Evidence that taste buds are not present on the human adult uvula. (Original Article).

Abstract

We conducted a study to investigate whether taste buds are present on the human adult uvula. Our impetus was to determine whether surgical procedures that involve removal of the uvula can affect taste perception. Five human uvulae were removed via a modified carbon dioxide laser-assisted uvulopalatoplasty in an outpatient office setting. The uvulae were serially sectioned and stained with a solution specific for membrane-bound calcium-modulated adenosine triphosphatase, a high concentration of which is found in taste receptors. Examination of the stained sections under light microscopy failed to show that any taste receptors were present in any of the uvulae. This finding suggests that the taste disturbances noted after surgical procedures involving removal of the uvula are not attributable to a loss of taste receptors.

Introduction

The discussion of taste buds is usually limited to receptors on the tongue, but some authors have investigated the number and distribution of taste receptors on other human tissues. (1,2) Taste buds have been identified on the soft palate, pharynx, epiglottis, and larynx. Uncertainty exists as to the existence of taste buds on the human uvula.

The objective of this study was to investigate whether taste buds are present on the human adult uvula. Our goal was to determine whether surgical procedures that involve removal of the uvula are likely to affect taste perception.

Materials and methods

Five human uvulae were removed via a modified carbon dioxide (C[O.sub.2]) laser-assisted uvulopalatoplasty in an outpatient office setting in the Department of Otolaryngology--Head and Neck Surgery at Thomas Jefferson University. The five patients underwent surgery for the treatment of snoring and obstructive sleep apnea. Patients were seated in an upright position and administered topical anesthesia with 20% benzocaine. They were then injected with a combination of 1 ml of 0.5% bupivacaine and 2 ml of 2% lidocaine in 1 ml of 1:100,000 epinephrine. The injection was made along the junction of the soft palate and uvula and bilaterally along the junction of the anterior tonsillar pillar and palate. A Sharplan C[O.sub.2] laser set at 10 W Superpulse and a pharyngeal handpiece with a backstop were used to incise the free edge of the palate on either side of the uvula for a vertical distance of 2 to 3 cm. The uvula was grasped with an Allis clamp and transected at its root.

One of the patients, a 29-year-old woman with normal smell and taste function, volunteered to provide a tongue biopsy. A 1-[cm.sup.2] section of the anterior-dorsal surface of her tongue was infiltrated submucosally with 0.3 ml of 1% lidocaine. The biopsy specimen was taken from the upper half of the fungiform papillae in the anesthetized area with micro spring scissors.

Immediately after removal, the uvula and tongue specimens were placed in 4% paraformaldehyde in phosphate-buffered saline (PBS) with a pH level of 7.4 for 12 to 48 hours at 4[degrees] C. Specimens were then cryoprotected with sequential immersions in 10% sucrose in PBS for 24 hours, 20% sucrose in PBS for 24 hours, and 30% sucrose in PBS for 24 hours. Serial sections of each entire specimen were cut to 10 [micro]m on a Microm HM 500 OM cryostat at a temperature between -18[degrees] and -25[degrees] C. The tissue sections were thaw-mounted onto Superfrost Plus slides and placed on a slide warmer for 1 hour. Slides were stored at 4[degrees] C for no more than 72 hours.

We employed the lead (Pb) method for membrane- associated calcium adenosine triphosphatase (ATPase) detection. (3) Slides containing tissue sections were incubated for 10 minutes at room temperature in an incubating medium of 20 ml of 0.84 mmol ATPase, 20 ml of 80 mmol Tris-maleate buffer (p14: 7.2), 3 ml of 2% Pb(N[O.sub.3]) 2, 5 ml of 0.1 mol/L Mg(N[O.sub.3])2, and 2 ml of deionized water. After 10 minutes, the slides were dipped twice in deionized water, developed in 1% yellow ammonium sulfide for 1 minute, and then dipped twice again in deionized water. The slides were dried and cover-slipped. Brownish-black deposits indicating the presence of ATPase in the stained tissue sections were then examined under light microscopy.

Results

No ATPase-stained structure that resembled a taste bud was found on the surface epithelium of any uvula specimen (figure 1). The fungiform papillae, which served as the controls in this study, did show the presence of taste receptors on ATPase staining (figure 2). Taste buds are onion-shaped, multicellular organelles that project to the epithelial surface of the papilla.

Discussion

Taste disturbances have been reported by as many as 7% of patients who have undergone laser uvuloplasty or uvulopalatopharyngoplasty. (4) However, our study failed to show that taste buds are present on human uvula tissue. Our findings suggest that the taste disturbances noted after surgical procedures involving removal of the uvula are not attributable to a loss of taste receptors. We speculate that flavor appreciation in these patients might be altered by changes in retronasal airflow, resulting in a decreased presentation of odors to the olfactory mucosa.

References

(1.) Nilsson B. The occurrence of taste buds in the palate of human adults as evidenced by light microscopy. Acta Odontol Scand 1979;37:253-8.

(2.) Lalonde E, Eglittis J. Number and distribution of taste buds on the epiglottis, pharynx, larynx, soft palate and uvula in a human newborn. Anat Rec 1961;140:91-5.

(3.) Pease AGE. Histochemistry: Theoretical and Applied. 3rd ed., vol. I. London: J.A. Churchill: 1968.

(4.) Hagert B, Wikblad K, Odkvist L, Wahren L.K. Side effects after surgical treatment of snoring. ORL J Otorhinolaryngol Relat Spec 2000;62:76-80.

From the Department of Otolaryngology--Head and Neck Surgery, Thomas Jefferson University, Philadelphia (Dr. Ambro, Dr. Pribitkin, and Dr. Keane), and the Monell Chemical Senses Center, Philadelphia (Ms. Wysocki and Dr. Brand).

Reprint requests: Edmund A. Pribitkin, MD, Department of Otolaryngology--Head and Neck Surgery, Thomas Jefferson University, 925 Chestnut St., Sixth Floor, Philadelphia, PA 19107. Phone: [phone]; fax: [phone]; e-mail: [e-mail]

Originally presented as a poster at the combined otolaryngology spring meetings; Palm Desert, Calif.; April 24, 1999.