TY - JOUR
T1 - Effect of phorbol and bryostatin I on chondrogenic expression of chick limb bud, in vitro
AU - Garrison, James C.
AU - Pettit, George R.
AU - Uyeki, Edwin M.
N1 - Funding Information:
This work was supported by CDC grant no. OH-1630 and NIEHS training grant no. ES-07079. The ASU-CRI component received financial support from the Fannie E. Rippel Foundation, the Arizona Disease Control Research Commission, the Robert B. Dalton Endowment Fund, and NCI Grants CA-16049-07-08 and 09. For assistance in isolation/preparation of Bryostatin I we wish to thank Drs. P. M. Blumberg, C. L. Herald, J. Leet and Y. Kamano.
PY - 1987/10/26
Y1 - 1987/10/26
N2 - The ability of phorbol esters to promote tumor formation and alter cell differentiation has been attributed to its action on a number of critical cellular functions, in particular, on protein phosphorylation, through the activation of protein C kinase. The present paper describes the effects of PMA (phorbol 12-mristate 13 acetate) on in vitro chondrogenesis in non-passaged, embryonic limb bud cells, relative to the effects of Bryostatin I. This compound also activates C kinase and binds competitively to the phorbol ester receptor, yet does not affect cell differentiation. Levels of PMA as low as 10-7 M markedly reduced cartilage formation in 4-day cultures, as indicated by nodule count and Alcian blue staining for chondroitin sulfate. Coadministration of Bryostatin I at equimolar concentration prevented the PMA inhibitory effect on chondrocytic expression. This confirms other findings that phorbol activation of C kinase cannot exclusively account for the activity of phorbol on cell expression, i.e., that other pathway (s) must also be involved. Altering the time of PMA exposure demonstrated that PMA inhibited chondrocyte phenotypic expression, rather than cell commitment: early (0-48 h) exposure to PMA (during chondrocytic commitment in vitro) had little inhibitory effect on the staining index, whereas, exposure from 49-96 h (presumably post-commitment) and 0-96 h had moderate and strong inhibitory effects, respectively, on cartilage synthesis. Further research on the phorbol/Bryostatin I interaction should add to our knowledge of the control processes involved in tumor promotion and cell differentiation.
AB - The ability of phorbol esters to promote tumor formation and alter cell differentiation has been attributed to its action on a number of critical cellular functions, in particular, on protein phosphorylation, through the activation of protein C kinase. The present paper describes the effects of PMA (phorbol 12-mristate 13 acetate) on in vitro chondrogenesis in non-passaged, embryonic limb bud cells, relative to the effects of Bryostatin I. This compound also activates C kinase and binds competitively to the phorbol ester receptor, yet does not affect cell differentiation. Levels of PMA as low as 10-7 M markedly reduced cartilage formation in 4-day cultures, as indicated by nodule count and Alcian blue staining for chondroitin sulfate. Coadministration of Bryostatin I at equimolar concentration prevented the PMA inhibitory effect on chondrocytic expression. This confirms other findings that phorbol activation of C kinase cannot exclusively account for the activity of phorbol on cell expression, i.e., that other pathway (s) must also be involved. Altering the time of PMA exposure demonstrated that PMA inhibited chondrocyte phenotypic expression, rather than cell commitment: early (0-48 h) exposure to PMA (during chondrocytic commitment in vitro) had little inhibitory effect on the staining index, whereas, exposure from 49-96 h (presumably post-commitment) and 0-96 h had moderate and strong inhibitory effects, respectively, on cartilage synthesis. Further research on the phorbol/Bryostatin I interaction should add to our knowledge of the control processes involved in tumor promotion and cell differentiation.
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U2 - 10.1016/0024-3205(87)90480-2
DO - 10.1016/0024-3205(87)90480-2
M3 - Article
C2 - 3118121
AN - SCOPUS:0023507144
SN - 0024-3205
VL - 41
SP - 2055
EP - 2061
JO - Life Sciences
JF - Life Sciences
IS - 17
ER -