Changes of plasma concentrations of PIIINP and PICP after myocardial infarction and their relationship to the content of myocardial collagen in rat

Objective:PⅢNP is the aminoter mi nal peptide released by the type Ⅲ procollagen when it is released into the int erstitial space and is digested by the endopeptidase, and PⅠCP is the carboxyte rminal peptide of type Ⅰ procollagen when it is digested and released. Measurin g the content of PⅢNP and PⅠCP in plasma has been used to evaluate the degree of myocardial fibrosis in hypertension and heart failure. Collagen deposition is a significant feature of replacement fibrosis and left ventricular remodeling a fter acute myocardial infarction (MI). But it is unknown weather or not PⅢNP an d PⅠCP could reflect the collagen deposition in infarct zone (IZ) and non-IZ a fter MI. Method: Rat model of MI was established by ligation of lef t main coronary artery. These rats were killed at 1, 3, 7, 14 and 42 days after the operation, and IZ and non-IZ tissues were obtained. PⅢNP and PⅠCP were me asured by radioimmunoassay and myocardial collagen contents were measured by hyd roxyproline test. Result: The results showed that plasma PⅢNP and PⅠCP beg an to increase 3 days after operation, reached peak at 14 days, and decreased at 42 days with the PⅢNP remained higher than those in sham group. Collagen conte nts in IZ and non-IZ began to increase at 3 days after operation, gradually inc reased thereafter with more significant increase in IZ. Correlated analysis foun d that there was no significant correlation between plasma PⅢNP or PⅠCP and le ft ventricular collagen content in the sham operation group. Plasma concentratio n correlated significantly to the collagen content in IZ (r= 0.68; P 0.01), but not to those in non-IZ (r= 0.16, P 0.05); plas ma PⅠCP also correlated significantly to the IZ collagen content (r= 0.52 , P 0.01) and to the non-IZ collagen content (r= 0.43, P 0.05) in MI group.Conclusion: The results suggest that changes of plasma con tents of PⅢNP and PⅠCP after MI mainly reflect collagen synthesis in IZ, and c orrelated poorly to the collagen content in non-IZ.