Production and release of thyrotropin and its subunits by monolayer cultures containing XXXX anterior pituitary cells.

@entity1218 @entity6145 @entity291 @entity72839
We have developed a dispersed cell monolayer system derived from @entity291 anterior pituitary glands. Fresh 1- to 6-week-old @entity291 anterior pituitaries were mechanically and enzymatically dispersed and incubated with Dulbecco's Modified Minimal Essential Medium containing 10% hypothyroid goat serum. The media and cell extracts from confluent monolayers were analyzed for @entity291 TSH and free alpha, and @entity72839 subunits by specific homologous RIAs. Basal levels of TSH, free alpha, and free @entity72839 subunits in the media were 6.2 +/- 0.3, and 0.95 +/- 0.05 ng/10(6) cells . 24 h, respectively. Hence, an 8- to 10-fold excess of free alpha over free @entity72839 subunits was released into the medium. Intracellular basal levels of TSH, free alpha, and free @entity72839 subunits were 27.6 +/- 1.7, 10.7 +/- 0.2, and 2.6 +/- 0.3 ng/10(6) cells . 24 h, respectively, and indicated a 3- to 4-fold excess of free alpha over free @entity72839 subunits within the cells. The total alpha-subunit to total beta-subunit ratio was 2:1. @entity1218 stimulated release of TSH and its subunits in a dose-dependent fashion, with a half-maximal dose of 2 nM and a maximal response dose of 10 nM. Stimulation with 100 nM @entity1218 increased the levels of TSH, free alpha, and free @entity72839 subunits (450-900%, 180-200%, and 300-400%, respectively) in medium, with concomitant decreases within cells. Treatment with thyroid hormones decreased basal and blunted @entity1218 -stimulated levels of TSH and its subunits in medium but had no effect on intracellular stores. However, large doses of T4 (25 nM) or T3 (1 nM) did not completely abolish the @entity1218 (100 nM)-stimulated hormone response. @entity1218 and thyroid hormones affect the release of TSH and @entity72839 to a greater extent than they do the alpha-subunit. Finally, total alpha and @entity72839 subunit production was increased with @entity1218 stimulation and decreased with @entity6145 exposure. Thus, an in vitro system to study the net production and secretion of TSH and its subunits in the normal pituitary thyrotrope has been established. (Endocrinology 108: 387, 1981)
