GLUCOCORTICOIDS INHIBIT THE SYNTHESIS RATE OF TYPE-III COLLAGEN, BUT DO NOT AFFECT THE HEPATIC-CLEARANCE OF ITS AMINOTERMINAL PROPEPTIDE (PIIINP)

The aminoterminal propeptide of type III procollagen (PIIINP) is a mar ker of type III collagen metabolism. The serum concentration of PIIINP is increased during inflammation, probably reflecting stimulated bios ynthesis of type III collagen. Serum PIIINP decreases during glucocort icoid treatment. This has been interpreted as an inhibited biosynthesi s of type III collagen. However, circulating PIIINP is extracted by th e liver, and the decrease in serum PIIINP may also be caused by an inc reased hepatic elimination. In the present study we investigated the i nfluence of intravenous methylprednisolone on the serum PIIINP level i n pigs combined with a simultaneous determination of the hepatic extra ction of PIIINP. The serum level of PIIINP decreased by approximately 30% within 2 h following glucocorticoid injection (p<0.01). The initia l hepatic extraction ratio of PIIINP was 0.15 (range 0.05-0.33) and ne ither changed after administration of methylprednisolone nor differ fr om that of the controls. Injection of methylprednisolone did not influ ence the gel filtration profile. The results of this study confirm the previous finding of serum PIIINP being decreased following glucocorti coid administration, but disprove the hypothesis that alterations in t he liver extraction of PIIINP explain the decrease.