Carotid body chemoreceptors in dissociated cell culture

Abstract

Carotid body (CB) glomus or type 1 cells act as peripheral chemoreceptors which detect changes in arterial PO(2), PCO(2), and pH and help maintain homeostasis via the reflex control of ventilation. Over the last approximately 12 years significant progress has been made towards understanding chemotransduction mechanisms using freshly isolated or cultured type 1 cells. The latter preparation allows several powerful experimental manipulations (e.g., co-culture with sensory neurons) resulting in significant advances in our understanding of CB chemoreception. Here, we review several properties of type 1 cells after several days to weeks in culture. Typically, cultured type 1 cells grow in monolayer clusters enveloped by glial-like, type II, or sustentacular cells, which are immunopositive for the glial marker, glial fibrillary acid protein (GFAP). These cells can undergo DNA synthesis, evidenced by uptake of bromodeoxyuridine (BrdU), and show a limited capacity for cell division. Mitosis and survival of type 1 cells can be regulated by oxygen tension and/or growth factors (e.g., bFGF, insulin). In the rat, type 1 cells are immunopositive for several monoaminergic markers, including tyrosine hydroxylase (TH), dopamine transporter (DAT), and 5-HT. They also express cholinergic markers (e.g., vesicular acetylcholine transporter; VAChT), the highly conserved synaptic vesicle protein (SV2), and gap junctional proteins including Connexin 32 (Cx32). Moreover, in long-term culture ( approximately 2 weeks) they retain expression of O(2)-sensitive, TASK-1-like, and Ca(2+)-dependent (BK), K(+) channels as revealed by immunocytochemistry or RT-PCR analysis of mRNA extracted from type 1 clusters after removal from the culture surface.

H 2 S mediates O 2 sensing in the carotid body

“…CSE immunoreactivity was seen in glomus cells of carotid bodies from CSE +/+ mice as evidenced by colocalization with tyrosine hydroxylase (TH), an established marker of glomus cells (11,12). CSE expression was absent in carotid bodies from CSE −/− mice (Fig.…”

“…3 and 11. For assessing CSE immunoreactivity, sections (8 μm thick) were incubated at room temperature for 2 h with polyclonal rabbit anti-CSE antibody (1:400), this antibody was raised using bacterially purified full-length His-tagged CSE as antigen, and monoclonal mouse anti-tyrosine hydroxylase (1:2,000; Sigma), an established marker of glomus and chromaffin cells (11,12), followed by Texas red-conjugated goat anti-rabbit IgG and FITC-conjugated goat anti-mouse IgG (1:250; Molecular Probes) in PBS with 1% normal goat serum and 0.2% Triton X-100. After washing with PBS, sections were mounted in DAPI-containing media and visualized using a fluorescent microscope (Eclipse E600; Nikon).…”

Inherent variations in CO-H 2 S-mediated carotid body O 2 sensing mediate hypertension and pulmonary edema

“…To determine whether variations in the number of glomus cells, the primary O 2 sensing cells, account for the differences in carotid body O 2 sensing, carotid body sections were stained for tyrosine hydroxylase, a marker of glomus cells (18) (Fig. 1C).…”

Endogenous H2S is required for hypoxic sensing by carotid body glomus cells

“…The carotid body is primarily composed of two cell types: 1) glomus cells or type I cells, which are of a neuronal phenotype; and 2) sustentacular or type II cells, which resemble glial cells of the nervous system (9,10,12,19). Type I cells express a variety of neurotransmitters and are in synaptic contact with the afferent nerve endings of the sinus nerve (6,14,16,18).…”