Effect of Progesterone Alone and in Combination with either Corticosterone, 17ß-Estradiol or Insulin on Prolactin-stimulated Fatty Acid Synthesis in Mammary Explants from Pseudopregnant Rabbits

Abstract

Progesterone up to 15·9 ,u.mol/I progressively suppressed prolactin-stimulated fatty acid synthesis in cultured mammary explants from II-day pseudopregnant rabbits, but did not influence the proportion offatty acids of medium chain length (C80-C12 ;O). Greater sensitivity to progesterone inhibition was observed at the low end of the ranges of corticosterone (29 nmol/I) and insulin (4·2 nmol/I) concentrations in the culture medium, which suggests an interaction between the hormones. A range of from 0·0001 to 10 ,u.mol/I of 17 {3-estradiol concentrations had no effect on prolactin-stimulated fatty acid synthesis in the presence or absence of progesterone.