Objective. To study the characteristics of changes of LDH enzyme patterns of mice under slight hypoxia.Methods. Mice treated with artificial hypoxia

various tissues were made for the test of LDH enzymatic activity by the specific staining technique. LDH （1 -5） relative percentage enzymatic activity （RPEA） were measured with CS-910 dual-wavelength thin layer chromatography scanner.Results. The RPEA of LDH isozymes of various tissues after slight hypoxia shifted to the isozymes LDH1 and LDH2

whose principal subunits are H subunits

and the RPEA of LDH

（H4）

LDH2（H3M） increased

while RPEA of LDH5（M4） in various tissues decreased prominently except the cardiac muscle

and that of LDH4（HM3） decreased as well. After polyacrylamide gel electrophoresis （PAGE） of the hypoxia treated cardiac muscle specimen was made

activity subbands originated regularly in the isozyme patterns of LDH

with the regularity of LDH1 （0 subband）

LDH2 （0-1 subbands）

LDH3 （0-2 subbands）

LDH4 （1-3 subbands）

LDH5 （2-4 subbands）. After adding appropriate amount of NAD+ to the hypoxia treated cardiac muscle specimen

PAGE showed the subbands of four isozymes （LDH2-LDH5） reduced or even totally disappeared in the isozyme patterns.Conclusions. The negative feedback regulation of coenzymization and decoenzymization of LDH isozymes is one of the mouse stress responses to slight hypoxia.