Nasal turbinates

FIGURE 5.15 Cross-section of human nasal turbinates at various positions along the airway. Distances indicated are from the nares. The medial surface in each cross-section represents the nasal septum. (Modified from Guilmette et al. )... 

Nasal vasculature may offer some insight into this question, though research to date has been equivocal. Nasal turbinate vessels can be classified as either capacitance vessels or resistive vessels. Capacitance vessels appear to vasodilate in response to infection while resistance vessels appear to respond to cold stimuli by vasoconstriction. Buccal vascular structures also respond to thermal stimuli but appear to respond principally to cutaneous stimuli. How pharyngeal and tracheobronchial submucosal vessels react to thermal stimuli is not known, though cold-induced asthma is believed to result from broncho-spasms caused by susceptible bronchial smooth muscle responding to exposure to cold dry air.- This asthmatic response suggests an inadequate vascular response to surface cooling. 

Concha One of three bony projections in the nasal turbinate region. 

Nasal turbinates Region within the nasal cavity denoted by convoluted... 

Decongestants such as OTC pseudoephedrine are sympathomimetic agents that constrict capacitance vessels in the nasal turbinates.17 Decongestants effectively reduce nasal congestion and to some extent rhinorrhea associated with AR.8,12 The recommended dose of pseudoephedrine is 30 to 60 mg every 4 to 6 hours for a maximum daily dose of 240 mg.15 Systemic adverse effects such as irritability, dizziness, headache, tremor, tachycardia, and insomnia can occur. Additionally, use is associated with increased blood pressure and intraocular pressure and urinary obstruction.8,12... 

Excess mucus in the nasal turbinates, irritation of the epithelium, and increased incidence of a mycoplasma respiratory infection were seen in rats with inhalation exposure to 260 ppm for 6 weeks and in pregnant rats with inhalation exposure to 48 ppm for 11 days. Pulmonary irritation was also present in pregnant rats treated with an oral dose of 500 mg/kg/day for 11 days (Weeks et al. 1979). Effects on the respiratory epithelium were not apparent in the tissue of the lungs, nasal cavity, nasal turbinates, larynx, trachea, or bronchi based on histopathological examination (NTP 1977, 1989 Weeks et al. 1979). Exposure to... 

V. E. Steele and J. T. Arnold. Isolation and long-term culture of rat, rabbit and human nasal turbinate epithelial cells. In Vitro Cell Dev Biol 21 671-687 (1985). 

A study was conducted to examine proliferative nasal epithelial lesions in F344 rats following subchronic inhalation of 1,2-dibromoethane at concentrations of 0, 3, 10, or 40 ppm (Nitschke et al. 1981). The study incorporated serial sacrifices and sacrifices after an 88-89-day postexposure period. Rats in the mid - and high-dose groups had hyperplasia of nasal turbinate epithelium rats at the highest dose also exhibited nonkeratinizing squamous metaplasia of respiratory epithelium of the nasal turbinates. 

Respiratory effects after oral exposure to 1,4-dichlorobenzene in humans have not been reported. Rats exposed to 1,200 mg/kg/day 1,4-dichlorobenzene for 13 weeks exhibited necrosis of the nasal turbinates, yet no such effects were noted in mice exposed to similar oral concentrations (NTP 1987). 

High doses of dioxane by oral administration produced malignant tumors of the nasal cavity and liver in rats, and mmors of the liver and gallbladder in guinea pigs." Rats administered either 0.5% or 1.0% (vol/vol) in the drinking water had squamous cell carcinomas of the nasal turbinates hepatocellular adenomas were seen in the dosed females." In another study, inhalation of 111 ppm, 7 hours/day, 5 days/week for 2 years did not result in any increased tumor incidence in rats. ... 

No deaths were observed in rats at concentrations up to 800 ppm or in mice up to 400 ppm in an NTP study lasting 13 weeks (6 hours/day, 5 days/week). Nasal cavity lesions and reduced body weight were seen in rats exposed at 800 ppm. In mice, renal tubular necrosis was found at 800 ppm, a dose that was lethal. Inflammation of the nasal turbinates was observed in female mice at 100 ppm and above and in male mice at 2 00 ppm and above. In an earlier study, slight growth retardation was observed in rats and mice exposed at 600 ppm for 13 weeks inflammatory and degenerative changes in the nasal mucosa were observed in both species. Myeloid hyperplasia in bone marrow occurred in male rats only. No effects were noted at 75 or 150ppm. 

In inhalation studies, there was some evidence of carcinogenicity in rats exposed at 400 ppm, as indicated by an increased incidence of papillary adenomas of the nasal turbinates." In mice, there was clear evidence of carcinogenic-... 

Chronic 2-year studies showed a significant increase in the incidences of adenomas and carcinomas of the nasal cavity in high-dose rats fed diets containing 3000ppm of 2,6-xylidine. The carcinomas were highly invasive and frequently destroyed the nasal turbinates and nasal septum. Rhabdomyosarcomas, a rare tumor of the nasal cavity were also observed in the high-dose male and females. The nonneo-plastic lesions observed in the nasal cavity included acute inflammation, epithelial hyperplasia, and squamous metaplasia. In addition, subcutaneous fibromas and fibrosarcomas occurred in both males and females and there was an increased incidence of neoplastic nodules in the livers of female rats. 

Information regarding respiratory effects in orally-exposed animals is limited to a report of a significantly increased incidence of nasal lesions (goblet cell hyperplasia and inflammation of nasal turbinates) following 90 days of exposure to chlorine dioxide in the drinking water at concentrations that resulted in estimated doses as low as 2 mg/kg/day in males and 8 mg/kg/day in females (Daniel et al. 1990). These nasal effects were likely caused by inhalation of chlorine dioxide vapors released from the water rather than a systemic respiratory effect following oral exposirre. 

In intermediate- and chronic-duration studies with rats, histology of the lung, trachea, or nasal turbinate was not altered by FireMaster FF-1 or FireMaster BP-6 dosages of < 30 mg/kg/day by gavage for 30 days (Gupta et al. 1981), < 10 mg/kg/day in the diet for 30 days (Akoso et al. 1982a Sleight et al. 1978),... 

---