Inhibition of mammary gland lactose secretion by colchicine and vincristine

Abstract

The possible role of microtubules in milk production was examined in mammary gland slices from lactating guinea pigs. Colchicine, 10(-5)-10(-4) M, depressed lactose secretion within 15 min, maintaining maximal inhibition over 2.5 h, accompanied by retention of lactose within the slices. In colchicine dose-response studies (2 h, 10(-8)-10(-5) M), secretion was depressed 22% by 10(-5) M, whereas tissue lactose increased with dose up to +25% at 10(-5) M. Lactose synthesis was inhibited 3-19% without correlation to colchicine concentration. In another study, incubation with 10(-5) M lumicolchicine yielded one-third less inhibition of secretion than 10(-5) M colchicine with no increase in tissue lactose. Both drugs depressed synthesis 31%. Lactose secretion showed a negative correlation with 10(-7)-10(-4) M vincristine yielding a maximal 66% inhibition at 10(-4) M, whereas tissue retention showed a linear increase with concentration up to 151% of control at 10(-4) M. Effects on synthesis were sporadic. These data suggest that microtubules have a role in facilitating the transport and/or secretion of lactose and perhaps other milk components.