STEREOSCOPIC ANALYSIS OF DISTRIBUTION OF MICROTUBULES AROUND THE CENTROSOME IN THE INTERPHASE PK CELLS AFTER TREATMENT WITH TAXOL AND NOCODAZOLE

In the interphase PK cells, more than 85% of microtubules radiating fr om the centrosome were not longer than 1,5 mu m. A half of the microtu bules had free proximal ends. After nocodazole treatment (20 mu M), th e number of microtubules attached to the centrosome decreased by 20% a fter 10 min of treatment, remained the same after 20 min of treatment, and increased after 60 min of nocodazole treatment slightly exceeding the control level. After 5 and 60 min of treatment, the number of att ached microtubules with the lengh over 0,7 mu m increased twice as com pared to the control level. During the first 20 min of nocodazole trea tment, the immunofluorescent staining of cells with antibody to gamma- tubulin was the same as in the control, but after 60 min of treatment, the centrosome was stained more intensively than in the control cells . The number of free microtubules decreased fourfold during the first 5 min, then it decreased slowly (for 10-20 min) and remained at the sa me low level after 60 min. After 10 min of taxol (12 mu M) treatment, the number of attached and free microtubules increased more than two t imes, whereas the number of attached microtubules with the lengh over 0,7 mu m increased more than tenfold. After 15 min of treatment, the n umber of attached microtubules was slightly higher, and the number of free microtubules was a half of the control level. After 20-60 min of treatment, the number of microtubules of all the types decreased. Thus , upon the nocodazole treatment, the microtubules attached to the cent rosome were more resistant to depolymerization; however these microtub ules were the most reactive to taxol treatment. The data obtained supp ort that a) in PK cells, the centrosome-attached microtubules occupied net all of the existing templates; b) during the longterm treatment w ith inhibitors, centrosome performed the compensatorly reaction - the inhibition of microtubule assembly results in the increase in the numb er of active templates on the centrosome; the inhibition of microtubul e depolymerization results in the inactivation of earlier activated re serve templates. Microtubules formed on the centrosome in the First mi nutes disengage from it and then leave the centrosomal region.