Nitric Oxide and Calcium Binding Protein in Hypoxic Rat Carotid Body

Abstract

The occurence and distribution of nitric oxide synthase (NOS)-containing nerve fibers have been demonstrated by means of NOS immunohistochemistry and NADPH-diaphorase (NADPH-d) histochemistry (Wang, et al., 1993; Grimes, et al., 1994; Hôhler, et al., 1994; Tanaka, et al., 1994). Recently, we reported the distribution of NOS immunoreactive fibers in the chronically hypoxic rat carotid body (Kusakabe, et al., 1998). The density of NOS fibers in the chronically hypoxic carotid body was significantly reduced. This finding suggests that altered nitrergic innervation of the chronically hypoxic carotid body is a feature of hypoxic adaptation. On the other hand, the first evidence for the presence of the calcium binding protein (spot 35-protein) in afferent nerve fibers in the rat carotid body has been shown by Kondo (1990). Recently, in the same hypoxic carotid body, we reported a similar reduction in the density per unit area of calbindin D-28k immunoreactive nerve fibers (Kusakabe et al., 2000). Calbindin D-28k belongs to a family of calcium binding proteins, and plays important roles in the storage and transport of intracellular Ca²⁺ (Baimbridge and Miller, 1982).