As DPP IV is occasionally expressed in thyrocytes of benign thyroid disorders [18] a link to proliferation has been suggested [11]. Increased APN expression is correlated with progression and metastasis in colorectal, pancreatic carcinoma and undifferentiated thyroid carcinoma [12, 19, 20]. Dipeptidyl peptidase II (DPP II, EC 3.4.14.2), a lysosomal protease ubiquitously expressed in many cells including normal thyrocytes of mammalian origin [21], is thought to play check details a role in the release of hormone from thyroglobulin [22]. Dipeptidyl peptidase IV (DPP IV, CD26, EC 3.4.14.5)

is a trans-membrane type II glycoprotein with multifaceted function. As well as the integral membrane form, a soluble form is found in serum and semen. In contrast to thyroid follicle cells, Pevonedistat supplier most other types of human cell express DPP IV [23]. DPP IV is most up-regulated in papillary thyroid carcinoma [24, 25] and apparently induced by RET/PTC mutations [26]. Aminopeptidase N (APN, aminopeptidase M, alanine aminopeptidase, CD13, EC 3.4.11.2), is expressed in anaplastic thyroid carcinoma cells but not in normal thyrocytes [12]. In porcine thyrocytes, by contrast, APN is a marker of the apical thyrocyte membrane [27, 28]. To identify species with an identical pattern of protease activity compared to human thyrocytes, here we localized protease activities using synthetic substrates. The activities of DPP II, DPP IV and APN were

studied in animal species used for investigating thyroid function, namely human, porcine,

rat, mouse, bovine and ovine thyrocytes. Methods Tissue samples Cadavers of rats (female, Sprague–Dawley) and mice (female, Balb/c), which had been used for other experiments, were see more obtained from the Institute of Pharmacology and the Institute of Anatomy, respectively. Porcine, bovine and MG-132 ovine thyroid glands were obtained from the local slaughterhouse. Samples from human thyroid tissue were obtained from the surgical department of the University after informed consent of the patients. Animal procedures were performed according to the guidelines of the local authorities. All experiments on human subjects were conducted in accordance with the Helsinki Declaration of 1975. For the localization of DPP IV and APN activities unfixed tissues were used. For the demonstration of DPP II 0.5 cm3 cubes of thyroid tissue were fixed in neutral buffered 4% formaldehyde solution with 30% sucrose for 24h at RT. After fixation, samples were rinsed for 24h at RT in distilled water containing 30% sucrose and 1% gum arabicum. Tissue samples were embedded in Tissue Tec (Miles) and deep-frozen in isopentane per-cooled with liquid nitrogen. Detection of protease activity Protease activity in tissues and in cells was detected by cleavage of specific synthetic substrates. The synthetic substrate is bound to a tag, which together with the coupler yields a colored product, when released from the substrate.