Expression analysis of the thyrotropin-releasing hormone receptor (TRHR) in the immune system using agonist anti-TRHR monoclonal antibodies

Monoclonal anti-rat thyrotropin-releasing hormone (TRH) receptor (TRHR)-specific antibodies (mAb) were generated by immunization with synthetic peptides of rat TRHR partial amino acid sequences; one (TRHR01) was directed against a sequence (84-98) in the extracellular portion of the rat TRHR reported to be constant among different species, including man, and the second (TRHR02) recognizes the C-terminal region sequence 399-412. In lysates from GH4C1 cells, a clonal rat pituitary cell line, both mAb recognize the TRHR in Western blot analysis, and TRHR02 immunoprecipitates the TRHR. Incubation of GH4C1 cells with the mAb causes a fluorescence shift in fluorescence-activated cell sorting analysis. The cells were stained specifically by both mAb using immunocytochemical techniques. Furthermore, TRHR01 is agonistic in its ability to trigger Ca2+ flux, and desensitizes the TRH receptor. We tested for TRHR in several rat organs and found expression in lymphoid tissues. TRHR01 recognizes the human TRHR, and analysis of human peripheral blood lymphocyte and tonsil-derived leukocyte populations showed receptor expression in non-activated and phytohemagglutinin-activated T and B cells.

Effect of aluminium on osteocalcin production in the rat

In renal failure, aluminium is an important factor in the development of osteomalacia. The mechanism by which aluminium produces osteomalacia is not clear; it may be toxic to the osteoblast, and as a result of its effect on osteoblasts, impair mineralisation. Another possibility is that aluminium may directly impair mineralisation independent of osteoblast function. Osteocalcin is considered to be a specific marker of osteoblast activity and its production is stimulated by calcitriol. In the present study, calcitriol-stimulated production of osteocalcin was studied as a marker of osteoblast activity in aluminium toxicity. Four groups of rats were evaluated: (1) normals; (2) normal renal function plus aluminium; (3) renal failure; and (4) renal failure plus aluminium. Osteocalcin production was determined by measuring serum osteocalcin at baseline and after stimulation with calcitriol. In rats receiving aluminium, the baseline serum osteocalcin levels were not different from their respective controls. After stimulation with calcitriol, the increase in serum osteocalcin was less in the renal failure group receiving aluminium. However, when corrected for the number of osteoblasts, the increase in serum osteocalcin was not decreased. In summary, although aluminium administration decreased the number of osteoblasts in rats with renal failure, osteocalcin production by the remaining osteoblasts was not decreased.

Development of liver fibrosis during aging: effects of caloric restriction

Liver is the central metabolic organ of the body and diet is considered one of the main environmental factors that can impact on aging liver. In the elderly stage liver function is relatively well conserved although there are a variety of not well defined morphological changes related to liver fibrosis which is commonly associated with an inflammatory state. The aim of this paper is to study these alterations during the physiological process of aging in Wistar rats and also test if caloric restriction (CR) could ameliorate them. As fibrosis is associated to hepatic stellate cell (HSC) function we also analyzed these cells during aging. Livers from five groups of male Wistar rats (3-, 8-, 24-months old ad libitum and 8- and 24-months caloric restricted rats) were used in this study. Histological analysis, expression of genes implicated in liver fibrosis and the status of inflammatory step-pathways as p38 mitogen-activated protein kinase (p38-MAPK), c-Jun N-terminal kinase (JNK) and the nuclear factor kappa B (NFkB) isoforms, p50 and p65, in cytosolic and nuclear fractions were performed. During elderly, associated with morphological change of HSC, there is a progressive increase in collagen deposition due to an inhibition in collagen degradation. Higher expression of cytokines and the activation of inflammatory pathways are associated with aging. CR ameliorates these circumstances being more effective when it started in middle age. In conclusion elderly stage is associated to a mild fibrotic and inflammatory state in the liver which could be ameliorated after CR.