Cellular Physiology of Secretion and Absorption

1
Cellular Physiology of Secretion and Absorption
Jack L. Leonard 2004
Johnson Chap. 34-35
2
Daily Secretion of Digestive Fluids
Fluid Volume (ml/day) pH
Saliva 1000-1200 6.0-7.0
Stomach (gastric secretion) 2000-3000 1.0-3.5
Pancreas (exocrine secretion) 1200-2000 8.0-8.3
Bile secretion 600-700 7.8
Brunners gland secretion 50 8.0-8.9
Succus entericus (intestinal juice) 2000-3000 7.8-8.0
Large intestine 60 7.5-8.0
Johnson Chap. 34-35
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Basic Secretory Mechanisms
Outside
Inside
(Gut lumen)
(interstitial space)
Na
Na
P
K
Na
K
K
Basolateral membrane
Apical membrane
Johnson Chap. 34-35
Redrawn from Acta Physiologica Scand. 42298, 1958
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Apical Surface
Apical Membrane
Johnson Chap. 34-35
Johnson Chap. 34-35
5
Basolateral Surface
Na
Active Transporter
ATP
K
Johnson Chap. 34-35
Johnson Chap. 34-35
Johnson Chap. 34-35
6
Na Pump Transport Rate
40
30
Transport Rate
20
10
5
10
15
20
Na (mM) (Intracellular)
Johnson Chap. 34-35
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Salt Secretion
Salt Absorption
interstitial space
interstitial space
Gut lumen
Gut lumen
Cl-
Cl-
Na
Johnson Chap. 34-35
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Salivary Duct Cell
Saliva
Plasma
100
Na
80
60
Ion concentration (mM)
40
HCO3
Cl
20
K
4
0
1
2
3
Flow (ml/min)
Johnson Chap. 34-35
9
Salivary Acinar Cell
stimuli
Secretion of Na, K, and Cl-
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Salivary Duct Cell
Serosal surface
K
Na
ATP
Na
K
H
CO2
CO2
H2CO3
HCO3-
Na K Cl- HCO3-
Na K Cl-
Lumen
Cl-
Na
Johnson Chap. 34-35
Johnson Chap. 34-35
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Salivary Duct Cell
Saliva
Plasma
100
Na
80
60
Ion concentration (mM)
40
HCO3
Cl
20
K
4
0
1
2
3
Flow (ml/min)
Johnson Chap. 34-35
12
Pancreatic Secretion
160
Na
HCO3-
120
Ion Concentration (mM)
80
40
Cl-
K
0
300
0
100
500
Secretion rate (ml/hr)
Johnson Chap. 34-35
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Intestinal Absorbing Cell
Serosal surface
K
Na
ATP
K
HCO3-
Cl
Cl
K
Cl-
Cl-
Na
Na
glucose
Lumen
Johnson Chap. 34-35
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Intestinal Secretory Cell
Serosal surface
Na
Na
Cl-
K
Na
K
Na
stimuli
ATP
K
Cl-
Cl-
Lumen
Johnson Chap. 34-35