Effects of poly-gamma-glutamic acid on calcium absorption in rats.
The effects of poly-gamma-glutamic acid (gamma-PGA) on calcium (Ca) bioavailability and Ca content in bone were examined in female rats. Increases in in vitro Ca solubility was observed with increases in the amount of gamma-PGA. Acute studies showed that gamma-PGA increased the amount of soluble Ca in the small intestine. In a plasma-Ca kinetic experiment, gamma-PGA stimulated Ca absorption 20 min after administration, and the duration of absorption was approximately 2 h. In an acute intestinal transit experiment, gamma-PGA markedly increased intestinal transit in mice. In a chronic Ca-balance experiment, the results showed that gamma-PGA significantly increased the apparent Ca absorption, apparent Ca balance, bone density, and bone Ca content in rats. In the same experiment, gamma-PGA was also found to decrease the amount of soluble Ca in the small intestine, especially in the proximal small intestine, and to increase calbindin-D9k mRNA expression in the proximal small intestine in rats. In a chronic intestinal transit experiment, gamma-PGA decreased intestinal transit in mice. These results suggest that gamma-PGA increased Ca solubility, thereby enhancing Ca absorption in rats in the acute phase. In addition, chronic administration of gamma-PGA to rats increased the apparent Ca balance and bone Ca content. The active transcellular pathway in the proximal small intestine was the major mechanism by which these effects were exerted.
Yang
Li-Chan
LC
Department of Pharmacology, China Medical University, Taichung, Taiwan, ROC. wclin@mail.cmu.edu.tw
Wu
Jin-Bin
JB
Ho
Guan-Huei
GH
Yang
Shih-Ching
SC
Huang
Yun-Pen
YP
Lin
Wen-Chuan
WC
D000042:Absorption / Q000187:drug effects; D000818:Animals; D001682:Biological Availability; D015519:Bone Density / Q000187:drug effects; D001842:Bone and Bones / Q000187:drug effects* / Q000378:metabolism*; D064026:Calbindins; D002118:Calcium / Q000032:analysis / Q000378:metabolism* / Q000493:pharmacokinetics; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D007413:Intestinal Mucosa / Q000378:metabolism; D007422:Intestines / Q000187:drug effects; D007700:Kinetics; D011099:Polyglutamic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D064030:S100 Calcium Binding Protein G / Q000235:genetics; D012995:Solubility / Q000187:drug effects
D064026:Calbindins; D012333:RNA, Messenger; D064030:S100 Calcium Binding Protein G; C576507:S100g protein, mouse; C576508:S100g protein, rat; D011099:Polyglutamic Acid; D002118:Calcium