No abstract

A new technique is described for the study of mammalian pituitary cells in vivo and in vitro. The method involves encapsulation of freshly trypsinized rat, sheep or human pituitary cells in XM-50 Amicon hollow fibers followed by their intracranial implantation into hypophysectomized rats. These pituitary fiber units promoted recipient growth for ∼3 weeks before weight gains plateaued. Body composition analyses showed that significant quantities of protein, fat and ash accounted for the weight gain. Morphological study of the capsule contents 7–39 days postimplantation revealed the presence of intact somatotrophs and corticotrophs. The hollow fibers may provide an immunologically privileged site by virtue of the fact that the 50,000 dalton pores making up the lumen surface permit pituitary hormones to diffuse from the capsule, but theoretically do not permit immunoglobulin molecules to penetrate the capsule. Growth of hypox rats receiving capsules containing allogeneic rat pituitary cells, sheep cells or pieces of human postmortem pituitary support this concept. Furthermore, rats implanted with human PRL adenoma cells had detectable quantities of circulating hPRL 100 days post-implantation. It is suggested that the pituitary hollow fiber units function when they come in contact with a ventricular surface of a hypox animal. With these units, it will be possible to study function of the same group of pituitary cells in vitro and in vivo.

No abstract

Body weights of Snell (dw/dw) and Ames (df/df) dwarf mice doubled after intracranial implantation of hollow fiber units containing mouse pituitary cells. Recipients showed increased long bone growth, increased fat deposition, and marked loss of body hair. Recipients injected with thyroxine grew but did not develop increased fat deposition or hair loss. The results suggest that both somatotrophs and corticotrophs function in the fiber implants.

The hypophysial portal vessels and anterior pituitary gland of adult male Wistar rats were exposed surgically. A hypophysial portal vessel was cannulated and infused for one minute with saline or thyrotrophin (TRH). Anterior pituitary glands were collected at 1,5,15,30 or 60 minutes after cessation of infusion, for light and electron microscopic examination. Before and immediately after cannulation of a portal vessel, a 1-ml sample of blood was collected at 1,5,15,30, or 60 minutes, from the femoral vein for radioimmunoassay (RIA) of growth hormone. Thyrotrophs from anterior pituitary glands of rats infused with TRH displayed emiocytic activity at all time-periods studied. Rough endoplasmic reticular (RER) cisternae were dilated at 15 minutes following infusion and remained dilated at 30 and 60 minutes. TRH was observed to stimulate emiocytic activity in most pituitary cell-types. Extensive dilations of RER cisternae were also observed in mammotrophs and gonadotrophs, but were not observed in somatotrophs or adrenocorticotrophs. The demonstration that thyrotrophs, mammotrophs, somatotrophs, and gonadotrophs respond to TRH suggests that some common features may be shared by these cells. Preliminary analysis of the RIA data show that TRH was potent in elevating radioimmunoassayable growth hormone levels. Significant increases (p less than 0.02) in plasma GH levels were present at the earlier time periods studied (1,5, and 15 minutes) following the infusion of TRH, but no at 30 or 60 minutes. These findings provide additional support for the non-specific action of TRH upon hte various adenohypophysial cell types, and demonstrate that TRH stimulates these cells by a direct action on the adenohypophysis.