Single Gland Studies of Esophageal Gland Secretion

We developed an in situ optical method to quantify and collect single gland secretions directly from ductal orifices of each gland. A freshly harvested porcine proximal esophageal ring is cut off, opened, dissected free from underlying musculature and mounted mucosal side up at the air‐liquid interface or mounted in an Ussing chamber. The surface is cleaned, dried, and coated with water‐saturated mineral oil. Mucus secretion from glands within the oil‐covered area forms spherical droplets that are digitally imaged at intervals and secretion rates calculated. Esophageal glands secreted basally at 0.35 nl/min/gland (119 glands, n=11 from 7 pigs) (I sc = 0.5 ± 0.1 μA/cm 2 ). We discovered that 10 μM forskolin, stimulate gland secretion: there was an initial (30~50 min) slow phase of mucus secretion at 0.53 ± 0.12 nl/min/gland (114 glands, n=10 from 7 pigs) followed by faster sustained secretion of 1.18 ± 0.23 nl/min/gland (114 glands, n=10 from 7 pigs). Secretion to carbachol peaked at 17.25 ± 6.26 nl/min/gland (103 glands, n=10 from 7 pigs) (ΔI sc = 0.9 ± 0.3 μA/cm 2 ) within 10 min and then declined to a sustained phase of 4.24 ± 1.69 nl/min/gland (58 glands, n=6 from 5 pigs) (ΔI sc = 0.3 ± 0.1 μA/cm 2 ). Atropine pretreatment abolished responses to carbachol but not to forskolin. H & E staining of paraffin embedded esophageal tissue sections revealed that acini are comprised of about 11% serous cells and 89% mucous cells. Repeated reverse transcriptase‐PCR failed to detect evidence of transcripts for CFTR from pig esophageal glands. These results suggest that esophageal gland secretes mucus in response to forskolin via non‐CFTR dependent pathway(s).