Some functional and morphological characteristics of an acutely dispersed purified cell suspension of rat lactotrophs prepared with Percoll.

A cell suspension containing more than 90% lactotrophs can be prepared from enzymically dispersed adenohypophyses obtained from male rats pretreated with estradiol. The lactotrophs are separated from the mixed cell population by centrifugation on a discontinuous density gradient prepared from a commercial preparation of colloidal silica (Percoll, Pharmacia). The method allows isopycnic separation of these delicate cells under very mild conditions; normal ionic strength and normal pH were maintained throughout the gradient, centrifugal acceleration did not exceed 1600 X g, and all procedures were done at room temperature. Histological verification that at least 90% of the cells were lactotrophs was done using specific immunoperoxidase staining. The functional capability of the lactotrophs was established by measuring the dose--response to the dopamine agonist bromocriptine and to thyrotropin-releasing hormone (TRH). Bromocriptine decreased spontaneous release in a dose-related way over the concentration range of 10(-10) to 10(-8) M. TRH, which causes an in vivo release of prolactin (PRL) in estrogen-primed rats, produced a dose-related increase in the release of PRL over the concentration range of 3 X 10(-10) to 3 X 10(-8) M after the high spontaneous release had been previously reduced by bromocriptine (3 X 10(-8) M).