Histochemical and immunohistochemical localization of nitrergic structures in the carotid body of spontaneously hypertensive rats

• Published in: Acta histochemica Vol. 122; no. 2; p. 151500
• Main Authors: Atanasova, Dimitrinka Y., Dandov, Angel D., Dimitrov, Nikolay D., Lazarov, Nikolai E.
• Format: Journal Article
• Language: English
• Published: Germany Elsevier GmbH 01-02-2020
• Subjects: Carotid body; Hypertension; NADPH-d histochemistry; NOS immunohistochemistry; Spontaneously hypertensive rats; Hypertension; NADPH-d histochemistry; Spontaneously hypertensive rats; NOS immunohistochemistry; Carotid body
• DOI: 10.1016/j.acthis.2019.151500
• EISSN: 1618-0372
• ISSN: 0065-1281

•Glomus and sustentacular cells in the CB of SHRs are devoid of nNOS and eNOS immunoreactivity.•Glomus cells and blood vessels in the hypertensive CB exhibit moderate iNOS immunoreactivity.•In the hypertensive CB the protein expression of nNOS and eNOS is significantly down-regulated.•The levels of iNOS in the rat glomic tissue are up-regulated in the hypertensive state.•Impaired NO synthesis contributes to hypertension via an increase in sympathetic nerve activity.
The carotid body (CB) is a multipurpose metabolic sensor that acts to initiate cardiorespiratory reflex adjustments to maintain homeostasis of blood-borne chemicals. Emerging evidence suggests that nitric oxide increases the CB chemosensory activity and this enhanced peripheral chemoreflex sensitivity contributes to sympathoexcitation and consequent pathology. The aim of this study was to examine by means of NADPH-diaphorase histochemistry and nitric oxide synthase (NOS) immunohistochemistry the presence and distribution of nitrergic structures in the CB of spontaneously hypertensive rats (SHRs) and to compare their expression patterns to that of age-matched normotensive Wistar rats (NWRs). Histochemistry revealed that the chemosensory glomus cells were NADPH-d-negative but were encircled by fine positive varicosities, which were also dispersed in the stroma around the glomeruli. The NADPH-d-reactive fibers showed the same distributional pattern in the CB of SHRs, however their staining activity was weaker when compared with NWRs. Thin periglomerular, intraglomerular and perivascular varicose fibers, but not glomus or sustentacular cells in the hypertensive CB, constitutively expressed two isoforms of NOS, nNOS and eNOS. In addition, clusters of glomus cells and blood vessels in the CB of SHRs exhibited moderate immunoreactivity for the third known NOS isoenzyme, iNOS. The present study demonstrates that in the hypertensive CB nNOS and eNOS protein expression shows statistically significant down-regulation whereas iNOS expression is up-regulated in the glomic tissue compared to normotensive controls. Our results suggest that impaired NO synthesis could contribute to elevated blood pressure in rats via an increase in chemoexcitation and sympathetic nerve activity in the CB.