title: Histochemical demonstration of tripeptidyl aminopeptidase I in the rat carotid body.
abstract: Tripeptidyl aminopeptidase I (TPP I) is a lysosomal exopeptidase that is widely distributed throughout the central nervous system (CNS) and internal organs in many mammalian species. The enzyme is involved in the breakdown of collagen and different peptides. The carotid body (CB) is the main peripheral arterial chemoreceptor playing an important role in the control of breathing and the autonomic control of cardiovascular function. In response to hypoxia its neuron-like glomus cells release a variety of peptide transmitters that trigger an action potential through the afferent fibers, thus conveying the chemosensory information to the CNS. In the present study we investigated the histochemical localization of TPP I in the CB of rats. Enzyme histochemistry showed high activity of TPP I in CB glomeruli. In particular, the glomus cells contained many TPP I-positive granules, while the glial-like sustentacular cells displayed a slightly fainter reaction. The interglomerular connective tissue was also weakly stained. The results show that both the parenchymal cells of the rat CB express, albeit with different intensity, TPP I. Taken together with our previous enzyme histochemical investigations on the rat CB, it seems likely that the glomus cells possess enzymatic equipment necessary for the neuropeptide intracellular and collagen extracellular initial degradation. These findings also suggest that TPP I is involved in the general turnover of chemotransmitters between glomus cells and sensory nerve endings which emphasizes its importance for chemoreception under hypoxic conditions.
authors: Institute of Neurobiology, Bulgarian Academy of Sciences, Sofia, Bulgaria; Institute of Experimental Morphology, Pathology and Anthropology with Museum, Bulgarian Academy of Sciences, Sofia, Bulgaria.
authors: Dimitrinka
authors: D
authors: Atanasova
authors: Institute of Neurobiology, Bulgarian Academy of Sciences, Sofia, Bulgaria; Department of Anatomy and Histology, Medical University of Sofia, Sofia, Bulgaria. Electronic address: nlazarov@medfac.acad.bg.
authors: Nikolai
authors: N
authors: Lazarov
mesh_terms: D000626:Aminopeptidases / Q000378:metabolism*; D000818:Animals; D002344:Carotid Body / Q000166:cytology / Q000378:metabolism*; D015687:Cell Hypoxia; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases / Q000378:metabolism*; D005260:Female; D007150:Immunohistochemistry; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D057057:Serine Proteases / Q000378:metabolism*; D000091346:Tripeptidyl-Peptidase 1
chemical_list: D009419:Nerve Tissue Proteins; C000717269:Tpp1 protein, rat; D000091346:Tripeptidyl-Peptidase 1; D057057:Serine Proteases; D000626:Aminopeptidases; D004152:Dipeptidyl-Peptidases and Tripeptidyl-Peptidases
keywords: Carotid body; Enzyme histochemistry; Glomus cells; Rat; Sustentacular cells; Tripeptidyl peptidase I