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Requirement for adenosine triphosphate for stimulation in vitro of ox growth-hormone release
Abstract:
Rotenone, carbonyl cyanide chloromethoxyphenylhydrazone and 2,4-dinitrophenol cause parallel falls in ox pituitary ATP content and growth-hormone release in the presence of 65mm-K(+). Carbonyl cyanide chloromethoxyphenylhydrazone (0.4mug/ml) prevented the rise in growth-hormone release, but not the rise in 3':5'-cyclic AMP content after addition of prostaglandin E(2) (1mug/ml). The rate of hormone release from unstimulated slices and from slices in the presence of Ba(2+) at 2.3 or 6.9mm was proportional to the ATP content of the slices. Carbonyl cyanide chloromethoxyphenylhydrazone at concentrations that inhibited release in the presence of the three secretagogues did not alter the pituitary contents of Na(+), K(+) or Ca(2+). The implications of these observations are discussed in terms of the mechanism of stimulus-secretion coupling.
Insights
Pituitary cells release growth hormone when ATP levels drop, a process influenced by various secretagogues. This study explores the link between ATP, cyclic AMP, and hormone release mechanisms.
Area of Science:
- Biochemistry
- Endocrinology
- Cell Biology
Background:
- Adenosine triphosphate (ATP) is crucial for cellular energy and function.
- Growth hormone (GH) release from the pituitary is a complex process involving various signaling pathways.
- Stimulus-secretion coupling describes how external stimuli trigger cellular secretion.
Purpose of the Study:
- To investigate the role of ATP content in regulating ox pituitary growth hormone release.
- To explore the relationship between ATP, cyclic AMP (cAMP), and hormone secretion.
- To elucidate the mechanism of stimulus-secretion coupling in pituitary cells.
Main Methods:
- Experiments utilized ox pituitary slices.
- ATP content and growth hormone release were measured under various conditions.
- Inhibitors like rotenone, carbonyl cyanide chloromethoxyphenylhydrazone (CCCP), and 2,4-dinitrophenol were used.
- Prostaglandin E2 (PGE2) and barium ions (Ba2+) were employed as secretagogues.
Main Results:
- Rotenone, CCCP, and 2,4-dinitrophenol decreased pituitary ATP content and GH release.
- CCCP inhibited PGE2-stimulated GH release but not the rise in cAMP.
- Hormone release rate correlated with ATP content in unstimulated and Ba2+-stimulated slices.
- CCCP did not affect pituitary Na+, K+, or Ca2+ levels.
Conclusions:
- Pituitary GH release is directly proportional to cellular ATP content.
- ATP depletion, rather than cAMP elevation, appears to be a key factor in stimulus-secretion coupling for GH release.
- These findings provide insights into the energy-dependent mechanisms governing pituitary hormone secretion.