Cartilage sulfation inhibitor from rat liver curtails growth of embryonic chicken cartilage in vitro

We studied the effect of high MW cartilage sulfation (somatomedin) inhibitors from rat liver on cartilage growth in vitro. Pelvic rudiments from 11-day-old chicken embryos (5.70 mg average weight) were incubated in an organ-culture system with defined tissue-culture medium; after two days (T0–2), media were changed and incubation continued for another three days (T2–5). Normal rat serum (10% vol/vol) stimulated cartilage growth (weight change + 1.33 ± 0.16 mg, mean ± SEM T0–2 and + 1.33 ± 0.27 mg, T2–5). Partially purified cartilage sulfation inhibitors (CSI) caused a weight decrease (− 1.09 ± 0.17 mg T0–2 and −0.44 ± 0.06 mg T2–5). Adding inhibitors to cartilage incubations containing normal serum abolished the growth-promoting effect of serum (−0.79 ± 0.07 mg T0–2 and −0.40 ± 0.08 mg T2–5). The growth-curtailing effect of CSI was reversible; after preincubating cartilage with CSI for two days (−0.62 ± 0.11 mg T0–2), subsequently exposing it to normal serum allowed cartilage growth to resume (+ 1.02 ± 0.21 mg T2–5). Cartilages incubated with normal serum and various concentrations of inhibitor exhibited a dose-dependent inhibition of serum-stimulated growth. Cartilage Length was not altered by the inhibitor; cartilage dry:wet weight ratio or protein concentration (μg/mg wet weight) did not differ among groups. Triodothyronine (T3) stimulated cartilage growht in a dose-dependent manner as expected. Adding CSI to cartilage incubations containing T3 (1.5 nmol/l or 15 nmol/L) completely abolished the growth-stimulating effect of T3. This is the first demonstration that high MW cartilage sulfation inhibitors from rat liver cause a dose-dependent and reversible inhibition of the growth of embryonic chicken cartilage in vitro; their ability to inhibit both serum- and T3-stimulated growth suggests that they exert broad, antianabolic effects.