Effects of digitoxin and hypokalaemia on pancreatic NaHCO3 secretion and pancreatic Na,K-ATPase activity.
To study the role played by Na,K-ATPase in the pancreatic secretion of NaHCO3, experiments were performed in 20 anaesthetized, secretin-infused pigs (3.0 clinical units X kg b. wt. X h-I). The relationship between pancreatic NaHCO3 secretion and arterial pH was obtained before and during Na,K-ATPase inhibition by digitoxin and hypokalaemia. Na,K-ATPase activity in pancreatic tissue homogenate averaged 5.45 (5.02-6.68) mumol Pi X mg X protein X h-I. Retrograde injection of 0.5 ml 1.4 X 10(-4) mol X l-I digitoxin into pancreatic ducts reduced pancreatic Na,K-ATPase activity by 3I(I8-47)%, while intra-arterial injection of 0.2 mg X kg b. wt-I digitoxin reduced pancreatic Na,K-ATPase activity by 50(45-56)%. Digitoxin and hypokalaemia reduced the rate of pancreatic NaHCO3 and shifted the normal, proportional relationship between NaHCO3 secretion and arterial pH towards higher pH. Hypokalaemia reduced Na,K-ATPase activity and NaHCO3 secretion in proportion. These effects indicate that Na,K-ATPase helps to sustain the requisite electrochemical potential gradients for driving H+ ions, and hence HCO-3 ions, out of secretory cells.
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Grotmol
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Buanes
O
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Mathisen
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Schistad
O M
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Sejersted
M G
MG
Raeder
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D004074:Digitoxin / Q000008:administration & dosage / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D007261:Infusions, Intra-Arterial; D007263:Infusions, Parenteral; D007267:Injections; D007473:Ion Channels; D010179:Pancreas / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D010183:Pancreatic Ducts; D011188:Potassium / Q000097:blood*; D011522:Protons; D012633:Secretin / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013552:Swine
D001639:Bicarbonates; D007473:Ion Channels; D011522:Protons; D012633:Secretin; D004074:Digitoxin; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium