The effects of hypothalamic extracts and TRH on the growth and hormone production of GH3 cells in culture

Abstract

Hypothalamic factors were tested for their effects on the production of hormones and the growth of GH3 cells, cloned rat pituitary cells producing prolactin (Prl) and growth hormone (GH). Hypothalamic extracts (HE) (0.05 mg/ml) and TRH (0.3 \g=m\m)stimulated the synthesis of Prl to levels of 306% and 360%, respectively, of the control culture in a medium containing 0.5% foetal bovine serum (FBS) during a 24 h incubation. They did not affect the rate of GH production. The thymidine uptake was suppressed to 57% and 46% of the control by the addition of HE and TRH, respectively. They also inhibited the growth of GH3 to 70% and 74% of the control culture during an 8-day incubation period.On the other hand, LRH affected neither the rate of hormone production nor the thymidine uptake. Somatostatin suppressed the synthesis of Prl and GH, but it did not affect the incorporation of thymidine into the cells. The gel filtration studies of HE revealed that the inhibitory effects of HE on the thymidine uptake were dependent on two substances, TRH and an unknown factor(s) of high molecular nature. The relationship between hormone synthesis and DNA synthesis will be discussed on the basis of the TRH-induced effects on Prl production and DNA synthesis in GH3 cells.Hormonal factors that stimulate the secretion of hormones by endocrine glands or their tumours are generally considered to stimulate proliferation of these cells, as observed in the effect of ACTH upon the adrenal cortex and TSH upon the thy¬ roid gland. As for TRH, it has been reported that it affected the growth of a rat pituitary tumour cell 1 Requests for reprints: The Tokyo Metropolitan Institute of Medical Science, 3-18, Honkomagome, Bunkyoku, Tokyo, 113 Japan. line GH3, a multi hormone-producing cell strain (Hayashi et al. 1978; Clausen et al. 1978; Schon¬ brunn et al. 1980; Brunetetal. 1981). On the other hand, it is not yet known whether hypothalamic factors other than TRH which have either stimula¬ tory or suppressive effects on the release of hor¬ mones from the pituitary gland may affect the growth of this tissue. In the present investigation, the effects of hypo¬ thalamic factors, TRH, LRH, somatostatin and hypothalamic extracts on the proliferation of cells were examined using GH3 cells in comparison with the effects on the release of GH and Prl. Materials and Methods Media and Hormones Tissue culture media, horse serum and foetal bovine serum (FBS) were obtained from Flow Laboratories Co. (Rockville, MD). Synthetic TRH and LRH were gifts from Tanabe Pharmaceutical Co. (Osaka, Japan), and somatostatin and triiodothyronine (T3) were purchased from Sigma Chemical Co. (St. Louis, MO). Rat hypo¬ thalamic extracts (HE) and kits for radioimmunoassay of rat prolactin (Prl) and rat growth hormone (GH) were supplied by the National Institute of Arthritis, Metabo¬ lism and Digestive Disease, USA. Methyl[3H]thymidine, 20 Ci/mmol, and L-proline-2,3,4,5-[3H(N)]TRH, 100 Ci/ mmol, were from New England Nuclear Corp. (Boston, MA). Cell culture GH3 cells were obtained fro...

Effect of activin on production and secretion of prolactin and growth hormone in cultured rat GH3 cells

“…It has been shown that GH3 cells retain their ability to respond to TRH (14), epidermal growth factor (EGF) (15,16) and nerve growth factor (NGF) (17). Recent studies have demonstrated that activin receptors (typeIA, typeII and typeIIB) are present on GH3 cells (18,19).…”