Endocrine Abstracts

The activity of the hypothalamo–pituitary–adrenal axis (HPA) is under control of endocrine, nervous and immune systems, in which opioids and recently discovered ghrelin play important role. Mannan polysaccharide is often used as an alternatives to antibiotics, however, its role in the stimulation of the immune system is still uncertain. As a part of study dealing with the interaction of different factors during the growth and development the experiment was carried out in order to estimate the effect of prolonged treatment of mannan on the HPA synthesis of proghrelin and proenkephalin. Animal study were performed on the 30-days-old female lambs fed with standard food or with addition of prebiotic – mannan polysaccharide, isolated from the cell wall of Saccharomyces cerevisiae. During 30 days of experiment lambs were i.v. injected with saline (control) or naltrexone (3 mg/kg b.w.) five times every 7 days. Fragments of hypothalami, pituitaries and adrenals were taken out, frozen and directed to measurement of the expression of mRNAs for proghrelin and proenkephalin by the in situ hybridization method. Prolonged treatment with mannan significantly affected the expression of mRNAs for proghrelin and proenkephalin in the hypothalamus and pituitary. Unexpectedly, naltrexone, an opioid receptor antagonist, decreased the expression of mRNA coding for proenkephalin and increased for proghrelin in mannan fed animals.

In contrast, the response of both mRNAs in adrenals to polysaccharide treatment was very weak. Thus, the obtained results showed the interaction of hypothalamo–pituitary–adrenal opioids and ghrelin in the response to activated immune system.