ECTOMIZED, OVARIECTOMIZED, ADRENALECTOMIZED RATS

In the hypophysectomized-ovariectomized-adrenalectomized hooded Norway rat, growth of the mammary ducts can be induced with oestrone + somatotrophin + corticoids; lobule-alveolar development ensues if in addition to the above combination progesterone + prolactin is also administered. On withdrawing these hormones the local injection of prolactin then causes secretion in the underlying mammary gland, but only when corticoids are administered systemically. It has been demonstrated by Lyons, Li & Johnson [1958] (see also review by Lyons[1958]) that the hormone combination of oestrogen, somatotrophin, deoxycorti¬ costerone acetate and a glucocorticoid will induce mammary duct growth in the triply-operated (hypophysectomized-ovariectomized-adrenalectomized) rat (Long-Evans strain). When, moreover, this hormone combination was supplemented with progesterone and prolactin full lobule-alveolar development occurred. Milk secretion could then be induced by stopping the injections of ovarian steroids and somato¬ trophin, while continuing those of prolactin and corticoids. It was deemed of interest to repeat and extend these studies in another strain of rat; and some observations on hooded Norway rats are reported below