either sex. The results indicate that the nature of growth hormone actions on hepatic drug oxidation is pituitary-dependent and probably intertwined with the effects of other hormones. Furthermore, the direct physiological effects of growth hormone on hepatic mixed function oxidases seem to depend upon the substrate employed.     

Dynamics of microcirculatory system recovery in the post-stress period

Twenty-four-hour immobilization or electric stimulation for 6 h were used in rats as stressors. The first stressor caused more profound and protracted disturbances in the microcirculatory system. The recovery of the microcirculation occurred in 50% of animals by day 6 and in 100% by day 14 after immobilization. The terminal blood flow recovery after 6-hour electric stimulation was seen in a day. Vascular permeability after 24-hour immobilization returned to normal in 24 h, and after 6 h of electric stimulation in 6 h. This process correlated with the morphofunctional status of mast cells and was probably phasic in nature.     

Adrenal gland modulates oestrogen requirement for implantation in the rat

The effect of adrenal steroids upon implantation was evaluated by examining the efficacy of oestradiol-17 beta on the initiation of implantation in ovariectomized, ovariectomized plus adrenalectomized or hypophysectomized pregnant rats treated with progesterone. More oestrogen (X 5) was required in ovariectomized animals to obtain results equivalent to those obtained with the other animal models.     

A MODULATING ROLE OF PITUITARY-ADRENAL AXIS IN CEREBRAL METABOLISM OF ADENOSINE 3'',5''-MONOPHOSPHATE

Abstract— The effect of adrenalectomy or hypophysectomy on the metabolism of adenosine 3',5'-monophosphate (cyclic AMP) in the cerebral cortex of male Wistar rats was investigated.
The bilateral removal of adrenal glands reduced significantly the activity of cerebral adenylate cyclase [EC 4.6.1.1]. whereas that of cyclic 3'.5'-nucleotide phosphodiesterase [EC 3.1.4.17] remained unchanged. The formation of cyclic AMP measured in cerebral cortical slices from adrenalectomized or hypophysectomized rats was also diminished. Decreases in the activity of adenylate cyclase and formation of cyclic AMP following adrenalectomy were antagonized by in vivo administration of dexamethasone or aldosterone, while those observed in hypophysectomized rats were restored by ACTH or dexamethasone. It is suggested that the pituitary adrenal axis has a modulating role in the metabolism of cerebral cyclic AMP, possibly by changing adenylate cyclase activity.     

Morphometric investigations into the mechanism of the compensatory hypertrophy of the rat adrenal zona fasciculata after unilateral adrenalectomy

Summary Compensatory hypertrophy of the remaining gland in unilaterally adrenalectomized rats was investigated by morphometric techniques. It was observed that compensatory adrenal growth occurred in both dexamethasone-treated and hypophysectomized rats, receiving maintenance doses of ACTH. However, it was only half that found in intact animals. These results support the view that activation of the hypothalamo-hypophyseal axis is not the unique mechanism underlying adrenal compensatory hypertrophy in the rat.     

Incorporation of methionine-35S into the structure of the brain at different pituitary-adrenal system hormone levels

The rate of 35S-methionine incorporation into the anterior and posterior hypothalamus, tonsil and hippocamp was studied in experiments on intact, adrenalectomized, and hypophysectomized rats as well as in those exposed to ACTH or dexamethasone. A conclusion is drawn that ACTH and glucocorticoids exert a dissimilar and non-equivalent effect on the brain structures responsible for the activity displayed by the hypophyseal-adrenal system.     

Behavioral effects of L-tryptophan and p-chlorophenylalanine after adrenalectomy or dexamethasone administration in rats

Effects of acute administration of L-tryptophan (L-TRP. 250.0 mg/kg, i.p.) on active avoidance conditioning and "open-field" behavior were studied in male rats after adrenalectomy of dexamethasone administration. L-TRP inhibited the acquisition and reproduction of active avoidance reaction in adrenalectomized and dexamethasone-treated rats. Moreover, L-TRP decreased horizontal locomotor activity and grooming behavior in the "open field" on adrenalectomized rats. On the contrary, p-CPA restored the active avoidance conditioning in adrenalectomized rats and rats with excess of glucocorticoids. Also, p-CPA increased the total locomotor activity and grooming behavior in the "open field" in adrenalectomized rats, but decreased horizontal locomotor activity and enhanced emotional reaction in dexamethasone-treated rats in the "open field".     

The changes of in vitro 131I-iodine uptake in the thyroid gland of rats exposed to septal lesions and immobilization stress.

The in vitro uptake of 131I by the thyroid gland was investigated in rats after immobilization stress with special respect to animals lesioned in the septal area. Lesions in a septal area performed 10 days before decreased the iodide accumulation in the thyroid, while stress by immobilization increased it to the control basal value. Repeated immobilization in control rats did not produce any changes in the iodide uptake in vitro. ACTH injected in vivo stimulated the iodide 131I uptake in vitro by thyroid glands of hypophysectomized rats. It is concluded that immobilization stress in rats with septal lesions increases 131I-iodide uptake in vitro and that the increase was probably influenced by both catecholamines and glucocorticoids.     

Nutrition of Threonine

By administering 2 mg/day of cortisone acetate to adrenalectomized rats, the hepatic threonine dehydratase activity of these rats increased 5 times as much as that of the control. By administering 5 IU/day of ACTH to hypophysectomized rats, both the hepatic threonine dehydratase activity and the adrenal glucose-6-phosphate dehydrogenase activity increased 3 times and 7 times as much as that of the control group, respectively. The effects of excess feeding of lysine or threonine on the increase of the dehydratase activity by the adminitration of cortisone to the adrenalectomized rats and the administration of ACTH to the hypophysetomized rats were negative. When the intact rats were fed on lysine and/or threonine excess diet, the amount of glucocorticoid secretion as measured by the adrenal glucose-6-phosphate dehydrogenase activity increased and the hepatic threonine dehydratase activity increased accordingly. A linear relationship was found between these two activities and no significant deviation from the relationship due to the difference in diet composition was observed. A mechanism was proposed, based on these results, explaining the fact that the hepatic threonine dehydratase activity increased when rats were fed on lysine or threonine excess diet.     

Effects of desensitization of capsaicin-sensitive afferent neurons on gastric microcirculation in rats depend on the blood glucocorticoid hormone level

The effects of desensitization of capsaicin-sensitive afferent neurons on gastric microcirculation were investigated before and after administration of indomethacin at ulcerogenic dose in adrenalectomized rats with or without corticosterone replacement and in sham-operated animals. We estimated the blood flow velocity in submucosal microvessels; the diameters and permeability of mucosal venous microvessels as parameters of gastric microcirculation. Desensitization of capsaicin-sensitive neurons was performed with capsaicin at the dose 100 mg/kg two weeks before the experiment. Adrenalectomy was created one week before experiment. In vivo microscopy technique for the direct visualization of gastric microcirculation and the analysis of the blood flow was employed. Indomethacin at ulcerogenic dose decreased the blood flow velocity in submucosal microvessels, caused dilatation of superficial mucosal microvessels and increased their permeability. Desensitization of capsaicin-sensitive afferent neurons potentiated indomethacin-induced microvascular disturbances in gastric submucosa-mucosa. These potentiated effects of the desensitization are obviously promoted by concomitant glucocorticoid deficiency. Thus, glucocorticoid hormones have a beneficial effect on gastric microcirculation in rats with desensitization of capsaicin-sensitive afferent neurons.     

The paraventriculo-infundibular corticotropin releasing factor (CRF) pathway as revealed by immunocytochemistry in long-term hypophysectomized or adrenalectomized rats

The immunocytochemical localization of corticotropin releasing factor (CRF)-containing pathways projecting from the paraventricular nucleus (PVN) to the external layer of the median eminence (ME) in long-term hypophysectomized or adrenalectomized rats is described. Immunocytochemistry was followed by silver intensification of the diaminobenzidine end-product. In comparison with untreated control rats, both hypophysectomy and adrenalectomy resulted in a dramatic increase in immunostaining of the CRF-containing perikarya and fibers, particularly those originating from the PVN and terminating in the ME. The staining was more intense in adrenalectomized than in hypophysectomized rats. The CRF-positive fibers emerging from the PVN form a medial, an intermediate and a lateral fiber pathway. The lateral and intermediate CRF tracts leave the dorsolateral part of the PVN and course laterally and medially of the fornix, respectively, then ventrally toward the optic tract. Just dorsal to the optic tract they turn in caudal direction and run parallel with and very close to the basal surface of the hypothalamus; individual fibers then turn medially to terminate in the external layer of the ME. Only a few fibers originate from the medial-ventral part of the PVN (medial pathway). These fibers run in ventral direction along the walls of the 3rd ventricle and terminate in the ME. Thus the majority of CRF fibers, similarly to other peptidergic systems, reach the medial basal hypothalamus from the anterolateral direction.