Release of Cyclic Amp From Thyroid Cells in Vitro

Abstract

Half lobes of mouse thyroid gland were incubated in vitro with TSH. They released cyclic AMP (cAMP) into the medium in amounts depending on the concentration of TSH. The release of cAMP was greatest during the first hour of incubation, then it occurred at a lower rate. With an incubation time of 45 min the medium cAMP levels ranged from 43.0 \m=+-\ 11. 9 pmole per mg tissue protein for controls to 296.5 \ m=+-\ 29.2 pmole per mg tissue protein with 5 mU of TSH in the medium.The tissue cAMP level reached a maximum after 15\p=n-\30min of incubation with TSH, then it gradually decreased towards control level during 4 h of incubation. With 25 min of incubation the tissue cAMP level was 28.5 \m=+-\8.8 pmole per mg tissue protein for controls compared to 194.3 \ m=+-\27.0 pmole per mg tissue protein with 5 mU TSH in the incubation medium.The release of thyroxine was of the same order during the later part of the 4 h incubation period compared to the first one. The results illustrate the quantitative importance of cAMP release, and the fact that in the later part of the incubaion period the cell content of cAMP was low while the release of thyroxine remained high.

Plasma cAMP in Normal and Abnormal Human Pregnancy

“…Therefore an explanation comprising the activity of the thyroid gland and h-TSH, HCG and human chorionic TSH effects is more likely in agreement with our observations (Braunstein and Hershman, 1976). The diminished response of T4 and cAMP to TSH in thyroid tissue pretreated with T3, as shown by Gafni et al (1975), as well as the FSHdependent thyroid cAMP release to the plasma (Ahren et al, 1978), are possible explanations for the findings, but not sufficiently proven.…”

“…An HCG-induced ovarian cAMP and progesterone release was mea-sured in ovarian veins in the sheep (fVe/'ss et al, 1978). An example for the in vitro release of cAMP into the incubation medium is the cAMP release from thyroid tissue in amounts depending on the TSH concentration (Ahren et al, 1978). There are some experiments that show a metabolic activity of the tissue by application of cAMP itself, for example the increase of plasma cortisol after dibutyryl-cAMP infusion (Angeli et al, 1973), or the secretion of HCG and estrogens from human trophoblast and term placenta in vitro (Handwerger et al, 1973;Hussa et al, 1974).…”

Factors influencing the release of cyclic AMP from mouse thyroid tissue stimulated by TSH in vitro

“…In this way the accumulated cAMP synthesis in response to a hormone stimula¬ tion may be studied selectively but the cAMP concentrations will be unphysiologically high. Under these conditions thyroid cells stimulated by TSH have been found to respond with an increased synthesis of cAMP that levels off after about 30 min (Rapoport 1976;Ahrén et al 1978). In spite of this the content of cAMP in the cells showed a decreasing tendency from 30 min of stimulation and onwards, principally due to the fact that the nucleotide left the cells (Ahrén et al 1978).…”

“In Vitro” Study on Release of Cyclic AMP and Thyroid Hormone in Autonomously Functioning Thyroid Nodules

“…Final incubation volume was 1.0 ml and triplicate tubes were incubated at 37°C as above. For tissue cyclic AMP generation determination the slices were rapidly immersed in liquid nitrogen, after a 60 min incubation (Ahren, Gustafson, Hedner and Nilsson 1978). After a 300 min incubation, aliquots from the medium were frozen in liquid nitrogen for the released cyclic AMP, T 3 and T 4 assaying (Ahren et al 1978).…”

“…For tissue cyclic AMP generation determination the slices were rapidly immersed in liquid nitrogen, after a 60 min incubation (Ahren, Gustafson, Hedner and Nilsson 1978). After a 300 min incubation, aliquots from the medium were frozen in liquid nitrogen for the released cyclic AMP, T 3 and T 4 assaying (Ahren et al 1978). The cyclic AMP was extracted using a 6% (w/v) perchlorid acid concentration for slices and 12% for the incubation medium.…”