Suckling influences the in vitro assembly of anterior pituitary gland tubulin into microtubules in the lactating rat.

Microtubules in the lactating rat anterior pituitary gland were depolymerized into their constituent tubulin monomers by homogenizing the pituitary tissue at 4 degrees C. The optimal conditions for the assembly of the pituitary tubulin into microtubules were established. It was found that the extent of assembly at 37 degrees C and pH 6.8 increased as a function of protein concentration, was dependent upon the GTP concentration present in the assembly buffer, and was inhibited by cold, Ca2+, and tubulin antibody. Next, this method was used to determine whether suckling affected the extent to which anterior pituitary tubulin of the rat assembled into microtubules. The tubulin fraction from rats which were suckled for 30 min assembled into microtubules to a lesser extent than did that from nonsuckled controls. These results suggest that the tubulin fraction obtained from the suckled rats is impaired in its ability to polymerize into microtubules.