Abstract
Detection and metabolism of inositol-1, 2-cyclic-4, 5-trisphosphate (cIP3) were investigated in the thrombin-stimulated human platelets. The reaction of 32P-labeled platelets with thrombin were stopped by addition of CHCl3/MeOH. The water soluble fraction was applied on the Whatman Partisil-10 column chromatogrphy. The unknown radioactive peak of 32P was detected in the fraction between inositol-1, 4-diphosphate (IP2) and inositol-1, 4, 5-trisphosphate (IP3) in the chromatography. The unknown radioactive peak moved to IP3 position with the internal standard of 3H-cIP3 by acidification of the sample. Furthermore, the unknwon radioactive peak of 32P was collected and was treated with IP3-5-phosphatase. The radioactive peak moved to the position of cIP2. It indicates that in the thrombin-stimulated platelets, the radioactive compound of 32P detected between IP2 and IP3 fraction in the chromatography is cIP3.
Rabiolabeled inositolphosphates and inositol-cyclic-phosphates were incubated with the cytosol fraction of human pletelets. The 1, 2-ring of cIP3 was not cleaved immediatly after the production from platelets and the cIP3 did not convert to IP3 in the metabolic process. It indicates that cIP3 is metabolited as follow: cIP3→cIP2→cIP1→IP1.
