CHARACTERIZATION OF 16-KILODALTON TO 20-KILODALTON (KDA) CONNECTIVE-TISSUE GROWTH-FACTORS (CTGFS) AND DEMONSTRATION OF PROTEOLYTIC ACTIVITYFOR 38-KDA CTGF IN PIG UTERINE LUMINAL FLUSHINGS

Connective tissue growth factor (CTGF) is a growth and chemotactic fac tor for fibroblasts encoded by an immediate early gene that is transcr iptionally activated by transforming growth factor beta. Although the primary translational product of the pig CTGF gene is predicted to be of approximate M-r 38 000, pig uterine luminal flushings (ULF) contain ed 10- to 20-kDa CTGF proteins that were heparin-binding and mitogenic , whereas 38-kDa CTGF was not apparent. The N-termini of two microhete rogeneous forms of 16-kDa CTGF, as well as 18-kDa and 20-kDa forms of CTGF, commenced at, respectively, Cys(199), Ala(197), Asp(186), and As p(186) and did not correspond to intron-exon boundaries in the CTGF ge ne. Northern blotting revealed a single porcine (p) CTGF transcript of 2.4 kilobases in endometrium from Day 10 to 16 cycling or pregnant pi gs. Ten- to twenty-kilodalton pCTGF proteins in ULF were stable for 48 h at 37 degrees C whereas native 38-kDa pCTGF was degraded within 10 min under the same conditions. CTGF-degrading activity in pig ULF was heat-sensitive and concentration- and time-dependent. Ten- to twenty-k ilodalton CTGF levels in ULF peaked on Day 16 of the cycle and on Day 12 of pregnancy and were highly correlated with the levels of proteoly tic activity for 38-kDa CTGF. Collectively these data suggest that bio active 10- to 20-kDa CTGF proteins are generated in utero through limi ted proteolysis of the 38-kDa CTGF primary translational product.