Thyrotrophin and growth hormone secretion and cell morphology in hypothyroid pituitary cells cultured on a natural extracellular matrix.

Hypothyroid rat pituitary cells were cultured on an extracellular matrix (ECM) produced by corneal endothelial cells. ECM markedly affected the following parameters. 1) Cell attachment, spreading and proliferation were improved, resulting in a more rapid formation of confluent cell monolayers. 2) In the presence of ECM the production of both thyrotrophin (TSH) and growth hormone (GH) was larger than in its absence. Immunofluorescence studies revealed that 20% of the cells in these monolayers were thyrotrophs; consequently, TSH content was higher while GH level was lower than in control cultures of euthyroid pituitaries. These data suggest that the in vivo physiological differences are maintained by the conditions of the culture. 3) ECM enabled the response of both the somatotrophs and the thyrotrophs to thyrotrophin releasing hormone (TRH) and the cells remained responsive for at least 10 days. Maximal stimulation (1.3- to 6-fold) was obtained with 14 nM of TRH. In the absence of ECM the cells failed to respond to TRH. 4) Cell morphology was examined by scanning electron microscopy (SEM). Cells grown on ECM were characteristically epithelial, whereas those cultured on plastic plates had a fibroblast-like appearance. Four types of cells were identified in the epithelial cell monolayers by the appearance of their surface. TRH induced a 2-fold increase in the number of cells covered with microvilli and a corresponding decrease in the number of smooth surfaced cells. This suggests that hormone secretion is associated with the formation of microvilli.