MELATONIN INHIBITS MAMMARY-GLAND DEVELOPMENT DURING PREGNANCY

Our objectives were: a) to determine whether melatonin (aMT) could inh ibit physiological mammary gland development during pregnancy and, b) to study the features of aMT binding sites in mammary tissue from preg nant mice. We conclude that: a) aMT (200 mu g/day), administered to mi ce during pregnancy, significantly inhibits the growth of mammary glan ds at the end of this period and, b) that the mammary tissue of pregna nt mice has binding sites for 2-[I-125]-iodomelatonin (affinity, K-d = 1.24 +/- 0.14nM; density, B-max = 40.6 +/- 1.8 fmol/mg protein) which display light/darkness differences with the highest K-d and the lowes t B-max at the end of the period of darkness.