Effects of Mg++ and Ca++ on water absorption from rodent and human intestine

Digestion. 1981;22(2):80-4. doi: 10.1159/000198599.

Abstract

The effect of the soluble chlorides of Mg++ and of Ca++ on intestinal water absorption was compared in rodents and in humans because Mg++ is a laxative while Ca++ is reputed to be constipating. In rats, net water transport in vivo from segments of jejunum or of colon was similar during control periods with NaCl, 275 mosm/kg, and during test periods when 40 mM CaCl2, or MgCl2 (made isoosmolal with NaCl) was infused. Both CaCl2 and MgCl2 depressed water absorption in ileal segments by 30-40% compared with NaCl. In man, 6 ileostomy patients were given 60 mmole CaCl2 or MgCl2, orally over 24 h for 3 days in a randomized, cross-over trial. CaCl2 increased the average ileostomy output from 984 to 1,336 g/day; MgCl2 increased output from 939 to 1,352 g/day. A corollary of these results was that magnesium hydroxide would be less effective laxative when this insoluble hydroxide is not converted to soluble chloride by gastric juice. To test this inference, 5 totally gastrectomized patients were given 60 mmole of Mg(OH)2 or MgCl2 daily. Stool weight increased by 136 g after MgCl2 but not after Mg(OH)2.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Body Water / metabolism*
  • Calcium Chloride / pharmacology*
  • Colon / metabolism
  • Gastrectomy
  • Gastric Juice / metabolism
  • Humans
  • Ileum / metabolism
  • Intestinal Absorption / drug effects*
  • Jejunum / metabolism
  • Magnesium / pharmacology*
  • Magnesium Chloride
  • Magnesium Hydroxide / administration & dosage
  • Magnesium Hydroxide / metabolism
  • Male
  • Rats
  • Rats, Inbred Strains

Substances

  • Magnesium Chloride
  • Magnesium
  • Calcium Chloride
  • Magnesium Hydroxide