The hormonal control of ovine beta-lactoglobulin gene in cultured ewe mammary explants

Mammary explants from pregnant ewes were cultured in the presence of insulin, cortisol and prolactin, either alone, or in combination. After 2 d of culture, total RNA was extracted from explants and the content of beta-lactoglobulin mRNA was estimated using a specific labelled cDNA probe. The mRNA for beta-lactoglobulin was only deinduced slowly in the absence of hormone during the culture. Prolactin alone induced the accumulation of the mRNA. Insulin and cortisol added together were also stimulatory, but they only moderately amplified the prolactin effect. Beta-lactoglobulin gene in ewes, is therefore, controlled by the lactogenic hormones which also induce casein gene expression. The amplitude of the stimulation was unexpectedly low. This seems due in part to the fact that the gene was only deinduced weakly. In this respect, beta-lactoglobulin gene appears to be less dependent on lactogenic hormones under these experimental conditions than casein genes.