Inhibition of casein and fat synthesis and α-lactalbumin secretion by progesterone in explants from bovine lactating mammary glands

Abstract

The effect of progesterone on casein and fat synthesis, on alpha-lactalbumin secretion and on accumulation of casein mRNA was studied in explants from bovine lactating mammary glands, cultured in the presence of insulin, cortisol or prolactin. All four biological activities were inhibited down to or below the level obtained in medium without prolactin. However, inhibition was only achieved by using concentrations of progesterone exceeding by 1000-fold those required for similar effects in tissue from non-lactating animals. A similar inhibitory effect was also found using high levels of other steroids without 11 beta-hydroxyl, such as deoxycorticosterone and dehydroepiandrosterone, and to some extent with oestradiol-17 beta, but not with cortisol or corticosterone. The inhibition by progesterone did not result from a decrease in explant viability, as determined by glucose uptake.

Effect of Insulin-Like Growth Factor I on Deoxyribonucleic Acid Synthesis and Galactopoiesis in Bovine Undifferentiated and Lactating Mammary Tissuein Vitro*

“…Our in vitro experiments have proved that these activities are sensitive to the action of lactogenic hormones (10,14).…”

Effects of cooling dry cows under heat load conditions on mammary gland enzymatic activity, intake of food and water, and performance during the dry period and after parturition

“…Explants were prepared as previously described (Shamay et al, 1987). Total RNA was isolated from the mammary tissue explants by the acid guanidinium thiocyanate phenol-chloroform extraction method (Chomczynski and Sacchi, 1987).…”

Mammary Fat Can Adjust Prolactin Effect on Mammary Epithelial Cells via Leptin and Estrogen

“…Explants were prepared as previously described [27]. Twenty explants, 50–80 mg total weight from a one udder quarter, were placed on an impregnated lens paper floating in 5 mL of M-199 medium, and cultured at 37°C in a medium supplemented with insulin at 1  μ g mL −1 , cortisol at 0.5  μ g mL −1 and prolactin at various concentrations (IFP).…”