Abstract
Summary
Growth hormone preparations from several mammalian species were investigated for their ability to initiate secretion in organ cultures of prelactating mammary tissue from strain C3H and A mice. All the growth hormones studies showed some degree of activity in C3H mammary tissues. Bovine, ovine and porcine GH were 20-50% as active as ovine prolactin, although the prolactin content of the preparations was shown to be low. Simian and human GH, whose prolactin-like activity in other systems is well-known, showed activity equal to or greater than ovine prolactin in C3H mammary tissues. On the other hand, a single human GH preparation (one of three studied) was the only GH to show significant activity in strain A mammary tissues. These results suggest an intrinsic lactogenic activity of GH, particularly well-marked in the case of human GH, whose expression in mouse mammary gland cultures is in part determined by the genetic background of the tissues.
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