Abstract. Atrial natriuretic peptide (ANP) is a regulatory hormone widely expressed, along with its receptors, in organs and body tissues. ANP is well known to inhibit aldosterone secretion from mammalian adrenals, but its effect on glucocorticoid-hormone production is controversial. In vivo experiments showed that prolonged ANP administration raised the plasma concentration of cortisol in both normal and dexamethasone/captopril-treated guinea pigs (i.e. in animals with pharmacologically interrupted hypothalamic-pituitaryadrenal axis and renin-angiotensin system). ANP did not affect cortisol secretion from dispersed guinea pig zona fasciculatareticularis cells, but enhanced catecholamine release from adrenomedullary cells. ANP stimulated cortisol output from guinea pig adrenal slices containing medullary chromaffin tissue, and the ß-adrenoceptor antagonist l-alprenolol blocked this effect. The conclusion is drawn that ANP, when the structural integrity of the adrenal gland is preserved, is able to enhance glucocorticoid secretion in guinea pigs, through an indirect mechanism involving the rise in the catecholamine release, which in turn, acting in a paracrine manner, stimulate secretion of inner adrenocortical cells. IntroductionAtrial natriuretic (ANP) is the first member of a family of peptides originally discovered in the late 1970s in the secretory granules of atrial myocytes, and including brain natriuretic peptide and C-type natriuretic peptide (reviewed in ref. 1). ANP acts via two G protein-coupled receptors, named A and B, that are coupled to guanylate cyclase (reviewed in refs. 2,3). Subsequent studies showed that ANP and its receptors are present in several extra-atrial tissues, among which are heart ventricles, blood vessels, brain, lungs, kidneys and endocrine glands.Mammalian adrenal zona glomerulosa possesses A and B subtypes of ANP receptors, and many lines of evidence indicate that ANP, via the cyclic-GMP pathway, inhibits either basal or agonist-stimulated aldosterone secretion (reviewed in refs. 4,5). The possible effects of ANP on the zona fasciculata and glucocorticoid secretion have been far less investigated. Although ANF receptors have been demonstrated in the rat zona fasciculata (6), most studies did not report any effect of ANP on glucocorticoid secretion in this species (1,4). However, findings suggest that ANP is able to lower basal and especially ACTH-stimulated glucocorticoid production from cultured human and cow zona fasciculata cells (7,11). The A subtype of ANP receptors is expressed also in the adrenal medulla (12,13), and the bulk of evidence indicates that ANP inhibits catecholamine release (14-17). However, ANP has been more recently reported to induce tyrosine hydroxylase mRNA expression and to raise catecholamine content in rat pheochromocytoma PC12 cells, via the guanylate cyclase-dependent cascade (18).Therefore, it seemed worthwhile to investigate the in vivo and in vitro effects of ANP on glucocorticoid and catecholamine secretion from the guinea-pig adrenal gland. Gu...

The ultrastructure of the corpuscles of Stannius (CS) of Heteropneustes fossilis reveals a homogenous cellular composition characterized by only one cell type, with large secretory granules and abundant ribosomal endoplasmic reticulum. These cells are comparable to the type 1 cell described in the CS of other teleosts; type 2 cells, whose presence is ubiquitous in the CS of freshwater species are absent in H. fossilis. Our data on the CS of H. fossilis demonstrate that not all freshwater species possess type 2 cells in their CS and these are not essential for life in freshwater

Insulin-like growth factor (IGF)-I is a ubiquitously synthesized peptide that, along with IGF-II, acts via the IGF-R type I receptor. IGF-I and its receptor are expressed in the adrenal gland of humans and bovines, the secretion of which they seem to stimulate. As in humans and cows, the main glucocorticoid hormone secreted by guinea-pig adrenals is cortisol, and hence we have studied the adrenocortical effects of IGF-I in this species. In vivo experiments showed that prolonged IGF-I administration raised the plasma concentration of cortisol in both normal and dexamethasone/captopriltreated guinea pigs, thereby ruling out the possibility that IGF-I may act by activating the hypothalamic-pituitaryadrenal axis and the renin-angiotensin system. In vitro experiments demonstrated that IGF-I enhanced basal, but not maximally agonist [ACTH and angiotensin-II (Ang-II)]stimulated, cortisol secretion from freshly dispersed guinea-pig inner adrenocortical cells. The IGF-I immuno-neutralization suppressed the IGF-I secretagogue effect, without altering the cortisol response to both ACTH and Ang-II. IGF-I raised cyclic-AMP and inositol triphosphate release from dispersed guinea-pig cells, and the effect was reversed by the adenylate cyclase inhibitor SQ-22536 and the phospholipase-C (PLC)

We have investigated the effect of the prolonged administration of melatonin on the plasma concentration of glucocorticoids in rats and palm squirrels, whose hypothalamo-pituitaryadrenal axis and renin-angiotensin system were suppressed by the simultaneous administration of dexamethasone and captopril. Dexamethasone and captopril administration for two weeks markedly lowered the blood level of corticosterone in rats and cortisol in palm squirrels. The injection of melatonin during the second week of treatment caused a further significant lowering in the glucocorticoid plasma concentration. These findings suggest that melatonin exerts a sizeable glucocorticoid antisecretagogue effect in rats and squirrels, acting directly on the adrenal glands.Melatonin is a multifunctional hormone, mainly secreted by the pineal gland, the effects of which on the hypothalamo-pituitary-adrenal (HPA) axis are well established (14). To summarize, melatonin is reported to be a potent inhibitor of the central branch of the HPA axis (16), as well as to reset dysregulation of this axis, at least in the rat (7). However, there is a marked disagreement as far as the direct effect of this hormone on the secretory activity of adrenal cortex is concerned. In fact, both stimulating (2, 4, 13, 15) and inhibitory effects have been described (5, 9, 11, 17). All these study were carried out using dispersed or cultured adrenocortical cells, i.e. experimental models which do not reproduce in viva physiolog- ical conditions. It, therefore, seemed worthwhile to study the effect of the prolonged melatonin administration on the blood concentrations of glucocorticoid in rats and palm squirrels, whose HPA axis and renin-angiotensin system (RAS) were pharmacologically interrupted.Adult Sprague-Dawley male rats (ZOO--250g body weight, obtained from Charles-River; Como, Italy), and palm squirrels (Fzmambzzlus pennanri, Wrougton) (300-350g body weight, obtained from the breeding facilities of our Zoology Department) were housed two per cage, kept under a 12:12 h light-dark cycle, and maintained on a standard diet and tap water ad Zibitrzzm. After being adapted to the laboratory conditions for 15 days, the animals were divided into three equal groups (rats: 11:10; palm squirrels: 11:50), which were treated as follows: 1) dexamethasone (2.5 mg/kg; Sigma Chemical Company, St. Louis, MO, U.S.A.) and captopril (8.3 mg/kg; Squibb, Rome, Italy) for 14 days; they were subcutaneously injected twice a day, at 1 a.m. and 1 p.m. to counteract circadian rhythm of glucocorticoids secretion which depends on both HPA axis and

Tomato is the second most important vegetable crop consumed globally, by the virtue of its antioxidant-rich phytochemicals and bioactive compounds. Identifying genotypes with high antioxidant capacities and nutritionally rich phytochemicals is imperative for improving human health. The present study aimed to analyze 21 antioxidant and nutritional compounds in 93 geographically diverse, high yielding, better quality, stress tolerant tomato genotypes (hybrids, parental lines, inbred lines, and advanced lines). Significant variation (p < 0.05) was detected for investigated traits among the tested genotypes. Principal component analysis revealed the hybrids NIAB-Jauhar, Iron-lady F1, NBH-258, Ahmar F1, NIAB-Gohar, the parents H-24, B-25, AVTO1080, Astra and AVTO1003, as well as the lines LBR-17, AVTO1315, AVTO1311 and Lyp-1 revealed superior performance for the traits such as chlorophylls, lycopene, total carotenoids, total antioxidant capacity, total oxidant status, protease, alpha-amylase and total flavonoid content. Whereas the hybrids Surkhail F1, NBH-204, NBH-229, NBH-151, NBH-196, NBH-152, NBH-261, NBH-228, NIAB-Jauhar, NBH-256 and NBH-255, the lines 21354, AVTO1315, Newcherry, LA4097, AVTO1311 and UAF-1 together with the parents Naqeeb, NCEBR-5, M-82 and LBR-10 exhibited significant contribution to the traits such as total soluble sugars, reducing sugars, malondialdehyde, ascorbic acid, esterase, peroxidase and superoxide dismutase. Moreover, the semi-determinate and determinate tomato genotypes together with the categories parent and line with positive factor scores of 3.184, 0.015, 0.325 and 0.186 in PC- I, exhibited better performance for the trait such as total chlorophylls, lycopene, total carotenoids, total oxidant status, protease, alpha-amylase, total antioxidant capacity, esterase and total flavonoid content. Whereas again the semi-determinate and indeterminate tomato genotypes along with the category hybrid with positive factor scores of 2.619, 0.252 and 0.114 in PC- II, exhibited better performance for the traits such as total soluble sugars, reducing sugars, chlorophyll b, malondialdehyde content, ascorbic acid, superoxide dismutase and peroxidase. Hybrid vigor was observed in the hybrids for investigated traits. The aforementioned tomato genotypes showing outstanding performance in the respective traits can be exploited in the breeding programs to improve nutritional quality of tomato that can further improve human health.