Journal article
The effects of high-nutrient urea on in vitro bullfrog fundic mucosa
The Journal of surgical research, Vol.41(4), pp.445-455
1986
DOI: 10.1016/0022-4804(86)90060-0
PMID: 3095589
Abstract
The effects of nutrient urea (240 m
M) on H
+ secretion, potential difference, and resistance were studied in isolated sheets of bullfrog fundic mucosa. H
+ secretion was significantly reduced while transmucosal resistance was significantly increased and potential difference was significantly decreased. Measurement of CO
2 utilization by, and distribution across, the mucosal sheets demonstrated that oxidative metabolism is increased (tCO
2, 4.93 ± 0.2 to 5.83 ± 0.3 μmole/cm
2 hr
−1,
P < 0.05) and that generation of protons (H
+) within the oxyntic cell is stimulated (ΔCO
2, 1.48 ± 0.1 to 2.22 ± 0.2 μmole/cm
2 hr
−1,
P < 0.05, and nutrient HCO
3
− 1.35 ± 0.2 to 2.21 ± 0.2 μeq/cm
2 hr
−1,
P < 0.05) in spite of paradoxically diminished H
+ appearance on the secretory surface. Studies using 120 and 60 m
M urea suggest that the effects may be done dependent. Results with 240 m
M sucrose on the nutrient surface would indicate that those seen with urea cannot be attributed entirely to the hyperosmolality. Pretreatment of the mucosal sheets with metiamide (10
−3
M) resulted in the expected decrease in titratable H
+ (to 0) but had no effect on urea-stimulated oxidative metabolism (tCO
2, 2.09 ± 0.2 to 2.91 ± 0.4 μmole/cm
2 hr
−1,
P < 0.02) or the generation of protons by the oxyntic cell (ΔCO
2, 0.68 ± 0.1 to 1.35 ± 0.3 μmole/cm
2 hr
−1,
P < 0.02, and nutrient HCO
3
− 0.83 ± 0.1 to 1.65 ± 0.3 μeq/cm
2 h
−1,
P < 0.05). Both simultaneous or subsequent treatment with theophylline (5 × 10
−3
M) reversed the inhibitory effect of urea on H
+ secretion. Transmission electron microscopy revealed involution of the secretory membrane following treatment with urea but maintenance of the microvillous secreting configuration of the membrane when theophylline was added to the nutrient solution. These results suggest that although nutrient urea stimulates the generation of H
+ within the cell it simultaneously inhibits release of H
+ by the secretory membrane. Failure to inhibit urea-stimulated generation of H
+ within the cell by metiamide indicates that the increased oxidative metabolism and generation of protons stimulated by nutrient urea is probably not histamine-mediated. It is suggested that urea inhibits adenylyl cyclase and thus cAMP-mediated evolution of the secretory membrane with reduced H
+ transport, an effect that can be reversed by inhibiting phosphodiesterase with theophylline.
Details
- Title: Subtitle
- The effects of high-nutrient urea on in vitro bullfrog fundic mucosa
- Creators
- John G Allison - Departments of Surgery, Veterans Administration Medical Center and Medical University of South Carolina Charleston, South Carolina, USAJoseph J Cullen - Departments of Surgery, Veterans Administration Medical Center and Medical University of South Carolina Charleston, South Carolina, USAJames R Olney - Departments of Surgery, Veterans Administration Medical Center and Medical University of South Carolina Charleston, South Carolina, USA
- Resource Type
- Journal article
- Publication Details
- The Journal of surgical research, Vol.41(4), pp.445-455
- Publisher
- Elsevier Inc
- DOI
- 10.1016/0022-4804(86)90060-0
- PMID
- 3095589
- ISSN
- 0022-4804
- eISSN
- 1095-8673
- Language
- English
- Date published
- 1986
- Academic Unit
- Surgery; Radiation Oncology
- Record Identifier
- 9984051550902771
Metrics
26 Record Views