OBJECTIVETo investigate the influence of microtubule depolymerization of myocardial cells on distribution and activity of mitochondria, and energy metabolism of cells in adult rats.

METHODSMyocardial cells of SD adult rats and SD suckling rats were isolated and cultured. They were divided into adult and suckling rats control groups (AC and SC, normally cultured without any stimulating factor), adult and suckling rats microtubule depolymerization agent groups (AMDA and SMDA, cultured with 8 micromol/L colchicine containing nutrient solution for 30 minutes) according to the random number table. (1) The expression of polymerized beta tubulin in myocardial cells of adult and suckling rats was detected with Western blot. (2) Myocardial cells of rats in AC and AMDA groups were collected. The expression of cytochrome c was detected with Western blot. Distribution of voltage-dependent anion channels (VDAC) and polymerized beta tubulin in myocardial cells were observed with immunofluorescent staining. Mitochondrial inner membrane potential was determined with immunocytochemical method. Activity of myocardial cells was detected with MTT method. Contents of ATP, adenosine diphosphate (ADP), and adenosine monophosphate (AMP) and energy charge of cells were determined with high performance liquid chromatography.

RESULTS(1) The expression of polymerized beta tubulin:in AMDA group it was 0.52 + or - 0.07, which was obviously lower than that (1.25 + or - 0.12) in AC group (F = 31.002, P = 0.000); in SMDA group it was 0.76 + or - 0.12, which was significantly lower than that (1.11 + or - 0.24) in SC group (F = 31.002, P = 0.000), but was obviously higher than that in AMDA group (F = 31.002, P = 0.009). (2) The expression of cytochrome c in AC group was 0.26 + or - 0.03, which was obviously lower than that (1.55 + or - 0.13) in AMDA group (t = -24.056, P = 0.000). (3) Immunofluorescent staining result: in AC group, microtubules of myocardial cells were in linear tubiform, distributed in parallel with myocardial fiber; VDAC staining result showed that mitochondria were in granular form, distributed in the same direction as microtubules. In AMDA group, the normal distribution regularity of microtubules was destroyed, with weakened immune fluorescence intensity, microtubules structure indistinct, continuity lost, rough in appearance, and the distribution of mitochondria became disrupted. (4) Mitochondrial inner membrane potential in AC group fluorescent intensity was 1288 + or - 84, which was obviously higher than that (331 + or - 27) in AMDA group (t = 26.508, P = 0.000). (5) Cellular activity: in AC group absorbance value was 1.75 + or - 0.11, which was obviously lower than that (0.81 + or - 0.07) in AMDA group (t = 17.348, P = 0.000). (6) Energy metabolism: compared with those in AC group, content of ATP decreased, contents of ADP and AMP increased, and ATP/ADP value and energy charge decreased in AMDA group.

CONCLUSIONSMicrotubules and mitochondria distribute in the same direction in normal myocardial cells in adult rats. After microtubule depolymerization, mitochondria are arranged in disorder fashion; cytochrome c leaks from mitochondria; mitochondrial membrane potential, energy supply, and cellular activity decrease in the myocardial cells.