embryonic chick calvaria were exposed to skeletal effectors ( including high and low ph , a range of [ pi ] and [ ca ] , pth , naf , etc ) , and collagen formation was assessed by the incorporation of 3 [ h ] -proline as 3 [ h ] -hydroxyproline ( 3 [ h ] -hyp ) .
C0033382
proline
C0020388
hydroxyproline