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 marker of type III collagen metabolism. The serum concentration of PIIINP is increased during inflammation, probably reflecting stimulated biosynthesis of type III collagen. Serum PIIINP decreases during glucocorticoid treatment. This has been interpreted as an inhibited biosynthesis of type III collagen. However, circulating PIIINP is extracted by the liver, and the decrease in serum PIIINP may also be caused by an increased hepatic elimination. In the present study we investigated the influence of intravenous methylprednisolone on the serum PIIINP level in pigs combined with a simultaneous determination of the hepatic extraction of PIIINP. The serum level of PIIINP decreased by approximately 30% within 2 h following glucocorticoid injection (p<0.01). The initial hepatic extraction ratio of PIIINP was 0.15 (range 0.05-0.33) and neither changed after administration of methylprednisolone nor differ from that of the controls. Injection of methylprednisolone did not influence the gel filtration profile. The results of this study confirm the previous finding of serum PIIINP being decreased following glucocorticoid administration, but disprove the hypothesis that alterations in the liver extraction of PIIINP explain the decrease.