Effects of CP 55,940 — agonist of CB1 cannabinoid receptors on ghrelin and somatostatin producing cells in the rat pancreas

Cannabinoids participate in the modulation of numerous functions in the human organism, increasing the sense of hunger, affecting carbohydrate and lipid metabolism, and controlling systemic energy balance mechanisms. Moreover, they influence the endocrine system functions, acting via two types of receptors, CB1 and CB2. The aim of the present study was to examine the number, distribution and activity of ghrelin and somatostatin producing endocrine cells in the pancreas of rats after a single administration of selective CP 55,940 agonist of CB1 receptor. The study was performed on 20 rats. Neuroendocrine cells were identified by immunohistochemical reactions, involving specific antibodies against ghrelin and somatostatin. The distribution and number of ghrelin- and somatostatin-immunoreactive cells were separately studied in five pancreas islets of each section. A performed analysis showed a decreased number of somatostatin-immunoreactive cells and a weak immunoreactivity of ghrelin and somatostatin containing neuroendocrine cells in the pancreatic islets of experimental rats, compared to control animals. The obtained results suggest that a single administration of a selective CP 55,940 agonist of CB1 receptor influences the immunoreactivity of endocrine cells with ghrelin and somatostatin expression in the pancreas islets

Estimation of gastric ghrelin-positive cells activity in hyperthyroid rats.

Ghrelin is a peptide of 28 amino acids that transmits appetite related signals from peripheral organs to the brain. The main source of ghrelin is stomach. The regulation of ghrelin secretion is still unknown. The finding that fasting and food intake, respectively increase and decrease the secretion of ghrelin suggests that this hormone may be a bridge connecting somatic growth with energy metabolism and appears to play an important role in the alteration of energy homeostasis and body weight in pathophisiological conditions. The purpose of this study was the evaluation of gastric ghrelin immunoreactivity and ghrelin plasma concentration in male Wistar rats with hyperthyroidism. Experimental model of hyperthyroidism was induced by intraperitoneal injection of levothyroxine at the dose of 80 microg/kg daily over 21 days. At the end of experiment the animals were anaesthetized, blood was taken from abdominal aorta to determinate plasma ghrelin concentration by RIA and then the animals underwent resection of distal part of stomach. Immunohistochemical study were performed using monoclonal specific antybodies against ghrelin. Hyperthyroidism was a reason of increase of gastric mucosal ghrelin - immunoreactivity, accompanied by a significant decreased of ghrelin plasma concentration. Those observations may indicate, that chronic administration of L-thyroxine cause the change of ghrelin plasma concentration in rats, probably via direct influence on gastric X/A-like cells, but this effect is not responsible for hyperphagia associated with hyperthyroidism

Cannabinoids enhance gastric X/A-like cells activity.

It has been reported that cannabinoids may cause overeating in humans and in laboratory animals. Although, endogenous cannabinoids and their receptors (CB1) have been found in the hypothalamus, and recently also in gastrointestinal tract, the precise mechanism of appetite control by cannabinoids remains unknown. Recently, ghrelin--a hormone secreted mainly from the stomach X/A-like cells was proposed to be an appetite stimulating agent. The aim of this study was the evaluation of the influence of a single ip injection of a stable analogue of endogenous cannabinoid--anandamide, R-(+)-methanandamide (2.5 mg/kg) and CP 55,940 (0.25 mg/kg), an exogenous agonist of CB1 receptors, on ghrelin plasma concentration and on ghrelin immunoreactivity in the gastric mucosa of male Wistar rats. Four hours after a single injection of both cannabinoids or vehicle, the animals were anaesthetized and blood was taken from the abdominal aorta to determinate plasma ghrelin concentration by RIA. Subsequently, the animals underwent resection of distal part of stomach. Immunohistochemical study of gastric mucosa, using the EnVision method and specific monoclonal antibodies against ghrelin was performed. The intensity of ghrelin immunoreactivity in X/A-like cells was analyzed using Olympus Cell D image analysis system. The attenuation of ghrelin-immunoreactivity of gastric mucosa, after a single injection of R-(+)-methanandamide and CP 55,940 was accompanied by a significant increase of ghrelin plasma concentration. These results indicate that stimulation of appetite exerted by cannabinoids may be connected with an increase of ghrelin secretion from gastric X/A-like cells

Activity of the thyroid parafollicular (C) cells in simple and hyperactive nodular goitre treated surgically - preliminary investigations

The aim of this study was to evaluate the significance of measuring calcitonin (CT) plasma concentrations in patients with simple and hyperthyroid goitre treated surgically. Eighty four patients who underwent operations during the years 2000-2002 were analysed. Plasma concentrations of CT were determined by commercially available radioimmunoassay on the day of hospitalisation. Elevated concentrations of CT were found in 8 patients: in 5 out of 26 (19.2%) and in 3 out of 33 (9.0%) patients with Graves’ disease and with multinodular goitre, respectively. No major differences in concentrations of CT were observed in patients with simple goitre. Postoperative morphological analysis of pathologically changed hyperactive thyroids showed the presence of enlarged C cells distributed either in small groups or even singly with weakening immunohistochemical reaction for CT. These observations may point to the possibility of a relationship between the functional state of the thyroid gland and the activity of C cells

Alteration of parafollicular (C) cells activity in the experimental model of hypothyroidism in rats.

Our previous study has shown the alteration of C cells activity in rats with experimental model of hyperthyroidism. The aim of the present study was the evaluation of parafollicular cells activity in rats with hypothyroidism evoked by propylthiouracil (PTU) given in drinking water over 21 days. Histological, ultrastructural and immunocytochemical studies using specific antibodies against calcitonin and CGRP were performed on thyroid glands taken from experimental and control groups of rats. Moreover, in all animals the calcitonin plasma levels were evaluated by radioimmunoassay. After chronic administration of PTU, thyroid image showed predominant microfollicular hyperplasia and attenuated density of parafollicular cells. The intensity of immunocytochemical reactions for CT and CGRP were weaker in the majority of C cells in comparison to the control rats, in which strong immunocytochemical reaction was observed. Examination in the electron microscope reveals the features of hypoactivity both in follicular and parafollicular cells, in which the quantity and electron density of secretory granules were smaller in comparison to the control group. These microscopic changes were accompanied by a significant decrease of calcitonin plasma concentration. Alteration of C cells activity in the experimental model of hypothyroidism, accompanied by microfollicular hypertrophy, may point to the mutual cooperation between parafollicular and follicular cells

Preliminary immunohistochemical investigations of thyroid C cells in an experimental model of hyperthyroidism

The role of the parafollicular (C) cells, the second most important cells in the thyroid gland, has not hitherto been clarified. They are considered to be disperse neuroendocrine cells of the APUD system and synthesise and release many of the regulatory peptides. Few publications are concerned with the evaluation of the structure and function of C cells in the thyroid gland or the probable relationship between these cells and the follicular cells in physiological and pathological conditions. For this reason immunohistochemical investigations were carried out into the activity of the C cells in rats in an experimental model of hyperthyroidism caused by chronic thyroxine influence. This C-cell activity was then evaluated. Differences in the quantity, distribution and calcitonin immunoreactivity of C cells were observed in hyperthyroid rats in comparison to the control group, together with a significant diminution of plasma TSH and calcitonin levels. Our preliminary study may indicate a functional interaction between follicular and parafollicular cells in the thyroid gland

Role of interleukin-6 on RANKL-RANK/osteoprotegerin system in hypothyroid ovariectomized mice.

Postmenopausal women frequently develop hypothyroidism. Estrogen depletion is accompanied by an increase of IL-6, accelerating bone turnover. The influence of hypothyroidism on bone metabolism in postmenopausal women is poorly understood. The aim of the study was an attempt to clarify the role of interleukin-6 on RANKL-RANK/osteoprotegerin system in hypothyroid ovariectomized mice. The study was performed on 56, 12-13 weeks old, female mice: C57BL/6J (wild-type; WT) and C57BL/6JIL6-/-Kopf (IL-6 knock-out; IL6KO). The mice were randomly divided into 8 groups with 7 mice in each one: 1/ WT controls, 2/ IL6KO controls, 3/ WT hypothyroid mice, 4/ IL6KO hypothyroid mice, 5/ WT ovariectomized, 6/ IL6KO ovariectomized, 7/ WT ovariectomized hypothyroid mice and 8/ IL6KO ovariectomized hypothyroid mice. Experimental model of menopause was produced by bilateral ovariectomy carried out in 8-9 weeks old mice. Experimental model of hypothyroidism was induced by propylthiouracyl administration in driking water. The serum levels of TRACP 5b, osteocalcin, OPG and RANKL were determined by ELISA. Serum RANKL concentrations were elevated significantly in all groups of ovariectomized mice as compared to respective controls, but in a minor degree in IL6KO hypothyroid mice as compared to wild-type animals. Moreover sRANKL values were significantly lower in IL6KO as compared to WT controls and IL6KO PTU injected mice. Osteoprotegerin serum levels were decreased in all IL-6 deficient mice and in a highest degree in sham-operated hypothyroid mice. To sum up, the results of the present study suggest that estrogens deficit is a strong stimulus for RANKL-RANK/OPG pathway that breaks an inhibitory influence of hypothyroidism even in IL-6 deficient mice

An immunohistochemical study of the thyroid parafollicular (C) cells in rats treated with cannabinoids - preliminary investigations

The purpose of the present study was to evaluate the effect of a single intraperitoneal injection of a stable analogue of endogenous cannabinoid anandamide - R-(+)-methanandamide (2.5 mg/kg) and CP 55,940 (0.25 mg/kg), an egzogenous CB1 receptor-agonist, on the calcitonin (CT) immunoreactivity of the thyroid parafollicular (C) cells. Four hours after injection with both cannabinoids CT immunoreactivity, evaluated with an avidin-biotin peroxidase complex method by means of rabbit antibodies against CT, was seen to be enhanced in the parafollicular cells in comparison to those of the control group. In thyroids taken from cannabinoid-treated rats the majority of follicles, particularly those located peripherally were large in size, and had low epithelium. Moreover, dilatation of the blood vessels was observed. These changes were accompanied by a significant decrease in CT plasma level, without changes in calcium concentrations. This is the first evidence that a single injection of the cannabinoids R-(+)-methanandamide and CP 55,940 significantly decreases the activity of thyroid C cells

Interleukin-6 is not essential for bone turnover in hypothyroid mice.

Interleukin-6 (IL-6) has been shown to be involved in the pathogenesis of several bone diseases characterized by an imbalance between bone resorption and formation. The aim of the study was to estimate serum markers of bone turnover: osteoclast-derived tartrate-resistant acid phosphatase form 5a (TRACP 5b) and osteocalcin in IL-6-deficient mice to assess the role of IL-6 in bone metabolism in hypothyroidism in mice. C57BL/6J (wild-type; WT) and C57BL/6J(IL6-/-Kopf) (IL-6 knock-out; IL6KO) mice randomly divided into 4 groups with 10 in each one: 1/ WT mice in hypothyroidism (WT-ht), 2/ WT controls, 3/ IL6KO mice with hypothyroidism (IL6KO-ht) and 4/ IL6KO controls. Experimental model of hypothyroidism was induced by intraperitoneal injection of propylthiouracyl. The serum levels of TRACP 5b and osteocalcin were determined by ELISA. Serum concentrations of TRACP 5b (median and interquartile ranges) were significantly decreased in both groups of mice with hypothyroidism: WT (3.2 (2.5-4.7) U/l) and IL6KO (2.6 (1.8-3.5) U/l) as compared to the respective controls. Similarly, serum osteocalcin levels were significantly reduced in both groups of mice in experimental hypothyroidism: WT (25.8 (23.0-28.2) ng/ml) and IL6KO (21.5(19.0-24.6) ng/ml) in comparison to the respective controls. There were no significant differences in bone turnover markers between IL6KO and WT mice both in hypothyroid and control animals. The results of the present study suggest that IL-6 does not play an important role in bone turnover in both euthyroid and hypothyroid mice

CCN1 expression in interleukin-6 deficient mouse kidney in experimental model of heart failure

Chronic heart failure often leads to worsening of the renal function. Mediators of this process include inflammatory and neuroendocrine factors. CCN1 (Cyr 61), a member of growth factor-inducible immediate early genes, which modulates inflammation and fibrogenesis, is excreted with urine in the early phase of acute renal injury and may be involved in the pathogenesis of the cardiorenal syndrome. The aim of the study was to evaluate CCN1 protein abundance and localization in the kidney of IL-6-deficient C57BL/6J (IL-6 KO) mice and respective wild-type (WT) animals in basal conditions and in animals with chronic heart failure twelve weeks after myocardial infarction. Age- and sex-matched mice from both strains subjected to sham operation served as controls. One group of WT animals subjected to myocardial infarction was treated with antagonist of AT1 receptor telmisartan over 12 weeks. Abundance and localization of CCN1 protein in kidney were assessed with Western blotting and immunohistochemistry, respectively. In all groups the strongest immunohistochemical reaction for CCN1 was observed in distal convoluted tubules and in smaller arteries, however, the total expression of CCN1 protein was lower in IL-6 KO mice in comparison to WT animals. The main difference in CCN1 distribution between the examined genotypes was lack of reaction in internal renal medulla and very weak reaction in proximal convoluted tubules in IL-6 KO mice. Experimental heart failure only slightly attenuated the expression of CCN1 protein in the kidney of WT mice and had no effect in IL-6 KO mice. Although, blockade of AT1 receptor did not alter CCN1 protein expression in kidneys of WT mice after myocardial infarction, it significantly changed its CCN1 distribution in the renal tubular system. (Folia Histochemica et Cytobiologica 2013, Vol. 51, No. 1, 84–91