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Prostaglandin I2 stimulates thyrotropin secretion in vivo and in vitro in rats
Effects of prostaglandin I2 (PG I2) on secretion of thyrotropin (TSH) in vivo and in vitro in rats have been studied. Ten micrograms per kg of PG I2 were injected i. v. and the animals were serially decapitated. Thyrotropin releasing hormone (TRH), thyroxine (T4) and 3,3',5-triiodothyronine (T3) were determined by radioimmunoassay. Effects of PG I2 from anterior pituitary were also investigated by means of an in vitro experiment. Plasma and hypothalamic concentrations of immunoreactive (ir-TRH) did not change after PG I2 injection. Basal plasma TSH levels significantly increased with a peak at 20 min after PG I2 injection. The plasma ir-TRH response to cold did not differ from that of the control, while the plasma TSH response to cold was significantly enhanced by PG I2. The plasma TSH response to TRH was also significantly enhanced by PG I2. The plasma T4h and T3 levels did not change significantly after PG I2 injection. TSH release from anterior pituitary in vitro significantly increased after the addition of PG I2 to medium. These findings suggest that PG I2 stimulates TSH secretion from anterior pituitary in vivo and in vivo in rats.
Effects of prostaglandin I2 (PG I2) on secretion of thyrotropin (TSH) in vivo and in vitro in rats have been studied. Ten micrograms per kg of PG I2 were injected i. v. and the animals were serially decapitated. Thyrotropin releasing hormone (TRH), thyroxine (T4) and 3,3',5-triiodothyronine (T3) were determined by radioimmunoassay. Effects of PG I2 from anterior pituitary were also investigated by means of an in vitro experiment. Plasma and hypothalamic concentrations of immunoreactive (ir-TRH) did not change after PG I2 injection. Basal plasma TSH levels significantly increased with a peak at 20 min after PG I2 injection. The plasma ir-TRH response to cold did not differ from that of the control, while the plasma TSH response to cold was significantly enhanced by PG I2. The plasma TSH response to TRH was also significantly enhanced by PG I2. The plasma T4h and T3 levels did not change significantly after PG I2 injection. TSH release from anterior pituitary in vitro significantly increased after the addition of PG I2 to medium. These findings suggest that PG I2 stimulates TSH secretion from anterior pituitary in vivo and in vivo in rats.