Decrease in an Inwardly Rectifying XXXX Conductance in @entity19 Mammary Secretory Cells after Forced Weaning.

@entity19 @entity3923 @entity8594 @entity2303 @entity972
UNASSIGNED: Mammary glands are physiologically active in female mammals only during nursing. Immediately after weaning, most lactation-related genes are downregulated and milk production ceases. In our previous study, we have detected an inwardly rectifying @entity972 channel (Kir) 2.1-like current in @entity3923 ( @entity3923 ) cells freshly isolated from lactating @entity19 . This current is highly sensitive to external @entity8594 . The @entity972 permeability of the Kir channels may contribute to the secretion and/or preservation of ions in milk. We hypothesized that the functions of the Kir channels in @entity3923 cells are regulated after weaning. To test this hypothesis, we examined the effect of forced weaning on the @entity8594 -sensitive Kir current and @entity2303 expression in the @entity19 mammary glands. Twenty-four hours after weaning, the lumina of mammary acini were histologically enlarged by milk accumulation. The whole-cell patch-clamp analyses showed that the @entity8594 -sensitive Kir current in the post-weaning @entity3923 cells was smaller than in the lactating @entity3923 cells. The inward conductances of the current in the lactating and post-weaning cells were 4.25    0.77 and 0.93    0.34 nS, respectively. Furthermore, real-time PCR and Western blot analyses showed that @entity2303 mRNA and protein expression decreased in the post-weaning mammary gland (mRNA, 90% reduction; protein, 47% reduction). Moreover, the local milk accumulation caused by teat sealing decreased Kir conductance in @entity3923 cells (2.74    0.45 and 0.36    0.27 nS for control and sealed mammary glands, respectively). This was concomitant with the reduction in the @entity2303 mRNA expression. Our results suggest that milk stasis after weaning immediately decreases the Kir conductance in @entity3923 cells. This decrease in the Kir conductance may be partly caused by the reduction in the @entity2303 mRNA and protein expression. These alterations during the post-weaning period may be involved in the cessation of ion secretion and/or preservation in the milk.
