The opposite correlation between calcium ion and cyclic-AMP regarding the activation of microsomal triglyceride transfer protein in rat liver.
In this study, the effects of Ca(2+) and cyclic adenosine monophosphate (cAMP) on microsomal triglyceride (TG) transfer protein (MTP) activity were investigated in rat liver. MTP activity was high when liver contained low levels of cAMP, which was induced by administration of glucose, or high levels of total Ca(2+) and TG. However, MTP activity increased by high levels of Ca(2+) and TG was reduced in a dose-dependent manner by treatment with dibutyryl-cAMP (db-cAMP), a cAMP analogue. Conversely, when homogenates of liver from normal rats, with low levels of total Ca(2+) and high levels of cAMP, were incubated with thapsigargin, a Ca(2+)-inducer, MTP activity was increased in a dose-dependent manner compared to control. Therefore, our results suggest that high levels of Ca(2+) cause hypertriglyceridemia through the elevation of MTP activity, as opposed to high levels of cAMP, which suppress MTP activity and inhibit hypertriglyceridemia.
Cho
Hyun-Jeong
HJ
Department of Biomedical Laboratory Science, College of Medical Science, Konyang University, Daejeon 302-718, Korea.
Kim
Hyeong-Soo
HS
Yu
Young-Bin
YB
Kang
Hyo-Chan
HC
Lee
Dong-Ha
DH
Rhee
Man-Hee
MH
Cho
Jae-Youl
JY
Park
Hwa-Jin
HJ
D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism*; D005247:Feeding Behavior / Q000187:drug effects; D005947:Glucose / Q000008:administration & dosage / Q000494:pharmacology; D008099:Liver / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D019284:Thapsigargin / Q000494:pharmacology; D014280:Triglycerides / Q000378:metabolism
D002352:Carrier Proteins; D014280:Triglycerides; C106092:microsomal triglyceride transfer protein; D003994:Bucladesine; D019284:Thapsigargin; D000242:Cyclic AMP; D005947:Glucose; D002118:Calcium