C. Aceves et al., Mammary type I deiodinase is dependent on the suckling stimulus: Differential role of norepinephrine and prolactin, ENDOCRINOL, 140(7), 1999, pp. 2948-2953
Mammary deiodinase type I(M-D1) is present only during lactation and exhibi
ts a clear direct correlation with lactation intensity (size of litters). T
he present work shows that M-D1 is suckling dependent and that intervals be
tween suckling periods no longer than 12 h are essential to maintain this a
ctivity. Moreover, we find that with only 15 min of resuckling in 12-h nons
uckled mothers, the 50% decrease in both M-D1 messenger RNA and enzymatic a
ctivity could be restored to control values. This restorative effect by suc
kling may involve pre- and posttranscriptional mechanisms in which norepine
phrine and PRL play important roles. Norepinephrine elicits a potent stimul
atory effect on M-D1 messenger RNA and enzyme activities, whereas PRL only
increases M-D1 activity and may modulate the enzyme response to norepinephr
ine. Oxytocin and GH had no effect. These data suggest that the adrenergic
nervous system and PRL could directly participate in mammary energetic expe
nditure, regulating the local T-3 supply.