Effects of Mg++ and Ca++ on water absorption from rodent and human intestine.
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.
D000818:Animals; D001834:Body Water / Q000378:metabolism*; D002122:Calcium Chloride / Q000494:pharmacology*; D003106:Colon / Q000378:metabolism; D005743:Gastrectomy; D005750:Gastric Juice / Q000378:metabolism; D006801:Humans; D007082:Ileum / Q000378:metabolism; D007408:Intestinal Absorption / Q000187:drug effects*; D007583:Jejunum / Q000378:metabolism; D008274:Magnesium / Q000494:pharmacology*; D015636:Magnesium Chloride; D008276:Magnesium Hydroxide / Q000008:administration & dosage / Q000378:metabolism; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains
D015636:Magnesium Chloride; D008274:Magnesium; D002122:Calcium Chloride; D008276:Magnesium Hydroxide