Abstract
Abstract
The microtubule (MT) protein, tubulin, was measured in mammary gland biopsies from 23 guinea pigs averaging four samples per animal from about 20 days antepartum through weaning. [3H]Colchicine binding assays were carried out on supernatants from tissues homogenized sequentially in MT-stabilizing and MT-depolymerizing buffers which yielded estimates, respectively, of free (S-1) and microtubular (S-2) tubulin as well as total tubulin (S-1 + S-2). There is almost a threefold increase in total tubulin which begins about 20 days antepartum and reaches a peak by 11 to 15 days postpartum. There is an initial increase in free tubulin, also beginning about 20 days antepartum; however, about 1 week before birth, free tubulin levels off and microtubular tubulin begins to increase, reaching a peak in midlactation after a sevenfold increase from pregnancy and then declining at weaning. The results show that free tubulin is synthesized in late pregnancy and then converted to the assembled (microtubular) state, which suggests that microtubules are involved in the lactation process.
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