Mammary Fat Can Adjust Prolactin Effect on Mammary Epithelial Cells via Leptin and Estrogen
Figure 5
Cholesterol secretion to the medium by mammary gland explants. (a) Effect of estrogen on cholesterol secretion to the medium from mammary explants culture. Bovine mammary explants from a lactating cow were incubated in medium containing insulin at 1 g mL-1, with or without estrogen at 200 ng mL-1. The secretion of cholesterol to the medium in which explants were incubated with insulin was 14.5 g mL-1 per milligram of tissue; addition of estrogen to the medium containing insulin elevated the cholesterol secretion to level of 20 g mL-1 per milligram of tissue. Results are least squares means ± SE (n = 4). Bars with different letters differ at P < .05. (b) Effects of prolactin, leptin, and leptin antagonist on cholesterol secretion to the medium from mammary explants culture. Bovine mammary explants from a lactating cow were incubated in medium with or without prolactin at 1 g mL-1, with or without leptin at 100 ng mL-1, or with a combination of leptin at 100 ng mL-1 and prolactin at 1 g mL-1, with or without leptin antagonist. Addition of leptin to the medium did not affect the secretion of cholesterol to the medium. Prolactin at a concentration of 1 g mL-1 elevated the secretion of cholesterol 16 g mL-1 per milligram of tissue. A combination of leptin at 100 ng mL-1 and prolactin at 1 g mL-1 elevated the secretion of cholesterol to its highest level of 19 g mL-1 per milligram of tissue. Addition of leptin antagonist to the leptin plus prolactin combined treatment down-regulated the secretion of cholesterol to 13.2 g mL-1 per milligram of tissue. Results are least squares means ± SE (n = 3). Bars with different letters differ at P < .05.
