Hormonal regulation of medium chain fatty acid synthesis by mouse mammary gland explants

Abstract

AbstractExplants of pregnant mouse mammary tissue were cultured in media supplemented with various hormones. During the last few hours of culture, explants were labeled with [14C] acetate. Fatty acid synthesis by the tissue was analyzed using reverse phase thin layer chromatography, and incorporation of radioactivity into the medium chain fatty acid (MCFA) fraction was calculated as total MCFA per mg tissue fresh weight and as a percentage of the total fatty acid radioactivity (%MCFA). After 48 hr of culture, explants had an elevated %MCFA synthesis only when exposed to media containing insulin, cortisol and prolactin, confirming previous reports. Increasing doses of prolactin (maximal response at 300 mg/ml) caused a coordinate rise in both %MCFA synthesis and total MCFA synthesis per mg fresh weight. Epithelial cells isolated from explants after culture for 48 hr with insulin, cortisol and prolactin showed an elevated %MCFA synthesis compared to cells from explants cultured with insulin and cortisol alone, indicating that hormonal stimulation of mammary explants causes a change in the chain length of fatty acids synthesized by mammary epithelial cells. The specificity of the explant response to prolactin was tested with other hormones: FSH and calcitonin had no effect, whereas bovine growth hormone showed activity only at high concentration. Progesterone and 17β‐estradiol also had no effect. The analysis of MCFA synthesis provides another means of (a) assessing hormonal action upon mammary tissue, and (b) evaluating the biological activity of prolactin.