alkaline tide

{{Short description|Increase in blood pH after a meal}}

Alkaline tide (mal del puerco) refers to a condition, normally encountered after eating a meal, where during the production of hydrochloric acid by the parietal cells in the stomach, the parietal cells secrete bicarbonate ions across their basolateral membranes and into the blood, causing a temporary increase in blood pH.{{cite book|author1=Margaret E. Smith|author2=Dion G. Morton|title=The Digestive System: Systems of the Body Series|url=https://books.google.com/books?id=fEDJR6--3LkC|date=18 November 2011|publisher=Elsevier Health Sciences UK|isbn=978-0-7020-4841-8|page=52}}

During hydrochloric acid secretion in the stomach, the gastric parietal cells extract chloride anions, carbon dioxide, water and sodium cations from the blood plasma and in turn release bicarbonate back into the plasma after forming it from carbon dioxide and water constituents. This is to maintain the plasma's electrical balance, as the chloride anions have been extracted. The bicarbonate content causes the venous blood to leave the stomach more alkaline than the arterial blood delivered to it.

The alkaline tide is neutralised by the secretion of H⁺ into the blood during HCO₃⁻ secretion in the pancreas.{{cite book|author1=Margaret E. Smith|author2=Dion G. Morton|title=The Digestive System: Systems of the Body Series|url=https://books.google.com/books?id=fEDJR6--3LkC|date=18 November 2011|publisher=Elsevier Health Sciences UK|isbn=978-0-7020-4841-8|page=85}}

Postprandial (i.e., after a meal) alkaline tide lasts until the acids in food absorbed in the small intestine reunite with the bicarbonate that was produced when the food was in the stomach. Thus, the alkaline tide is self-limited and normally lasts less than two hours.

Postprandial alkaline tide has also been shown to be a causative agent of calcium oxalate urinary stones in cats,{{cite journal |first1=DF |last1=Taton |last2=Hamar |first2=D |last3=Lewis |first3=LD |title=Evaluation of ammonium chloride as a urinary acidifier in the cat |journal=Journal of the American Veterinary Medical Association |date=15 February 1984 |volume=184 |issue=4 |pages=433–6 |pmid=6698874 }} and potentially in other species.McGavin, MD., Zachary, JF. Pathologic Basis of Veterinary Disease, Fourth Edition, Mosby, 2007, pp. 680–686.

A more pronounced alkaline tide results from vomiting, which stimulates the hyperactivity of gastric parietal cells to replace lost stomach acid.{{verification needed|date=August 2015}} Thus, protracted vomiting can result in metabolic alkalosis.{{cite journal|title= The generation and maintenance of metabolic alkalosis|volume=1|issue= 5|doi=10.1038/ki.1972.43|journal=Kidney International|pages=306–321|year= 1972|last1= Seldin|first1= Donald W.|last2= Rector|first2= Floyd C.|pmid= 4600132|doi-access= free}}